Develop Reference

RecyclerView in ConstraintLayout. Show only complety visible items on a screen

I need to create a horizontal list of items that only displays fully visible items.
But as you can see, my recycler view show a particular element. I use a horizontal LinearLayoutManager.
I add 10 elements, but recycler view has room only for 3. I need to show only 3, but it always show me 3 and particular element.
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycler"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintEnd_toStartOf="#+id/textView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
My item layout:
<LinearLayout
android:id="#+id/itemLayout"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="10dp">
<TextView
android:id="#+id/tvAnimalName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ASDAS"
android:background="#color/colorAccent"
android:padding="10dp"
android:textSize="17sp"/>
</LinearLayout>
Adapter and activity are plain.
How can I show only visible 3 items?
Edit.
I must to disable scroll. So i am using:
layoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false) {
#Override
public boolean canScrollHorizontally() {
return false;
}
};
Edit 2. These methods show -1 always:
int findLastVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();

class HideLastDecorator() : RecyclerView.ItemDecoration() {
override fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State) {
super.onDraw(c, parent, state)
val count = parent.childCount
for (i in 0 until count) {
parent.getChildAt(i).visibility = if (count == i - 1) View.INVISIBLE else View.VISIBLE
}
}
}
and add it to your recyclerView Decorations
appsRecyclerView.addItemDecoration(HideLastDecorator())
Sorry for Kotlin :)
View.INVISIBLE is important, because if the View becomes GONE, it will be removed from the measuring of the RecyclerView's content and the new ViewHolder would be added.
I prefer to work careful with OnClickListener if any is set for the ViewHolder's content.

Below code will work for you. A little explanation: Extend RecyclerView and override onLayout() method. Once RecyclerView is ready iterate through all visible (on-screen) children of RecyclerView and apply your logic. In our case we'll draw BounddingBox for every nth child and RecyclerView. If child's bounds lie inside RecyclerView's bounds then show that child otherwise set visibility to GONE/INVISIBLE.
public class CustomRecyclerView extends RecyclerView {
Rect recyclerViewBounds = new Rect();
Rect currentChildViewBounds = new Rect();
public CustomRecyclerView(#NonNull Context context) {
super(context);
}
public CustomRecyclerView(#NonNull Context context, #Nullable AttributeSet attrs) {
super(context, attrs);
}
public CustomRecyclerView(#NonNull Context context, #Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
recyclerViewBounds.set(l, t, r, b);
for (int i = 0; i < getChildCount(); i++) {
View currentChild = getChildAt(i);
currentChildViewBounds.set(currentChild.getLeft(), currentChild.getTop(), currentChild.getRight(), currentChild.getBottom());
currentChild.setVisibility(recyclerViewBounds.contains(currentChildViewBounds) ? VISIBLE : GONE); // or INVISBLE instead of GONE
}
}
}
And most importantly: In your xml file use com.your.packagename.CustomRecyclerView instead of androidx.recyclerview.widget.RecyclerView.
NOTE: Please refrain from any object initialization inside onLayout(). What I mean is don't move the object initializations inside onLayout() to make it "fancier".

None of the proposed answer worked as expected, so there ItemDecoration that i made, it checks if view completely visible in layout manager, and hide rest of views
class HideNotFullyVisibleDecorator : RecyclerView.ItemDecoration() {
override fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State) {
super.onDraw(c, parent, state)
val count = parent.childCount
for (i in 0 until count) {
val currentChild = parent.getChildAt(i)
currentChild.visibility =
if (parent.layoutManager?.isViewPartiallyVisible(currentChild, true, false) == true)
View.VISIBLE
else
View.GONE
}
}
}
Usage: recycler.addItemDecoration(HideNotFullyVisibleDecorator())
Also in my case I disabled scrolling for recycler

Recycler view is a Scrollable container which holds viewholders and recycles on scroll-up and down,
So it will display as much data as possible on screen, and that fourth half-visible item that you've shown in screenshot is just default behaviour of every scrollable view in android.
You have to customize your viewholders to adjust accordingly on runtime so that only fully visible items should be rendered.
You can do something like:
val availableWidth = screenWidth - (textViewWidth)
val itemWidth = (availableWidth / 3)

Get child view height in RecyclerView ItemDecoration.getItemOffsets

I am attempting to create an ItemDecoration that will maintain a minimum height for a RecyclerView by dynamically adding padding to the last item.
To calculate the amount of padding I need to know the total height of all children. I am approximating this by getting the height of a single view and multiplying it by the number of items in the Adapter.
The problem I am experiencing is that view.getHeight() doesn't always return the correct height. Usually the first time getItemOffsets() is called the height is much smaller than it should be (e.g. 30px vs 300px). This happens even if I give the child views a fixed height in the layout XML. I am guessing this has something to do with the measure/layout cycle by I am unsure of how to get the correct view dimensions in the ItemDecoration.
What is the correct way to get the child views height programmatically in getItemOffsets()?
ItemDecoration:
public class MinHeightPaddingItemDecoration extends RecyclerView.ItemDecoration {
private static final String LOG_TAG = MinHeightPaddingItemDecoration.class.getSimpleName();
private int mMinHeight;
public MinHeightPaddingItemDecoration(int minHeight) {
super();
mMinHeight = minHeight;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView recyclerView, RecyclerView.State state) {
int itemCount = state.getItemCount();
int lastPosition = itemCount - 1;
int itemPosition = recyclerView.getChildAdapterPosition(view);
int layoutPosition = recyclerView.getChildLayoutPosition(view);
// If this view isnt on screen then do nothing
if (layoutPosition != RecyclerView.NO_POSITION && itemPosition == lastPosition) {
// NOTE: view.getHeight() doesn't always return the correct height, even if the layout is given a fixed height in the XML
int childHeight = view.getHeight();
int totalChildHeight = childHeight * itemCount;
int minHeight = getMinHeight();
if (totalChildHeight < minHeight) {
outRect.bottom = minHeight - totalChildHeight;
}
}
}
private int getMinHeight() {
return mMinHeight;
}
}
recycler_view_item.xml
<?xml version="1.0" encoding="utf-8"?>
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable name="controller" type="my.ViewController"/>
</data>
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_gravity="center"
android:clickable="true"
android:onClick="#{() -> controller.doSomething()}">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Child layout"
/>
</RelativeLayout>
</android.support.v7.widget.CardView>
</layout>

I found this workaround for fixed sized child views. I am still not sure how to handle dynamically sized layouts.
// NOTE: view.getHeight() doesn't always return the correct height
// NOTE: even if the layout is given a fixed height in the XML.
// NOTE: Instead directly access the LayoutParams height value
int childHeight = view.getLayoutParams().height;

I found a kind-of hack, after reading https://yoda.entelect.co.za/view/9627/how-to-android-recyclerview-item-decorations.
Before calculating padding based on child.width, I manually measure the View, if needed:
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
if(view.width == 0) fixLayoutSize(view, parent)
calculatePadding(outRect, view, parent, state)
}
private fun fixLayoutSize(view: View, parent: ViewGroup) {
if (view.layoutParams == null) {
view.layoutParams = ViewGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT
)
}
val widthSpec = View.MeasureSpec.makeMeasureSpec(parent.width, View.MeasureSpec.EXACTLY)
val heightSpec = View.MeasureSpec.makeMeasureSpec(parent.height, View.MeasureSpec.UNSPECIFIED)
val childWidth = ViewGroup.getChildMeasureSpec(
widthSpec, parent.paddingLeft + parent.paddingRight, view.layoutParams.width
)
val childHeight = ViewGroup.getChildMeasureSpec(
heightSpec, parent.paddingTop + parent.paddingBottom, view.layoutParams.height
)
view.measure(childWidth, childHeight)
view.layout(0, 0, view.measuredWidth, view.measuredHeight)
}

Android how to use recyclerview to scroll horizontally in large vertical data set

I want to use recylerview to show a large vertical data set with a large amount of data on each row
I am currently using the LinearLayoutManager
Each row has it's own ViewHolder where I hold a "RowView" object. Each RowView is a fixed width.
public class EventsRecylerAdapter extends RecyclerView.Adapter<EventsRecylerAdapter.ViewHolder>
{
private Context mContext;
private ArrayList<EventsStrip.Item> mItems;
public EventsRecylerAdapter(Context context, ArrayList<EventsStrip.Item> items) {
mContext = context;
mItems = items;
}
#Override
public EventsRecylerAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
EventRowView v = new EventRowView(mContext);
ViewHolder vh = new ViewHolder(v);
return vh;
}
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
EventsStrip.Item item = mItems.get(position);
holder.mEventRowView.initItem(item);
}
#Override
public int getItemCount() {
return mItems.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder {
// each data item is just a string in this case
public EventRowView mEventRowView;
public int getMeasuredHeight() {
mEventRowView.measure(0, 0);
return mEventRowView.getMeasuredHeight();
}
public ViewHolder(EventRowView v) {
super(v);
mEventRowView = v;
}
}
}
Here is the code in my "EventsView" container that has the
protected void init(Context context) {
setOrientation(LinearLayout.VERTICAL);
ViewGroup.LayoutParams params = (ViewGroup.LayoutParams) getLayoutParams();
if (null == params)
params = generateDefaultLayoutParams();
params.height = ViewGroup.LayoutParams.WRAP_CONTENT;
params.width = ViewGroup.LayoutParams.WRAP_CONTENT;
setLayoutParams(params);
mHeaderScrollView = (HorizontalScrollView) findViewById(R.id.headerScrollView);
mHeaderScrollView.getViewTreeObserver().addOnScrollChangedListener(new HeaderScrollViewListener());
mRecyclerView = (RecyclerView) findViewById(R.id.EventsRecylerView);
mRecyclerView.addOnScrollListener(new RecyclerScrollListener());
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(mActivity);
mRecyclerView.setLayoutManager(mLayoutManager);
}
Since each row each wider than the device I would like to enable a horizontal scrollbar so I can scroll sideways to see more data in each row. Currently I am seeing all the data that I would expect to see just clipped at the edge of the screen.
Also, I would like to scroll horizontally programatically. When I call scrollTo(newxvalue, recylerview.getScrollY()) nothing happens. I don't want to scroll to a new position in the adapter list. I want to see more data that is currently "off screen" on the items currently on the screen. I have a static header at the top of the "list" with a horizontal scroll view on it. As the user drags the header I want the list below to stay in sync.
Any help/guidance would be appreciated

This turned out to be a lot simpler than I thought.
In a list view you will get unpredictable results if you put a list view inside a ScrollView . However in the case I simply put the header view and the RecylerView with a vertical linear layout manager inside of a horizontal ScrollView and it seems to behave as intended (i.e. RecylerView does not have the same limitations as ListView).
<HorizontalScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/headerScrollView"
>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="36dp"
android:background="#color/navigation_bar_color"
android:id="#+id/eventRowLayout"
android:paddingTop="5dp"
android:paddingBottom="5dp"
android:paddingLeft="2dp"
android:layout_alignParentTop="true" />
<android.support.v7.widget.RecyclerView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/EventsRecylerView"
android:layout_below="#+id/eventRowLayout">
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
</HorizontalScrollView>

Margin/padding in last Child in RecyclerView

I'm trying to add Padding/Margin Bottom in the last row and Padding/Margin Top in the first row. I can not do it in the item xml as it would affect all of my Children.
I have headers and children in my RecyclerView Adapter so I can not use the
android:padding="4dp"
android:clipToPadding="false"
I need to use it individually on the last first row of each header

This issue is even easier to solve. You can apply necessary padding to the RecylerView itself and set clipToPadding to false, otherwise, the padding will chop off your scrolling area. Here is an example
<android.support.v7.widget.RecyclerView
android:padding="4dp"
android:clipToPadding="false"
android:layout_width="match_parent"
android:layout_height="match_parent" />
See the padding will add 4dp on all sides including top and bottom. Then the clipToPadding parameter makes sure your child items are not chopped off. Now, add 4dp padding to all sides for your child items, and you are good to go. In total you get 8dp padding on sides and between items.

Instead of adding padding to both the top and bottom items, You can just add the padding to the top and bottom of your RecyclerView and set the clipToPadding attribute to false.
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false"
android:paddingTop="8dp"
android:paddingBottom="8dp" />

<android.support.v7.widget.RecyclerView
android:id="#+id/rv_tpf"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clipToPadding="false"
android:paddingBottom="100dp" />
Add android:clipToPadding="false" and android:paddingBottom="100dp" in your recyclerview.

use ItemDecoration:
private class SpacesItemDecoration extends RecyclerView.ItemDecoration {
private int space;
public SpacesItemDecoration(int space) {
this.space = space;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
int position = parent.getChildAdapterPosition(view);
boolean isLast = position == state.getItemCount()-1;
if(isLast){
outRect.bottom = space;
outRect.top = 0; //don't forget about recycling...
}
if(position == 0){
outRect.top = space;
// don't recycle bottom if first item is also last
// should keep bottom padding set above
if(!isLast)
outRect.bottom = 0;
}
}
}
and
//8dp as px
int space = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 8,
getResources().getDisplayMetrics()); // calculated
//int space = getResources().getDimensionPixelSize(
// R.dimen.list_item_padding_vertical); // from resources
recyclerView.addItemDecoration(new SpacesItemDecoration(space));

Add android:clipToPadding="false" and android:paddingBottom="65dp" in your recyclerview. If you are using fab menu button and actions on recycler view cell.
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/dinner_recycler_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clipToPadding="false"
android:paddingBottom="65dp"/>

I use this in kotlin to give bottom margin to last item only
override fun onBindViewHolder(holder: RecyclerView.ViewHolder(view), position: Int) {
if (position == itemsList.lastIndex){
val params = holder.itemView.layoutParams as FrameLayout.LayoutParams
params.bottomMargin = 100
holder.itemView.layoutParams = params
}else{
val params = holder.itemView.layoutParams as RecyclerView.LayoutParams
params.bottomMargin = 0
holder.itemView.layoutParams = params
}
//other codes ...
}

For some reason the old clipToPadding=false solution isn't working for me. So I added an ItemDecoration
https://gist.github.com/kassim/582888fa5960791264fc92bc41fb6bcf
public class BottomPaddingDecoration extends RecyclerView.ItemDecoration {
private final int bottomPadding;
public BottomPaddingDecoration(int bottomPadding) {
this.bottomPadding = bottomPadding;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
int position = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();
if (position == parent.getAdapter().getItemCount() - 1) {
outRect.set(0, 0, 0, bottomPadding);
}
}
}

Java equivalent to #Radesh answer:
#Override
public void onBindViewHolder(#NonNull RecyclerView.ViewHolder holder, int position) {
if (position == itemsList.size() - 1) {
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) holder.itemView.getLayoutParams();
params.bottomMargin = 100;
holder.itemView.setLayoutParams(params);
} else {
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) holder.itemView.getLayoutParams();
params.bottomMargin = 0;
holder.itemView.setLayoutParams(params);
}
}

I have modified amazing answer #snachmsm answer for better and give you idea how to use
properly
public class SpacesItemDecoration extends DividerItemDecoration {
private int space;
public SpacesItemDecoration(Context clContext,int oriantation,int space) {
super(clContext,oriantation);
this.space = space;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect,view,parent,state);
int position = parent.getChildAdapterPosition(view);
boolean isLast = position == state.getItemCount()-1;
if(isLast){
outRect.bottom = space;
outRect.top = 0; //don't forget about recycling...
}
/* if(position == 0){
outRect.top = space;
// don't recycle bottom if first item is also last
// should keep bottom padding set above
if(!isLast)
outRect.bottom = 0;
}*/
}
}

Long story short :
int freeSpaceAtBottom = 100; // the bottom free space in pixels
myRecyclerView.setClipToPadding(false);
myRecyclerView.setPadding(0,0,0,freeSpaceAtBottom);
setClipToPadding Sets whether this list view will clip its children to its padding and resize (but not clip) any EdgeEffect to the padded region, if padding is present. (1)

Hiding views in RecyclerView

I have code like this
public static class MyViewHolder extends RecyclerView.ViewHolder {
#InjectView(R.id.text)
TextView label;
public MyViewHolder(View itemView) {
super(itemView);
ButterKnife.inject(this, itemView);
}
public void hide(boolean hide) {
label.setVisibility(hide ? View.GONE : View.VISIBLE);
}
}
which maps to a single row in a RecyclerView. R.id.text is in fact the root view of the layout that gets inflated and passed in to the constructor here.
I'm using the default implementation of LinearLayoutManager.
In bindViewHolder, I call hide(true) on an instance of MyViewHolder, but instead of collapsing the row as expected, the row becomes invisible, maintaining its height and position in the RecyclerView. Has anyone else run into this issue?
How do you hide items in a RecyclerView?

There is no built in way to hide a child in RV but of course if its height becomes 0, it won't be visible :). I assume your root layout does have some min height (or exact height) that makes it still take space even though it is GONE.
Also, if you want to remove a view, remove it from the adapter, don't hide it. Is there a reason why you want to hide instead of remove ?

Put method setVisibility(boolean isVisible) in ViewHolder.
You can change itemView params(width and height) for LayoutManager:
public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
...
public void setVisibility(boolean isVisible){
RecyclerView.LayoutParams param = (RecyclerView.LayoutParams)itemView.getLayoutParams();
if (isVisible){
param.height = LinearLayout.LayoutParams.WRAP_CONTENT;
param.width = LinearLayout.LayoutParams.MATCH_PARENT;
itemView.setVisibility(View.VISIBLE);
}else{
itemView.setVisibility(View.GONE);
param.height = 0;
param.width = 0;
}
itemView.setLayoutParams(param);
}
public ViewHolder(View itemView) {
super(itemView);
...
}
}
and change visibility for ItemDecoration (Divider):
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
...
#Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
...
for (int i = 0; i < parent.getChildCount(); i++) {
if (parent.getChildAt(i).getVisibility() == View.GONE)
continue;
/* draw dividers */
}
}
}

You CAN do it!
First, you need to detect which position of item that you want to hide. You can custom getItemViewType to do it.
Next, on onCreateViewHolder, depend on the view type. You can do something like this:
if(viewType == TYPE_HIDE) {
v = LayoutInflater.from(parent.getContext()).inflate(R.layout.empty_item, parent, false);
vHolder = new ViewHolder(context, v, viewType, this);
break;
}
return vHolder;
-> empty item is a layout that have nothing, (in other word, it is default layout whenever created). or code:
<?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">
</LinearLayout>
Hope it help!

Okay, so the way I did it in the end was I had my whole dataset, say, myObjects and I had scenarios where I would only want to show subsets of that dataset.
Since setting visibility of rows in RecyclerView doesn't cause the heights to collapse, and setting the heights of the rows did not appear to do anything either, what I had to do was just keep a secondary dataset called myObjectsShown which was nothing more than a List<Integer> that would index into myObjects to determine which objects would be displayed.
I would then intermittently update myObjectsShown to contain the correct indices.
Therefore,
public int getItemCount() {
return myObjectsShown.size();
}
and
public void onBindViewHolder(MyViewHolder holder, int position) {
Object myObject = myObjects.get(myObjectsShown.get(position));
// bind object to viewholder here...
}

For hiding view in RecyclerView I hide/show view in OnBindViewHolder:
if (item.isShown) {
vh.FooterLayout.setVisibility(View.Visible);
} else {
vh.FooterLayout.setVisibility(View.Gone);
}
And for example - from activity I simply redraw needed item:
_postListAdapter.notifyItemChanged(position)// if you want show/hide footer - position is amountOfPosts.size() and also change bool variable - amountOfPosts[amountOfPosts.size()].isShown

For the sake of completeness, you should note that setting view visibility to GONE would not hide the margins. You need to do something like this :
if(itemView.getVisibility() != GONE) itemView.setVisibility(GONE);
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) itemView.getLayoutParams();
layoutParams.setMargins(0, 0, 0, 0);
itemView.setLayoutParams(layoutParams);