Develop Reference

Is it possible to have a viewpager wrap_content on a simple pager adapter without children

I would like to know if is it possible to have a PagerAdapter with wrap_content without using getChildCount() and getChildAt(i)?
I have checked the answer below, but since on my adapter doesn't have children it doesn't work.
https://stackoverflow.com/a/20784791/10020799
Does someone know how to make an wrap_content adapter in this case?
My PagerAdapter code is:
public class SectionsPagerAdapter extends PagerAdapter {
private Integer pagerTotal = 10;
public SectionsPagerAdapter(Context c) {
super();
inflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void setPagerTotal(Integer item) {
pagerTotal = item;
}
#Override
public int getCount() {
return pagerTotal;
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
LinearLayout layout = (LinearLayout) inflater.inflate(R.layout.home_top_page, null);
container.addView(layout);
topMain = (ImageView) layout.findViewById(R.id.top_main);
if(imageBitmapArray != null && imageBitmapArray.length > 0){
topMain.setImageBitmap(imageBitmapArray[position]);
}else{
if(intImageArray != null) {
topMain.setImageResource(R.drawable.top_main_01);
}
}
return layout;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((View) object);
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view.equals(object);
}
}

You can resize the ViewPager to it's current page size on page swipe from this answer.
You can use the following code:
public class WrapContentViewPager extends ViewPager {
private int mCurrentPagePosition = 0;
public WrapContentViewPager(Context context) {
super(context);
}
public WrapContentViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
try {
boolean wrapHeight = MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST;
if (wrapHeight) {
View child = getChildAt(mCurrentPagePosition);
if (child != null) {
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
int h = child.getMeasuredHeight();
heightMeasureSpec = MeasureSpec.makeMeasureSpec(h, MeasureSpec.EXACTLY);
}
}
} catch (Exception e) {
e.printStackTrace();
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
public void reMeasureCurrentPage(int position) {
mCurrentPagePosition = position;
requestLayout();
}
}
Use it in xml:
<your.package.name.WrapContentViewPager
android:id="#+id/view_pager"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</your.package.name.WrapContentViewPager>
After that call reMeasureCurrentpage function on page swipe.
final WrapContentViewPager wrapContentViewPager = (WrapContentViewPager) findViewById(R.id.view_pager);
wrapContentViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
wrapContentViewPager.reMeasureCurrentPage(wrapContentViewPager.getCurrentItem());
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
Note that a list can have hundreds of items then this is not good to use this wrap_content ViewPager.

Even with a not expandable adapter is possible to use getChildCount() and getChildAt(i) functions.
Based on Khemraj's answer and this post's answer, I was able to solve the problem with the following code:
class:
public class WrapContentViewPager extends ViewPager {
public WrapContentViewPager(Context context) {
super(context);
}
public WrapContentViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int height = 0;
for(int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
int h = child.getMeasuredHeight();
if(h > height) height = h;
}
if (height != 0) {
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
xml:
<your.package.name.WrapContentViewPager
android:id="#+id/view_pager"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</your.package.name.WrapContentViewPager>
on page swipe:
final WrapContentViewPager wrapContentViewPager = (WrapContentViewPager) findViewById(R.id.view_pager);
wrapContentViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
}
#Override
public void onPageScrollStateChanged(int state) {
}
});

How to programmatically reMeasure view?

I have CustomView with 2 RelativeLayouts. There are RecyclerViews in each RelativeLayout. When I add new element to RecyclerView it doesn`t change height.
If I change screen orientation then android measures it well. So my question is how to programmatically tell android that he needs remeasure both childs and parent elements.
requestlayout() and invalidate() doesn`t work
CustomView:
public class ExpandableView extends LinearLayout {
private Settings mSettings ;
private int mExpandState;
private ValueAnimator mExpandAnimator;
private ValueAnimator mParentAnimator;
private AnimatorSet mExpandScrollAnimatorSet;
private int mExpandedViewHeight;
private boolean mIsInit = true;
private int defaultHeight;
private boolean isAllowedExpand = false;
private ScrolledParent mScrolledParent;
private OnExpandListener mOnExpandListener;
public ExpandableView(Context context) {
super(context);
init(null);
}
public ExpandableView(Context context, #Nullable AttributeSet attrs) {
super(context, attrs);
init(attrs);
}
public ExpandableView(Context context, #Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
private void init(AttributeSet attrs) {
Log.w("tag", "init");
setOrientation(VERTICAL);
this.setClipChildren(false);
this.setClipToPadding(false);
mExpandState = ExpandState.PRE_INIT;
mSettings = new Settings();
if(attrs!=null) {
TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.ExpandableView);
mSettings.expandDuration = typedArray.getInt(R.styleable.ExpandableView_expDuration, Settings.EXPAND_DURATION);
mSettings.expandWithParentScroll = typedArray.getBoolean(R.styleable.ExpandableView_expWithParentScroll,false);
mSettings.expandScrollTogether = typedArray.getBoolean(R.styleable.ExpandableView_expExpandScrollTogether,true);
typedArray.recycle();
}
}
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
Log.w("tag", "onMeasure");
Log.w("tag", "widthMeasureSpec - " + widthMeasureSpec);
Log.w("tag", "heightMeasureSpec - " + heightMeasureSpec);
int childCount = getChildCount();
if(childCount!=2) {
throw new IllegalStateException("ExpandableLayout must has two child view !");
}
if(mIsInit) {
((MarginLayoutParams)getChildAt(0).getLayoutParams()).bottomMargin=0;
MarginLayoutParams marginLayoutParams = ((MarginLayoutParams)getChildAt(1).getLayoutParams());
marginLayoutParams.bottomMargin=0;
marginLayoutParams.topMargin=0;
marginLayoutParams.height = 0;
mExpandedViewHeight = getChildAt(1).getMeasuredHeight();
defaultHeight = mExpandedViewHeight;
mIsInit =false;
mExpandState = ExpandState.CLOSED;
View view = getChildAt(0);
if (view != null){
view.setOnClickListener(v -> toggle());
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
#Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
Log.w("tag", "onSizeChanged");
if(mSettings.expandWithParentScroll) {
mScrolledParent = Utils.getScrolledParent(this);
}
}
private int getParentScrollDistance () {
int distance = 0;
Log.w("tag", "getParentScrollDistance");
if(mScrolledParent == null) {
return distance;
}
distance = (int) (getY() + getMeasuredHeight() + mExpandedViewHeight - mScrolledParent.scrolledView.getMeasuredHeight());
for(int index = 0; index < mScrolledParent.childBetweenParentCount; index++) {
ViewGroup parent = (ViewGroup) getParent();
distance+=parent.getY();
}
return distance;
}
private void verticalAnimate(final int startHeight, final int endHeight ) {
int distance = getParentScrollDistance();
final View target = getChildAt(1);
mExpandAnimator = ValueAnimator.ofInt(startHeight,endHeight);
mExpandAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
#Override
public void onAnimationUpdate(ValueAnimator animation) {
target.getLayoutParams().height = (int) animation.getAnimatedValue();
target.requestLayout();
}
});
mExpandAnimator.addListener(new AnimatorListenerAdapter() {
#Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
if(endHeight-startHeight < 0) {
mExpandState = ExpandState.CLOSED;
if (mOnExpandListener != null) {
mOnExpandListener.onExpand(false);
}
} else {
mExpandState=ExpandState.EXPANDED;
if(mOnExpandListener != null) {
mOnExpandListener.onExpand(true);
}
}
}
});
mExpandState=mExpandState==ExpandState.EXPANDED?ExpandState.CLOSING :ExpandState.EXPANDING;
mExpandAnimator.setDuration(mSettings.expandDuration);
if(mExpandState == ExpandState.EXPANDING && mSettings.expandWithParentScroll && distance > 0) {
mParentAnimator = Utils.createParentAnimator(mScrolledParent.scrolledView, distance, mSettings.expandDuration);
mExpandScrollAnimatorSet = new AnimatorSet();
if(mSettings.expandScrollTogether) {
mExpandScrollAnimatorSet.playTogether(mExpandAnimator,mParentAnimator);
} else {
mExpandScrollAnimatorSet.playSequentially(mExpandAnimator,mParentAnimator);
}
mExpandScrollAnimatorSet.start();
} else {
mExpandAnimator.start();
}
}
public void setExpand(boolean expand) {
if (mExpandState == ExpandState.PRE_INIT) {return;}
getChildAt(1).getLayoutParams().height = expand ? mExpandedViewHeight : 0;
requestLayout();
mExpandState=expand?ExpandState.EXPANDED:ExpandState.CLOSED;
}
public boolean isExpanded() {
return mExpandState==ExpandState.EXPANDED;
}
public void toggle() {
if (isAllowedExpand){
if(mExpandState==ExpandState.EXPANDED) {
close();
}else if(mExpandState==ExpandState.CLOSED) {
expand();
}
}
}
public void expand() {
verticalAnimate(0,mExpandedViewHeight);
}
public void close() {
verticalAnimate(mExpandedViewHeight,0);
}
public interface OnExpandListener {
void onExpand(boolean expanded) ;
}
public void setOnExpandListener(OnExpandListener onExpandListener) {
this.mOnExpandListener = onExpandListener;
}
public void setExpandScrollTogether(boolean expandScrollTogether) {
this.mSettings.expandScrollTogether = expandScrollTogether;
}
public void setExpandWithParentScroll(boolean expandWithParentScroll) {
this.mSettings.expandWithParentScroll = expandWithParentScroll;
}
public void setExpandDuration(int expandDuration) {
this.mSettings.expandDuration = expandDuration;
}
#Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
Log.w("tag", "onDetachedFromWindow");
if(mExpandAnimator!=null&&mExpandAnimator.isRunning()) {
mExpandAnimator.cancel();
mExpandAnimator.removeAllUpdateListeners();
}
if(mParentAnimator!=null&&mParentAnimator.isRunning()) {
mParentAnimator.cancel();
mParentAnimator.removeAllUpdateListeners();
}
if(mExpandScrollAnimatorSet!=null) {
mExpandScrollAnimatorSet.cancel();
}
}
public void setAllowedExpand(boolean allowedExpand) {
isAllowedExpand = allowedExpand;
}
public void increaseDistance(int size){
if(mExpandState==ExpandState.EXPANDED) {
close();
}
mExpandedViewHeight = defaultHeight + size;
}
//func just for loggs
public void showParams(){
RelativeLayout relativeLayout = (RelativeLayout) getChildAt(1);
/*relativeLayout.requestLayout();
relativeLayout.invalidate();*/
RecyclerView recyclerView = (RecyclerView) relativeLayout.getChildAt(1);
Log.d("tag", "height - " + relativeLayout.getHeight());
Log.d("tag", "childs - " + relativeLayout.getChildCount());
Log.d("tag", "recycler height - " + recyclerView.getHeight());
recyclerView.requestLayout();
recyclerView.invalidateItemDecorations();
recyclerView.invalidate();
RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
layoutManager.getHeight();
Log.d("tag", " layoutManager.getHeight() - " + layoutManager.getHeight());
layoutManager.requestLayout();
layoutManager.generateDefaultLayoutParams();
layoutManager.onItemsChanged(recyclerView);
Log.d("tag", " layoutManager.getHeight()2- " + layoutManager.getHeight());
layoutManager.getChildCount();
recyclerView.getChildCount();
Log.d("tag", "manager childs - " + layoutManager.getChildCount());
Log.d("tag", "recycler childs - " + recyclerView.getChildCount());
}
}
Layout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:background="#color/grey_light_color"
>
<com.example.develop.project.Utils.ExpandableView.ExpandableView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/test_custom_view"
app:expWithParentScroll="true"
android:layout_gravity="center"
android:background="#color/grey_color"
>
<android.support.v7.widget.CardView
android:id="#+id/start_card"
android:layout_width="match_parent"
android:layout_height="70dp"
android:background="#color/white_color"
android:layout_marginTop="5dp"
android:layout_marginStart="5dp"
android:layout_marginEnd="5dp"
>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/stage_tv4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#color/grey_deep_color"
android:text="Запуск"
android:layout_centerVertical="true"
android:layout_marginStart="15dp"
android:textSize="18sp"
/>
</RelativeLayout>
</android.support.v7.widget.CardView>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/start_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/start_accept"
android:textSize="18sp"
android:layout_marginStart="15dp"
android:layout_marginTop="15dp"
android:layout_marginBottom="15dp"
android:textColor="#color/grey_deep_color"
android:layout_marginEnd="15dp"
/>
<android.support.v7.widget.RecyclerView
android:id="#+id/my_test_tv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#id/start_tv"
android:layout_marginTop="10dp"
android:layout_marginStart="15dp"
android:layout_marginEnd="15dp"
>
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
</com.example.develop.project.Utils.ExpandableView.ExpandableView>
<Button
android:id="#+id/add_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true"
android:text="Add elem"
android:layout_marginStart="15dp"
android:layout_marginBottom="15dp"
/>
<Button
android:id="#+id/check_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:text="Check params"
android:layout_marginBottom="15dp"
android:layout_marginEnd="15dp"
/>
</RelativeLayout>
Activity:
public class TestActivity extends MvpAppCompatActivity implements TestContract.View {
TestAdapter testAdapter;
#InjectPresenter
public TestPresenter presenter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test_layout);
init();
}
private void init() {
ExpandableView expandableView = findViewById(R.id.test_custom_view);
expandableView.setAllowedExpand(true);
Button add_btn = findViewById(R.id.add_btn);
Button check_btn = findViewById(R.id.check_btn);
add_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
presenter.addElem();
}
});
check_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
expandableView.showParams();
}
});
}
#Override
public void addElems(ArrayList<String> list) {
testAdapter.notifyDataSetChanged();
}
#Override
public void populateAdapter(ArrayList<String> list) {
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
RecyclerView recyclerView = findViewById(R.id.my_test_tv);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setNestedScrollingEnabled(false);
recyclerView.setHasFixedSize(false);
testAdapter = new TestAdapter(list);
recyclerView.setAdapter(testAdapter);
}
}
Adapter:
public class TestAdapter extends RecyclerView.Adapter<TestAdapter.TasksViewHolder> {
private List<String> list;
public TestAdapter(List<String> list) {
this.list = list;
}
#NonNull
#Override
public TestAdapter.TasksViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.test_item, parent, false);
TestAdapter.TasksViewHolder vh = new TestAdapter.TasksViewHolder(v);
return vh;
}
#Override
public void onBindViewHolder(#NonNull TestAdapter.TasksViewHolder holder, int position) {
String text = list.get(position);
holder.textView.setText(text);
}
public static class TasksViewHolder extends RecyclerView.ViewHolder {
private TextView textView;
public TasksViewHolder(View itemView) {
super(itemView);
textView = itemView.findViewById(R.id.my_test_tv);
}
}
#Override
public int getItemCount() {
return list.size();
}
}

The ExpandableView contains some suspicious code in its onMeasure method.
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
...
if(mIsInit) {
((MarginLayoutParams)getChildAt(0).getLayoutParams()).bottomMargin=0;
MarginLayoutParams marginLayoutParams = ((MarginLayoutParams)getChildAt(1).getLayoutParams());
marginLayoutParams.bottomMargin=0;
marginLayoutParams.topMargin=0;
marginLayoutParams.height = 0;
mExpandedViewHeight = getChildAt(1).getMeasuredHeight();
defaultHeight = mExpandedViewHeight;
mIsInit =false;
mExpandState = ExpandState.CLOSED;
View view = getChildAt(0);
if (view != null){
view.setOnClickListener(v -> toggle());
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
The mIsInit variable is set to true on creation and than to false when onMeasure is called for the first time. So the code in the condition runs only once.
But it stores value mExpandedViewHeight obtained as getChildAt(1).getMeasuredHeight() and that is current height of your relative layout, which contains (still empty) RecyclerView.
As far as I can see there's nothing in ExpadableView's code that would update this value, when you add an item to the Recylerview.
I am not sure, what would the correct/perfect implementation of the onMeasure method be (for your component). That would require some debugging and testing of the component, and perhaps some tweaks in other parts of the code.
If you wrote the component, you may want to invest more effort into debugging. If you didn't write the component, you should try to find other one, that is properly implemented. Custom components with custom measurements are an advanced topic.
If you really want to go with debugging and fixing your component, that first thing to do is to update the mExpandedViewHeight value on every measurement, but that might require updating other values that are derived from this value.

Implement an scroll to select an item ListView

I want to use an ListView where you scroll the list to select an item.
It should be like a Seekbar but the thumb should be fixed and you must use the bar to adjust it. One problem am facing is, I have no idea how this kind of widget is called, making it hard for me to search. So I made this image below to give you an better idea. And to be fair, I don't even know if this is the right title for this kind of feature.
I usually see this kind of interface in clock setting (see below image)

Reference scroll horizontal at https://stackoverflow.com/a/38411582/5887320 by use RecyclerView instead of ListView.
This is my customize code to get virtical scroll :
1.dimens.xml
<dimen name="item_dob_width">100dp</dimen>
<dimen name="item_dob_height">50dp</dimen>
2.recyclerview_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center">
<TextView
android:id="#+id/tv_year"
android:layout_width="#dimen/item_dob_width"
android:layout_height="#dimen/item_dob_height"
android:textColor="#android:color/white"
android:background="#android:color/darker_gray"
android:textSize="28sp"
android:gravity="center"/>
</LinearLayout>
3.recyclerview.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"/>
</LinearLayout>
4.MainActivity.java
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.widget.TextView;
import java.util.ArrayList;
public class MainActivity extends Activity{
private static final String TAG = MainActivity.class.getSimpleName();
public float firstItemHeightDate;
public float paddingDate;
public float itemHeightDate;
public int allPixelsDate;
public int finalHeightDate;
private DateAdapter dateAdapter;
private ArrayList<LabelerDate> labelerDates = new ArrayList<>();
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.recyclerview);
getRecyclerviewDate();
}
public void getRecyclerviewDate() {
final RecyclerView recyclerViewDate = (RecyclerView) findViewById(R.id.recycler_view);
if (recyclerViewDate != null) {
recyclerViewDate.postDelayed(new Runnable() {
#Override
public void run() {
setDateValue();
}
}, 300);
/*recyclerViewDate.postDelayed(new Runnable() {
#Override
public void run() {
recyclerViewDate.smoothScrollToPosition(dateAdapter.getItemCount()-1);
setDateValue();
}
}, 5000);*/
}
ViewTreeObserver vtoDate = recyclerViewDate.getViewTreeObserver();
vtoDate.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
recyclerViewDate.getViewTreeObserver().removeOnPreDrawListener(this);
finalHeightDate = recyclerViewDate.getMeasuredHeight();
itemHeightDate = getResources().getDimension(R.dimen.item_dob_height);
paddingDate = (finalHeightDate - itemHeightDate) / 2;
firstItemHeightDate = paddingDate;
allPixelsDate = 0;
final LinearLayoutManager dateLayoutManager = new LinearLayoutManager(getApplicationContext());
dateLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerViewDate.setLayoutManager(dateLayoutManager);
recyclerViewDate.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
synchronized (this) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
calculatePositionAndScrollDate(recyclerView);
}
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
allPixelsDate += dy;
}
});
if (labelerDates == null) {
labelerDates = new ArrayList<>();
}
genLabelerDate();
dateAdapter = new DateAdapter(labelerDates, (int) firstItemHeightDate);
recyclerViewDate.setAdapter(dateAdapter);
dateAdapter.setSelecteditem(dateAdapter.getItemCount() - 1);
return true;
}
});
}
private void genLabelerDate() {
for (int i = 0; i < 32; i++) {
LabelerDate labelerDate = new LabelerDate();
labelerDate.setNumber(Integer.toString(i));
labelerDates.add(labelerDate);
if (i == 0 || i == 31) {
labelerDate.setType(DateAdapter.VIEW_TYPE_PADDING);
} else {
labelerDate.setType(DateAdapter.VIEW_TYPE_ITEM);
}
}
}
/* this if most important, if expectedPositionDate < 0 recyclerView will return to nearest item*/
private void calculatePositionAndScrollDate(RecyclerView recyclerView) {
int expectedPositionDate = Math.round((allPixelsDate + paddingDate - firstItemHeightDate) / itemHeightDate);
if (expectedPositionDate == -1) {
expectedPositionDate = 0;
} else if (expectedPositionDate >= recyclerView.getAdapter().getItemCount() - 2) {
expectedPositionDate--;
}
scrollListToPositionDate(recyclerView, expectedPositionDate);
}
/* this if most important, if expectedPositionDate < 0 recyclerView will return to nearest item*/
private void scrollListToPositionDate(RecyclerView recyclerView, int expectedPositionDate) {
float targetScrollPosDate = expectedPositionDate * itemHeightDate + firstItemHeightDate - paddingDate;
float missingPxDate = targetScrollPosDate - allPixelsDate;
if (missingPxDate != 0) {
//recyclerView.smoothScrollBy((int) missingPxDate, 0);//horizontal
recyclerView.smoothScrollBy(0, (int) missingPxDate);//virtical
}
setDateValue();
}
//
private void setDateValue() {
int expectedPositionDateColor = Math.round((allPixelsDate + paddingDate - firstItemHeightDate) / itemHeightDate);
int setColorDate = expectedPositionDateColor + 1;
//set color here
dateAdapter.setSelecteditem(setColorDate);
}
public class DateAdapter extends RecyclerView.Adapter<DateAdapter.DateViewHolder> {
private ArrayList<LabelerDate> dateDataList;
private static final int VIEW_TYPE_PADDING = 1;
private static final int VIEW_TYPE_ITEM = 2;
private int paddingHeightDate = 0;
private int selectedItem = -1;
public DateAdapter(ArrayList<LabelerDate> dateData, int paddingHeightDate) {
this.dateDataList = dateData;
this.paddingHeightDate = paddingHeightDate;
}
#Override
public DateViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (viewType == VIEW_TYPE_ITEM) {
final View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_item,
parent, false);
return new DateViewHolder(view);
} else {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_item,
parent, false);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) view.getLayoutParams();
layoutParams.height = paddingHeightDate;
view.setLayoutParams(layoutParams);
return new DateViewHolder(view);
}
}
#Override
public void onBindViewHolder(DateViewHolder holder, int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (getItemViewType(position) == VIEW_TYPE_ITEM) {
holder.tvDate.setText(labelerDate.getNumber());
holder.tvDate.setVisibility(View.VISIBLE);
Log.d(TAG, "default " + position + ", selected " + selectedItem);
if (position == selectedItem) {
Log.d(TAG, "center" + position);
holder.tvDate.setTextColor(Color.parseColor("#76FF03"));
holder.tvDate.setTextSize(35);
} else {
holder.tvDate.setTextColor(Color.BLACK);
holder.tvDate.setTextSize(18);
}
} else {
holder.tvDate.setVisibility(View.INVISIBLE);
}
}
public void setSelecteditem(int selecteditem) {
this.selectedItem = selecteditem;
notifyDataSetChanged();
}
#Override
public int getItemCount() {
return dateDataList.size();
}
#Override
public int getItemViewType(int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (labelerDate.getType() == VIEW_TYPE_PADDING) {
return VIEW_TYPE_PADDING;
} else {
return VIEW_TYPE_ITEM;
}
}
public class DateViewHolder extends RecyclerView.ViewHolder {
public TextView tvDate;
public DateViewHolder(View itemView) {
super(itemView);
tvDate = (TextView) itemView.findViewById(R.id.tv_year);
}
}
}
private class LabelerDate {
private int type;
private String number;
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
}
}

Get center visible item of RecycleView when scrolling

This is what I want:
As image above, I want to draw a center line on RecycleView, then get the center item when scrolling (as well as move left or right)
Here is my try to draw a horizontal RecycleView:
HorizontalAdapter adapter = new HorizontalAdapter(data);
LinearLayoutManager layoutManager
= new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
recycleView.setLayoutManager(layoutManager);
recycleView.setAdapter(adapter);
Is there any way to know which item is moved to the center of RecycleView? And how can I scroll RecycleView to left or right just one position?
Update: I tried to use a scroll listener to get the middle position, but it doesn't work as an aspect.
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int firstPos = layoutManager.findFirstVisibleItemPosition();
int lastPos = layoutManager.findLastVisibleItemPosition();
int middle = Math.abs(lastPos - firstPos) / 2 + firstPos;
int selectedPos = -1;
for (int i = 0; i < adapter.getItemCount(); i++) {
if (i == middle) {
adapter.getItem(i).setSelected(true);
selectedPos = i;
} else {
adapter.getItem(i).setSelected(false);
}
}
adapter.notifyDataSetChanged();
}
And get the result:
I only want to change the selected item (make text to white color) when it is on the blue Rect

I made something just like this. I can do exactly what you need.
First of all, this is how is my alogrithm work
This is my recyclerView Adapter
public class DateAdapter extends RecyclerView.Adapter<DateAdapter.DateViewHolder> {
private ArrayList<LabelerDate> dateDataList;
private static final int VIEW_TYPE_PADDING = 1;
private static final int VIEW_TYPE_ITEM = 2;
private int paddingWidthDate = 0;
private int selectedItem = -1;
public DateAdapter(ArrayList<LabelerDate> dateData, int paddingWidthDate) {
this.dateDataList = dateData;
this.paddingWidthDate = paddingWidthDate;
}
#Override
public DateViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (viewType == VIEW_TYPE_ITEM) {
final View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_date,
parent, false);
return new DateViewHolder(view);
} else {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_padding,
parent, false);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) view.getLayoutParams();
layoutParams.width = paddingWidthDate;
view.setLayoutParams(layoutParams);
return new DateViewHolder(view);
}
}
#Override
public void onBindViewHolder(DateViewHolder holder, int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (getItemViewType(position) == VIEW_TYPE_ITEM) {
if(labelerDate.dateType.equals(BirthDayActivity.DateType.C31))
holder.tvDate.setText(String.valueOf(labelerDate.valueDate));
holder.tvDate.setVisibility(View.VISIBLE);
holder.imgSmall.setVisibility(View.VISIBLE);
if (position == selectedItem) {
holder.tvDate.setTextColor(Color.parseColor("#094673"));
holder.tvDate.setTextSize(35);
holder.imgSmall.setBackgroundResource(R.color.textviewbold);
} else {
holder.tvDate.setTextColor(Color.GRAY);
holder.tvDate.setTextSize(35);
holder.imgSmall.setBackgroundResource(R.color.gray);
}
}
}
public void setSelecteditem(int selecteditem) {
this.selectedItem = selecteditem;
notifyDataSetChanged();
}
#Override
public int getItemCount() {
return dateDataList.size();
}
#Override
public int getItemViewType(int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (labelerDate.dateType.equals(BirthDayActivity.DateType.NONE)) {
return VIEW_TYPE_PADDING;
}
return VIEW_TYPE_ITEM;
}
public class DateViewHolder extends RecyclerView.ViewHolder {
public TextView tvDate;
public ImageView imgSmall;
public DateViewHolder(View itemView) {
super(itemView);
tvDate = (TextView) itemView.findViewById(R.id.tvNumberDate);
imgSmall = (ImageView) itemView.findViewById(R.id.small_marked_dob);
}
}}
This is most important alogrithm:
public void getRecyclerviewDate() {
recyclerViewDate = (RecyclerView) findViewById(R.id.recyclerViewDay);
ViewTreeObserver vtoDate = recyclerViewDate.getViewTreeObserver();
vtoDate.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
recyclerViewDate.getViewTreeObserver().removeOnPreDrawListener(this);
finalWidthDate = recyclerViewDate.getMeasuredWidth();
itemWidthDate = getResources().getDimension(R.dimen.item_dob_width);
paddingDate = (finalWidthDate - itemWidthDate) / 2;
firstItemWidthDate = paddingDate ;
allPixelsDate = 0;
final LinearLayoutManager dateLayoutManager = new LinearLayoutManager(getApplicationContext());
dateLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerViewDate.setLayoutManager(dateLayoutManager);
recyclerViewDate.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
synchronized (this) {
if(newState == RecyclerView.SCROLL_STATE_IDLE){
calculatePositionAndScrollDate(recyclerView);
}
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
allPixelsDate += dx;
}
});
if (labelerDates == null)
labelerDates = new ArrayList<>();
labelerDates.addAll(genLabelerDate(currentMonth, currentYear));
dateAdapter = new DateAdapter(labelerDates, (int) firstItemWidthDate);
recyclerViewDate.setAdapter(dateAdapter);
return true;
}
});
}
/* this if most important, if expectedPositionDate < 0 recyclerView will return to nearest item*/
private void calculatePositionAndScrollDate(RecyclerView recyclerView) {
int expectedPositionDate = Math.round((allPixelsDate + paddingDate - firstItemWidthDate) / itemWidthDate);
if (expectedPositionDate == -1) {
expectedPositionDate = 0;
} else if (expectedPositionDate >= recyclerView.getAdapter().getItemCount() - 2) {
expectedPositionDate--;
}
scrollListToPositionDate(recyclerView, expectedPositionDate);
}
/* this if most important, if expectedPositionDate < 0 recyclerView will return to nearest item*/
private void scrollListToPositionDate(RecyclerView recyclerView, int expectedPositionDate) {
float targetScrollPosDate = expectedPositionDate * itemWidthDate + firstItemWidthDate - paddingDate;
float missingPxDate = targetScrollPosDate - allPixelsDate;
if (missingPxDate != 0) {
recyclerView.smoothScrollBy((int) missingPxDate, 0);
}
}
private void setDateValue() {
int expectedPositionDateColor = Math.round((allPixelsDate + paddingDate - firstItemWidthDate) / itemWidthDate);
setColorDate = expectedPositionDateColor + 1;
//set color here
dateAdapter.setSelecteditem(setColorDate);
}
#Override
protected void onRestoreInstanceState(#NonNull Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
allPixelsDate = savedInstanceState.getFloat(BUNDLE_LIST_PIXELS_DATE);
allPixelsDateChanged = savedInstanceState.getFloat(BUNDLE_LIST_PIXELS_DATE_CHANGED);
}
#Override
protected void onSaveInstanceState(#NonNull Bundle outState) {
super.onSaveInstanceState(outState);
outState.putFloat(BUNDLE_LIST_PIXELS_DATE, allPixelsDate);
outState.putFloat(BUNDLE_LIST_PIXELS_DATE_CHANGED, allPixelsDateChanged);
}
And this is my result:
Look at this video link, this is my app demo

Sometimes is needed the entire example code block together, because we may miss something. Here is what I have, feel free to correct anything since I may be doing some little mistake somewhere. And Yes, this answer is an extension of #tranhieu answer. Thanks #tranhieu.
MainActivity.java
package com.test;
import android.app.Activity;
import android.graphics.Color;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.widget.TextView;
import java.util.ArrayList;
public class MainActivity extends Activity {
private static final String TAG = MainActivity.class.getSimpleName();
public float firstItemWidthDate;
public float paddingDate;
public float itemWidthDate;
public int allPixelsDate;
public int finalWidthDate;
private DateAdapter dateAdapter;
private ArrayList<LabelerDate> labelerDates = new ArrayList<>();
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getRecyclerviewDate();
}
public void getRecyclerviewDate() {
final RecyclerView recyclerViewDate = (RecyclerView) findViewById(R.id.rv_tasks_date);
if (recyclerViewDate != null) {
recyclerViewDate.postDelayed(new Runnable() {
#Override
public void run() {
setDateValue();
}
}, 300);
recyclerViewDate.postDelayed(new Runnable() {
#Override
public void run() {
recyclerViewDate.smoothScrollToPosition(dateAdapter.getItemCount()-1);
setDateValue();
}
}, 5000);
}
ViewTreeObserver vtoDate = recyclerViewDate.getViewTreeObserver();
vtoDate.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
recyclerViewDate.getViewTreeObserver().removeOnPreDrawListener(this);
finalWidthDate = recyclerViewDate.getMeasuredWidth();
itemWidthDate = getResources().getDimension(R.dimen.item_dob_width);
paddingDate = (finalWidthDate - itemWidthDate) / 2;
firstItemWidthDate = paddingDate;
allPixelsDate = 0;
final LinearLayoutManager dateLayoutManager = new LinearLayoutManager(getApplicationContext());
dateLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerViewDate.setLayoutManager(dateLayoutManager);
recyclerViewDate.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
synchronized (this) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
calculatePositionAndScrollDate(recyclerView);
}
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
allPixelsDate += dx;
}
});
if (labelerDates == null) {
labelerDates = new ArrayList<>();
}
genLabelerDate();
dateAdapter = new DateAdapter(labelerDates, (int) firstItemWidthDate);
recyclerViewDate.setAdapter(dateAdapter);
dateAdapter.setSelecteditem(dateAdapter.getItemCount() - 1);
return true;
}
});
}
private void genLabelerDate() {
for (int i = 0; i < 32; i++) {
LabelerDate labelerDate = new LabelerDate();
labelerDate.setNumber(Integer.toString(i));
labelerDates.add(labelerDate);
if (i == 0 || i == 31) {
labelerDate.setType(DateAdapter.VIEW_TYPE_PADDING);
} else {
labelerDate.setType(DateAdapter.VIEW_TYPE_ITEM);
}
}
}
/* this if most important, if expectedPositionDate < 0 recyclerView will return to nearest item*/
private void calculatePositionAndScrollDate(RecyclerView recyclerView) {
int expectedPositionDate = Math.round((allPixelsDate + paddingDate - firstItemWidthDate) / itemWidthDate);
if (expectedPositionDate == -1) {
expectedPositionDate = 0;
} else if (expectedPositionDate >= recyclerView.getAdapter().getItemCount() - 2) {
expectedPositionDate--;
}
scrollListToPositionDate(recyclerView, expectedPositionDate);
}
/* this if most important, if expectedPositionDate < 0 recyclerView will return to nearest item*/
private void scrollListToPositionDate(RecyclerView recyclerView, int expectedPositionDate) {
float targetScrollPosDate = expectedPositionDate * itemWidthDate + firstItemWidthDate - paddingDate;
float missingPxDate = targetScrollPosDate - allPixelsDate;
if (missingPxDate != 0) {
recyclerView.smoothScrollBy((int) missingPxDate, 0);
}
setDateValue();
}
//
private void setDateValue() {
int expectedPositionDateColor = Math.round((allPixelsDate + paddingDate - firstItemWidthDate) / itemWidthDate);
int setColorDate = expectedPositionDateColor + 1;
// set color here
dateAdapter.setSelecteditem(setColorDate);
}
public class DateAdapter extends RecyclerView.Adapter<DateAdapter.DateViewHolder> {
private ArrayList<LabelerDate> dateDataList;
private static final int VIEW_TYPE_PADDING = 1;
private static final int VIEW_TYPE_ITEM = 2;
private int paddingWidthDate = 0;
private int selectedItem = -1;
public DateAdapter(ArrayList<LabelerDate> dateData, int paddingWidthDate) {
this.dateDataList = dateData;
this.paddingWidthDate = paddingWidthDate;
}
#Override
public DateViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (viewType == VIEW_TYPE_ITEM) {
final View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item,
parent, false);
return new DateViewHolder(view);
} else {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item,
parent, false);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) view.getLayoutParams();
layoutParams.width = paddingWidthDate;
view.setLayoutParams(layoutParams);
return new DateViewHolder(view);
}
}
#Override
public void onBindViewHolder(DateViewHolder holder, int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (getItemViewType(position) == VIEW_TYPE_ITEM) {
holder.tvDate.setText(labelerDate.getNumber());
holder.tvDate.setVisibility(View.VISIBLE);
Log.d(TAG, "default " + position + ", selected " + selectedItem);
if (position == selectedItem) {
Log.d(TAG, "center" + position);
holder.tvDate.setTextColor(Color.parseColor("#76FF03"));
holder.tvDate.setTextSize(35);
} else {
holder.tvDate.setTextColor(Color.WHITE);
holder.tvDate.setTextSize(18);
}
} else {
holder.tvDate.setVisibility(View.INVISIBLE);
}
}
public void setSelecteditem(int selecteditem) {
this.selectedItem = selecteditem;
notifyDataSetChanged();
}
#Override
public int getItemCount() {
return dateDataList.size();
}
#Override
public int getItemViewType(int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (labelerDate.getType() == VIEW_TYPE_PADDING) {
return VIEW_TYPE_PADDING;
} else {
return VIEW_TYPE_ITEM;
}
}
public class DateViewHolder extends RecyclerView.ViewHolder {
public TextView tvDate;
public DateViewHolder(View itemView) {
super(itemView);
tvDate = (TextView) itemView.findViewById(R.id.txt_date);
}
}
}
private class LabelerDate {
private int type;
private String number;
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.RecyclerView
android:id="#+id/rv_tasks_date"
android:layout_width="match_parent"
android:layout_height="48dp" />
<ImageView
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_gravity="center"
android:layout_marginTop="48dp"
android:src="#android:drawable/ic_dialog_info" />
</FrameLayout>
</LinearLayout>
item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="wrap_content"
android:layout_height="match_parent">
<TextView
android:id="#+id/txt_date"
android:layout_width="#dimen/item_dob_width"
android:layout_height="48dp"
android:text="32"
android:textColor="#android:color/white"
android:background="#android:color/darker_gray"
android:textSize="28sp"
android:gravity="center"/>
</LinearLayout>
dimens.xml
<resources>
<dimen name="item_dob_width">100dp</dimen>
</resources>

Oh boy. I've been searching for this answer for almost a week and then found out the solution. Custom LayoutManagers? No. ItemDecorator? Nope.
Here's the easiest way to do it:
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:paddingStart="150dp"
android:paddingEnd="150dp"
android:clipToPadding="false" />
The critical part is:
android:paddingStart="150dp"
android:paddingEnd="150dp"
android:clipToPadding="false"
And then just assign SnapHelper to your RecylcerView:
val snapHelper = LinearSnapHelper()
snapHelper.attachToRecyclerView(recyclerView)
This is it. The easiest and most perfect solution to the problem

I'm used the SnapHelper right here:
// init snaphelper
SnapHelper snapHelper = new LinearSnapHelper();
snapHelper.attachToRecyclerView(recyclerView)
// init layout manager
LinearLayoutManager layoutManager = new LinearLayoutManager(mainActivity);
layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(layoutManager);
// init adapter
adatper.setSnapHelper(snapHelper);
adatper.setLayoutManager(layoutManager);
adatper.initAdapter(new Float((DisplayHelper.getDisplayWidth(mainActivity) / 2) - (fooViewWidth / 2)).intValue());
recyclerView.setAdapter(adatper);
As said by TranHieu the solution of inserting 2 item for padding (at start and at end positions) is good.
I don't like the use of ViewTreeObserver because of poor readability of code. With this technique then you must also manage redrawing of the items if they are recycled.
If you are using customview classes you can set its width directly into these classes.
For example this is my padding class
/**
* Created by firegloves on 25/09/15.
*/
#EViewGroup(R.layout.view_padding)
public class PaddingView extends FooView {
Context mCtx;
public PaddingView(Context context) {
super(context);
mCtx = context;
}
public void setWidth(int width) {
setLayoutParams(new LayoutParams(width, ViewGroup.LayoutParams.WRAP_CONTENT));
}
}
In my adapter I store the desired padding item width, that is equal to (displayWidth / 2) - (realItemWidth / 2)
This is my adapter, don't look at methods not matching RecyclerView.Adapter, pay attention to the initAdapter method and to the onCreateItemView method
#EBean
public class FooAdapterRecycler extends RecyclerViewAdapterBase<Foo, FooView> {
private final int TYPE_PADDING_VIEW = 0;
private final int TYPE_REAL_VIEW = 1;
#RootContext
Context ctx;
#Bean(Finder.class)
IFinder finder;
SnapHelper snapHelper;
RecyclerView.LayoutManager layoutManager;
private int paddingWidth = 0;
/**
* preleva i dati dal finder
*/
public void initAdapter(int paddingWidth) {
/*******************************
* THIS CODE IS THE IMPORTANT ONE
******************************/
this.paddingWidth = paddingWidth;
// add 1 item for initial space
mItems = new ArrayList<>();
Foo foo = new Foo();
mItems.add(foo);
// get real items from finder
mItems.addAll(finder.findAll());
// add 1 item for final space
mItems = new ArrayList<>();
Foo foo2 = new Foo();
mItems.add(foo2);
}
#Override
public int getItemViewType(int position) {
if (position == 0 || position == getItemCount()-1) {
return TYPE_PADDING_VIEW;
} else {
return TYPE_REAL_VIEW;
}
}
#Override
protected FooView onCreateItemView(ViewGroup parent, int viewType) {
/*******************************
* THIS CODE IS THE IMPORTANT ONE
******************************/
if (viewType == TYPE_PADDING_VIEW) {
PaddingView view = PaddingView_.build(ctx);
view.setWidth(paddingWidth);
return view;
} else {
return FooView_.build(ctx);
}
}
public void setSnapHelper(SnapHelper snapHelper) {
this.snapHelper = snapHelper;
}
public void setLayoutManager(RecyclerView.LayoutManager layoutManager) {
this.layoutManager = layoutManager;
}
}
I'm using AndroidAnnotations library but it's not required
Hope that helps

USING SNAPHELPER - A SMOOTHER SOLUTION
Here it is another solution using SnapHelper. Starting from the answer of #TranHieu here:
https://stackoverflow.com/a/34647005/3944251
and the compressed by #sector11 here:
https://stackoverflow.com/a/38411582/3944251
I wrote the following code which is also based in both answers above, but it's simpler and offers a smoother solution using SnapHelper presented in android support library 24.2.0.
Here you have the MainActivity class. The rest is the same with #sector11's answer.
import android.graphics.Color;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.LinearSnapHelper;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.widget.TextView;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
public float firstItemWidthDate;
public float itemWidthDate;
public int allPixelsDate;
public int finalWidthDate;
private DateAdapter dateAdapter;
private ArrayList<LabelerDate> labelerDates;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
labelerDates = new ArrayList<>();
getRecyclerviewDate();
}
public void getRecyclerviewDate() {
final RecyclerView recyclerViewDate = (RecyclerView) findViewById(R.id.rv_tasks_date);
recyclerViewDate.postDelayed(new Runnable() {
#Override
public void run() {
//recyclerViewDate.smoothScrollToPosition(dateAdapter.getItemCount()-1);
setDateValue();
}
}, 300);
ViewTreeObserver vtoDate = recyclerViewDate.getViewTreeObserver();
vtoDate.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
recyclerViewDate.getViewTreeObserver().removeOnPreDrawListener(this);
finalWidthDate = recyclerViewDate.getMeasuredWidth();
itemWidthDate = getResources().getDimension(R.dimen.item_dob_width);
firstItemWidthDate = (finalWidthDate - itemWidthDate) / 2;
allPixelsDate = 0;
final LinearLayoutManager dateLayoutManager = new LinearLayoutManager(getApplicationContext());
dateLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerViewDate.setLayoutManager(dateLayoutManager);
/* Create a LinearSnapHelper and attach the recyclerView to it. */
final LinearSnapHelper snapHelper = new LinearSnapHelper();
snapHelper.attachToRecyclerView(recyclerViewDate);
recyclerViewDate.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
allPixelsDate += dx;
recyclerView.post(new Runnable() {
public void run() {
setDateValue();
}
});
}
});
genLabelerDate();
dateAdapter = new DateAdapter(labelerDates, (int) firstItemWidthDate);
recyclerViewDate.setAdapter(dateAdapter);
dateAdapter.setSelecteditem(dateAdapter.getItemCount() - 1);
return true;
}
});
}
private void genLabelerDate() {
for (int i = 0; i < 32; i++) {
LabelerDate labelerDate = new LabelerDate();
labelerDate.setNumber(Integer.toString(i));
labelerDates.add(labelerDate);
if (i == 0 || i == 31) {
labelerDate.setType(DateAdapter.VIEW_TYPE_PADDING);
} else {
labelerDate.setType(DateAdapter.VIEW_TYPE_ITEM);
}
}
}
//
private void setDateValue() {
int expectedPositionDateColor = Math.round(allPixelsDate / itemWidthDate);
int setColorDate = expectedPositionDateColor + 1;
// set color here
dateAdapter.setSelecteditem(setColorDate);
}
public class DateAdapter extends RecyclerView.Adapter<DateAdapter.DateViewHolder> {
private ArrayList<LabelerDate> dateDataList;
private static final int VIEW_TYPE_PADDING = 1;
private static final int VIEW_TYPE_ITEM = 2;
private int paddingWidthDate = 0;
private int selectedItem = -1;
public DateAdapter(ArrayList<LabelerDate> dateData, int paddingWidthDate) {
this.dateDataList = dateData;
this.paddingWidthDate = paddingWidthDate;
}
#Override
public DateAdapter.DateViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
if (viewType == VIEW_TYPE_PADDING) {
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) view.getLayoutParams();
layoutParams.width = paddingWidthDate;
view.setLayoutParams(layoutParams);
}
return new DateViewHolder(view);
}
#Override
public void onBindViewHolder(DateAdapter.DateViewHolder holder, int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (getItemViewType(position) == VIEW_TYPE_ITEM) {
holder.tvDate.setText(labelerDate.getNumber());
holder.tvDate.setVisibility(View.VISIBLE);
Log.d(TAG, "default " + position + ", selected " + selectedItem);
if (position == selectedItem) {
Log.d(TAG, "center" + position);
holder.tvDate.setTextColor(Color.parseColor("#76FF03"));
holder.tvDate.setTextSize(35);
} else {
holder.tvDate.setTextColor(Color.WHITE);
holder.tvDate.setTextSize(18);
}
} else {
holder.tvDate.setVisibility(View.INVISIBLE);
}
}
public void setSelecteditem(int selecteditem) {
this.selectedItem = selecteditem;
notifyDataSetChanged();
}
#Override
public int getItemCount() {
return dateDataList.size();
}
#Override
public int getItemViewType(int position) {
LabelerDate labelerDate = dateDataList.get(position);
if (labelerDate.getType() == VIEW_TYPE_PADDING) {
return VIEW_TYPE_PADDING;
} else {
return VIEW_TYPE_ITEM;
}
}
public class DateViewHolder extends RecyclerView.ViewHolder {
public TextView tvDate;
public DateViewHolder(View itemView) {
super(itemView);
tvDate = (TextView) itemView.findViewById(R.id.txt_date);
}
}
}
private class LabelerDate {
private int type;
private String number;
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
}
}

You can use a LinearSnapHelper
Attach to your recyclerView like
val snapHelper = LinearSnapHelper()
snapHelper.attachToRecyclerView(this)
Then, to get the center view, use
snapHelper.findSnapView(horizontalScrollView.layoutManager)?

As mentioned in the other answer, there is no direct way to do this.
This is probably how you can achieve what you described in the question.
Know the number of items visible on the screen.
Select the middle item programmatically every time the view is scrolled.
Keep a partially transparent image as an overlay on the middle item on the recyclerview. (You'll need to compute the coordinates based on the width of the recycler view or width of the screen and the width of the overlay image you choose to put.
Refresh the selected value in a text view below the recycler view every time there is a scroll.
The image overlays have to be placed in a way they appear connected and as one single control.

For this feature use EcoGallery library:
https://github.com/falnatsheh/EcoGallery

At first, I needed something similar, not this. But I was able to adapt #TranHieu solution to my needs, so I voted up his solution.
I wanted to create full-screen horizontal recyclerview that after user sroll updates scrollPosition to mostVisibleItem.
setup:
private void setUpScrolling() {
mRecyclerVIew.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
mRecyclerVIew.getViewTreeObserver().removeOnPreDrawListener(this);
CustomScrollListener listener = (CustomScrollListener) mScrollListener;
listener.width = mRecyclerVIew.getMeasuredWidth();
listener.dx = 0;
return true;
}
});
}
listener:
private class CustomScrollListener extends OnScrollListener {
private int mLastDx = 0;
int width = 0;
int dx = 0;
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
if (mLastDx != dx) {
scrollToMostVisibleItem();
} else {
dx = 0;
mLastDx = 0;
}
}
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
this.dx += dx;
}
private void scrollToMostVisibleItem() {
int direction = (dx > 0) ? 1 : -1;
dx = Math.abs(dx);
int shiftCount = Math.round(dx / width);
int pixelShift = dx % width;
if (pixelShift > width / 2) {
shiftCount++;
}
float targetScrollPixels = shiftCount * width;
float finalScrollPixels = (targetScrollPixels - dx) * direction;
if (finalScrollPixels != 0) {
mRecyclerVIew.smoothScrollBy((int) finalScrollPixels, 0);
mLastDx = (int) finalScrollPixels;
dx = 0;
}
}
}

I used another approach in my case.
you can find the deatils here: RecyclerView - How highlight central visible item during scroll1
In my opinion, my solution is more easy than the others.

If someone is looking for a more generic implementation, here is my code based on the answers of this thread:
Add the CenterLinearSnapHelper
public class CenterLinearSnapHelper extends LinearSnapHelper {
//Constants
public static final String TAG = CenterLinearSnapHelper.class.getSimpleName();
//Attributes
private Context context;
private float itemWidth;
private OnPaddingComputationListener listener;
//Constructors
/**
* A linear snap helper which helps centering the items in a recyclerview.
*
* #param itemWidth The (fixed) width of a child view in pixels.
*/
public CenterLinearSnapHelper(float itemWidth) {
this.itemWidth = itemWidth;
}
public void attachToRecyclerView(#Nullable RecyclerView recyclerView,
#NonNull OnPaddingComputationListener listener) throws IllegalStateException {
this.listener = listener;
//Calculates the padding for the first and end item
calculatePadding(recyclerView);
//Create a LinearSnapHelper and attach the recyclerView to it.
attachToRecyclerView(recyclerView);
}
public float getItemWidth() {
return itemWidth;
}
private void calculatePadding(RecyclerView recyclerView) {
if (recyclerView == null)
return;
ViewTreeObserver observer = recyclerView.getViewTreeObserver();
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
recyclerView.getViewTreeObserver().removeOnPreDrawListener(this);
int finalWidth = recyclerView.getMeasuredWidth();
float padding = (finalWidth - itemWidth) / 2;
listener.onPadding(padding, finalWidth);
return true;
}
});
}
public interface OnPaddingComputationListener {
void onPadding(float padding, int finalWidth);
}
}
In your Activity/Fragment where you create your RecyclerView:
float itemWidth = getResources().getDimension(R.dimen.favorite_room_width);
CenterLinearSnapHelper snapHelper = new CenterLinearSnapHelper(itemWidth);
snapHelper.attachToRecyclerView(binding.listFavorites, (padding, finalWidth) -> {
//Set the adapter
roomAdapter = new RoomAdapter(requireContext(), rooms);
roomAdapter.addPaddingItems((int) padding);
roomAdapter.setOnToggleClickListener(FavoritesFragment.this);
binding.listFavorites.setAdapter(roomAdapter);
});
In your adapter:
public void addPaddingItems(int padding) {
if (padding < 0)
throw new IllegalStateException("Padding cannot be smaller than 0");
this.padding = padding;
//Add 2 new items as the first and last
//NOTE: If you update your existing dataset (e.g add new items), you should redo the calculation!
rooms.add(0, new Room("First"));
rooms.add(rooms.size(), new Room("Last"));
}
#Override
public int getItemViewType(int position) {
if (padding >= 0 && (position == 0 || position == rooms.size() - 1)) {
return VIEW_TYPE_PADDING;
}
return VIEW_TYPE_ITEM;
}
#NonNull
#Override
public RoomViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
ViewFavoriteRoomBinding binding = DataBindingUtil.inflate(inflater, R.layout.view_favorite_room, parent, false);
if (viewType == VIEW_TYPE_PADDING) {
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) binding.getRoot().getLayoutParams();
layoutParams.width = padding;
binding.getRoot().setLayoutParams(layoutParams);
}
RoomViewHolder viewHolder = new RoomViewHolder(context, binding, onToggleClickListener);
viewHolder.getRecyclerView().setRecycledViewPool(viewPool);
return viewHolder;
}

How to create scrollable page of carousels in Android?

I am attempting to build a UI for my Android app which contains a vertically scrollable page of horizontally scrollable carousels (something like what the Netflix app does). How is this type of behaviour accomplished?
A basic implementation would be enough to get me started. There are a few other requirements for the UI, which I'll include here for reference, since it may impact what classes or libraries I can use.
1) Vertical scrolling between carousels should be smooth, but when user releases, the UI should "snap to" the closest carousel (so the user is always on a carousel row, not between two carousels).
2) Horizontal scrolling on a carousel should be smooth, but when user releases, the UI should "snap to" the closest item in the carousel.
3) Should be possible to overlay additional information over an item in the carousel
4) UI should be adaptable to any screen size.
5) Should be navigable with the arrow keys (for touchscreen-less devices)
6) Should work on a wide range of Android versions (possibly through the support library)
7) Should be OK to use in an open-source app licensed under the GPL
Acceptable answers DO NOT have to meet all of these requirements. At a minimum, a good answer should involve navigating multiple carousels (versus only one carousel).
Here is a mock-up of basically what I am envisioning (I'm flexible, doesn't have to look like this.. point is just to clarify what I am talking about -- each row would contain a lot of items that could be scrolled left and right, and the whole page could be scrolled up and down)

Main Idea
In order to have a flexible design and having unlimited items you can create a RecyclerView as a root view with a LinearLayoutManager.VERTICAL as a LayoutManager. for each row you can put another RecyclerView but now with a LinearLayoutManager.HORIZONTAL as a LayoutManager.
Result
Source
Code
Requirements
1) Vertical scrolling between carousels should be smooth, but when
user releases, the UI should "snap to" the closest carousel (so the
user is always on a carousel row, not between two carousels).
2) Horizontal scrolling on a carousel should be smooth, but when user
releases, the UI should "snap to" the closest item in the carousel.
In order to achieve those I used OnScrollListener and when the states goes SCROLL_STATE_IDLE I check top and bottom views to see which of them has more visible region then scroll to that position. for each rows I do so for left and right views for each row adapter. In this way always one side of your carousels or rows fit. for example if top is fitted the bottom is not or vise versa. I think if you play a little more you can achieve that but you must know the dimension of window and change the dimension of carousels at runtime.
3) Should be possible to overlay additional information over an item
in the carousel
If you use RelativeLayout or FrameLayout as a root view of each item you can put information on top of each other. as you can see the numbers are on the top of images.
4) UI should be adaptable to any screen size.
if you know how to support multiple screen size you can do so easily, if you do not know read the document.
Supporting Multiple Screens
5) Should be navigable with the arrow keys (for touchscreen-less
devices)
use below function
mRecyclerView.scrollToPosition(position);
6) Should work on a wide range of Android versions (possibly through
the support library)
import android.support.v7.widget.RecyclerView;
7) Should be OK to use in an open-source app licensed under the GPL
Ok
happy coding!!

You can use ListView with a custom OnTouchListener (for snapping items) for the vertical scrolling and TwoWayGridView again with a custom OnTouchListener (for snapping items)
main.xml
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/containerList"
android:layout_width="match_parent"
android:layout_height="300dp"
android:background="#E8E8E8"
android:divider="#android:color/transparent"
android:dividerHeight="16dp" />
list_item_hgrid.xml
<com.jess.ui.TwoWayGridView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/grid"
android:layout_width="match_parent"
android:layout_height="160dp"
android:layout_marginBottom="16dp"
app:cacheColorHint="#E8E8E8"
app:columnWidth="128dp"
app:gravity="center"
app:horizontalSpacing="16dp"
app:numColumns="auto_fit"
app:numRows="1"
app:rowHeight="128dp"
app:scrollDirectionLandscape="horizontal"
app:scrollDirectionPortrait="horizontal"
app:stretchMode="spacingWidthUniform"
app:verticalSpacing="16dp" />
And the Activity code will be something like the following
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test);
ListView containerList = (ListView) findViewById(R.id.containerList);
containerList.setAdapter(new DummyGridsAdapter(this));
containerList.setOnTouchListener(mContainerListOnTouchListener);
}
private View.OnTouchListener mContainerListOnTouchListener = new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_UP:
View itemView = ((ListView) view).getChildAt(0);
int top = itemView.getTop();
if (Math.abs(top) >= itemView.getHeight() / 2) {
top = itemView.getHeight() - Math.abs(top);
}
((ListView) view).smoothScrollBy(top, 400);
}
return false;
}
};
And here are the test adapters
private static class DummyGridsAdapter extends BaseAdapter {
private Context mContext;
private TwoWayGridView[] mChildGrid;
public DummyGridsAdapter(Context context) {
mContext = context;
mChildGrid = new TwoWayGridView[getCount()];
for (int i = 0; i < mChildGrid.length; i++) {
mChildGrid[i] = (TwoWayGridView) LayoutInflater.from(context).
inflate(R.layout.list_item_hgrid, null);
mChildGrid[i].setAdapter(new DummyImageAdapter(context));
mChildGrid[i].setOnTouchListener(mChildGridOnTouchListener);
}
}
#Override
public int getCount() {
return 8;
}
#Override
public Object getItem(int position) {
return position;
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
return mChildGrid[position];
}
private View.OnTouchListener mChildGridOnTouchListener = new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_UP:
View itemView = ((TwoWayGridView) view).getChildAt(0);
int left = itemView.getLeft();
if (Math.abs(left) >= itemView.getWidth() / 2) {
left = itemView.getWidth() - Math.abs(left);
}
((TwoWayGridView) view).smoothScrollBy(left, 400);
}
return false;
}
};
}
private static class DummyImageAdapter extends BaseAdapter {
private Context mContext;
private final int mDummyViewWidthHeight;
public DummyImageAdapter(Context context) {
mContext = context;
mDummyViewWidthHeight = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 128,
context.getResources().getDisplayMetrics());
}
#Override
public int getCount() {
return 16;
}
#Override
public Object getItem(int position) {
int component = (getCount() - position - 1) * 255 / getCount();
return Color.argb(255, 255, component, component);
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView = new ImageView(mContext);
imageView.setBackgroundColor((Integer) getItem(position));
imageView.setLayoutParams(new TwoWayGridView.LayoutParams(mDummyViewWidthHeight, mDummyViewWidthHeight));
return imageView;
}
}

I would suggest the Recycler view.
You can create horizontal and vertical list or gridviews. In my opinion the viewpager can become complicated at times.
I'm working on video on demand application and this saved me.
In your case it will be easy to set up. I will give you some code.
You will need the following:
XML View - Where the recycle layout is declared.
Adapter - You will need a view to populate the adapter and fill the recycleview.
Creating the view
<android.support.v7.widget.RecyclerView
android:id="#+id/recycle_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="none"
android:orientation="horizontal"
android:gravity="center"
android:overScrollMode="never"/>
Declare this where you want the carousel to display.
Next you want to create the adapter:
public class HorizontalCarouselItemAdapter extends RecyclerView.Adapter<HorizontalCarouselItemAdapter.ViewHolder> {
List<objects> items;
int itemLayout;
public HorizontalCarouselItemAdapter(Context context, int itemLayout, List<objects> items) {
this.context = context;
this.itemLayout = itemLayout;
this.items = items;
}
#Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(itemLayout, parent, false);
return new ViewHolder(v);
}
#Override public void onBindViewHolder(final ViewHolder holder, final int position) {
this.holders = holder;
final GenericAsset itemAdapter = items.get(position);
holder.itemImage.setDrawable //manipulate variables here
}
#Override public int getItemCount() {
return items.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public ImageView itemImage;
public ViewHolder(View itemView) {
super(itemView);
itemImage = (ImageView) itemView.findViewById(R.id.carousel_cell_holder_image);
}
}
This is where you feed the data to the adapter to populate each carousel item.
Finally declare it and call the adapter:
recyclerView = (RecyclerView)findViewById(R.id.recycle_view);
ListLayoutManager manager = new ListLayoutManager(getApplication(), ListLayoutManager.Orientation.HORIZONTAL);
recyclerView.setLayoutManager(manager);
CustomAdpater adapter = new CustomAdapter(getApplication(), data);
recyclerView.setAdapter(adapter);
You can create a listview with recycle views to achieve what you want.
This class is great for smooth scrolling and memory optimisation.
This is the link for it:
https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html
I hope this helps you.

You can use a ScrollView as parent inside that ScrollView place a Vertical LinearLayout in for loop inflate a layout which consist coverflow for carousel effect
github link of android-coverflow

I needed somthing like that a while back, I just used that : https://github.com/simonrob/Android-Horizontal-ListView
Simple, powerful, customizable.
Example of my version :
public class HorizontalListView extends AdapterView<ListAdapter> {
public boolean mAlwaysOverrideTouch = true;
protected ListAdapter mAdapter;
private int mLeftViewIndex = -1;
private int mRightViewIndex = 0;
protected int mCurrentX;
protected int mNextX;
private int mMaxX = Integer.MAX_VALUE;
private int mDisplayOffset = 0;
protected Scroller mScroller;
private GestureDetector mGesture;
private Queue<View> mRemovedViewQueue = new LinkedList<View>();
private OnItemSelectedListener mOnItemSelected;
private OnItemClickListener mOnItemClicked;
private OnItemLongClickListener mOnItemLongClicked;
private boolean mDataChanged = false;
public HorizontalListView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
private synchronized void initView() {
mLeftViewIndex = -1;
mRightViewIndex = 0;
mDisplayOffset = 0;
mCurrentX = 0;
mNextX = 0;
mMaxX = Integer.MAX_VALUE;
mScroller = new Scroller(getContext());
mGesture = new GestureDetector(getContext(), mOnGesture);
}
#Override
public void setOnItemSelectedListener(AdapterView.OnItemSelectedListener listener) {
mOnItemSelected = listener;
}
#Override
public void setOnItemClickListener(AdapterView.OnItemClickListener listener) {
mOnItemClicked = listener;
}
#Override
public void setOnItemLongClickListener(AdapterView.OnItemLongClickListener listener) {
mOnItemLongClicked = listener;
}
private DataSetObserver mDataObserver = new DataSetObserver() {
#Override
public void onChanged() {
synchronized (HorizontalListView.this) {
mDataChanged = true;
}
invalidate();
requestLayout();
}
#Override
public void onInvalidated() {
reset();
invalidate();
requestLayout();
}
};
#Override
public ListAdapter getAdapter() {
return mAdapter;
}
#Override
public View getSelectedView() {
//TODO: implement
return null;
}
#Override
public void setAdapter(ListAdapter adapter) {
if (mAdapter != null) {
mAdapter.unregisterDataSetObserver(mDataObserver);
}
mAdapter = adapter;
mAdapter.registerDataSetObserver(mDataObserver);
reset();
}
private synchronized void reset() {
initView();
removeAllViewsInLayout();
requestLayout();
}
#Override
public void setSelection(int position) {
//TODO: implement
}
private void addAndMeasureChild(final View child, int viewPos) {
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
}
addViewInLayout(child, viewPos, params, true);
child.measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.AT_MOST),
MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.AT_MOST));
}
#Override
protected synchronized void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (mAdapter == null) {
return;
}
if (mDataChanged) {
int oldCurrentX = mCurrentX;
initView();
removeAllViewsInLayout();
mNextX = oldCurrentX;
mDataChanged = false;
}
if (mScroller.computeScrollOffset()) {
mNextX = mScroller.getCurrX();
}
if (mNextX <= 0) {
mNextX = 0;
mScroller.forceFinished(true);
}
if (mNextX >= mMaxX) {
mNextX = mMaxX;
mScroller.forceFinished(true);
}
int dx = mCurrentX - mNextX;
removeNonVisibleItems(dx);
fillList(dx);
positionItems(dx);
mCurrentX = mNextX;
if (!mScroller.isFinished()) {
post(new Runnable() {
#Override
public void run() {
requestLayout();
}
});
}
}
private void fillList(final int dx) {
int edge = 0;
View child = getChildAt(getChildCount() - 1);
if (child != null) {
edge = child.getRight();
}
fillListRight(edge, dx);
edge = 0;
child = getChildAt(0);
if (child != null) {
edge = child.getLeft();
}
fillListLeft(edge, dx);
}
private void fillListRight(int rightEdge, final int dx) {
while (rightEdge + dx < getWidth() && mRightViewIndex < mAdapter.getCount()) {
View child = mAdapter.getView(mRightViewIndex, mRemovedViewQueue.poll(), this);
addAndMeasureChild(child, -1);
rightEdge += child.getMeasuredWidth();
if (mRightViewIndex == mAdapter.getCount() - 1) {
mMaxX = mCurrentX + rightEdge - getWidth();
}
if (mMaxX < 0) {
mMaxX = 0;
}
mRightViewIndex++;
}
}
private void fillListLeft(int leftEdge, final int dx) {
while (leftEdge + dx > 0 && mLeftViewIndex >= 0) {
View child = mAdapter.getView(mLeftViewIndex, mRemovedViewQueue.poll(), this);
addAndMeasureChild(child, 0);
leftEdge -= child.getMeasuredWidth();
mLeftViewIndex--;
mDisplayOffset -= child.getMeasuredWidth();
}
}
private void removeNonVisibleItems(final int dx) {
View child = getChildAt(0);
while (child != null && child.getRight() + dx <= 0) {
mDisplayOffset += child.getMeasuredWidth();
mRemovedViewQueue.offer(child);
removeViewInLayout(child);
mLeftViewIndex++;
child = getChildAt(0);
}
child = getChildAt(getChildCount() - 1);
while (child != null && child.getLeft() + dx >= getWidth()) {
mRemovedViewQueue.offer(child);
removeViewInLayout(child);
mRightViewIndex--;
child = getChildAt(getChildCount() - 1);
}
}
private void positionItems(final int dx) {
if (getChildCount() > 0) {
mDisplayOffset += dx;
int left = mDisplayOffset;
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
int childWidth = child.getMeasuredWidth();
child.layout(left, 0, left + childWidth, child.getMeasuredHeight());
left += childWidth;
}
}
}
public synchronized void scrollTo(int x) {
mScroller.startScroll(mNextX, 0, x - mNextX, 0);
requestLayout();
}
public synchronized void scrollToChild(int position) {
//TODO
requestLayout();
}
#Override
public boolean dispatchTouchEvent(MotionEvent ev) {
return mGesture.onTouchEvent(ev);
}
protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
synchronized (HorizontalListView.this) {
mScroller.fling(mNextX, 0, (int) -velocityX, 0, 0, mMaxX, 0, 0);
}
requestLayout();
return true;
}
protected boolean onDown(MotionEvent e) {
mScroller.forceFinished(true);
return true;
}
private OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {
#Override
public boolean onDown(MotionEvent e) {
return HorizontalListView.this.onDown(e);
}
#Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
float velocityY) {
return HorizontalListView.this.onFling(e1, e2, velocityX, velocityY);
}
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
synchronized (HorizontalListView.this) {
mNextX += (int) distanceX;
}
requestLayout();
return true;
}
#Override
public boolean onSingleTapConfirmed(MotionEvent e) {
Rect viewRect = new Rect();
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
int left = child.getLeft();
int right = child.getRight();
int top = child.getTop();
int bottom = child.getBottom();
viewRect.set(left, top, right, bottom);
if (viewRect.contains((int) e.getX(), (int) e.getY())) {
if (mOnItemClicked != null) {
mOnItemClicked.onItemClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId(mLeftViewIndex + 1 + i));
}
if (mOnItemSelected != null) {
mOnItemSelected.onItemSelected(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId(mLeftViewIndex + 1 + i));
}
break;
}
}
return true;
}
#Override
public void onLongPress(MotionEvent e) {
Rect viewRect = new Rect();
int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
View child = getChildAt(i);
int left = child.getLeft();
int right = child.getRight();
int top = child.getTop();
int bottom = child.getBottom();
viewRect.set(left, top, right, bottom);
if (viewRect.contains((int) e.getX(), (int) e.getY())) {
if (mOnItemLongClicked != null) {
mOnItemLongClicked.onItemLongClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId(mLeftViewIndex + 1 + i));
}
break;
}
}
}
};
}
Here is the XML :
<com.example.package.widgets.HorizontalListView
android:id="#+id/horizontal_listview"
android:layout_marginTop="30dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_width="fill_parent"
android:layout_height="80dp"
android:background="#color/light_gray"
/>
In the OnCreate :
mAdapter = new ArrayAdapter<Uri>(this, R.layout.viewitem) {
#Override
public int getCount() {
return listUriAdapter.size();
}
#Override
public Uri getItem(int position) {
return listUriAdapter.get(position);
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(final int position, View convertView, ViewGroup parent) {
// do what you have to do
return retval;
}
};
onItemClickListener = new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
}
};
onItemLongClickListener = new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
return false;
}
};
horizontalListView.setOnItemClickListener(onItemClickListener);
horizontalListView.setOnItemLongClickListener(onItemLongClickListener);
horizontalListView.setAdapter(mAdapter);