Develop Reference

How do I detect OverScroll in android RecyclerView?

I have tried to overwrite onOverScrolled() but it is not triggered:
public class MyRecyclerView extends RecyclerView {
public MyRecyclerView(#NonNull Context context) {
super(context);
}
public MyRecyclerView(#NonNull Context context, #Nullable AttributeSet attrs) {
super(context, attrs);
}
public MyRecyclerView(#NonNull Context context, #Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);
Toast.makeText(getContext(), "overScrolled", Toast.LENGTH_SHORT).show();
}
}
My RecyclerView has recyclerView.setOverScrollMode(View.OVER_SCROLL_ALWAYS);

Try this to find bottom overscroll and top overscroll
Find bottom overscroll and top overscroll Using LayoutManager
import android.os.Bundle;
import java.util.ArrayList;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
public class MainActivity extends AppCompatActivity {
RecyclerView myRecyclerView;
ArrayList<String> arrayList = new ArrayList<>();
DataAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myRecyclerView = findViewById(R.id.myRecyclerView);
LinearLayoutManager linearLayoutManager= new LinearLayoutManager(this){
#Override
public int scrollVerticallyBy ( int dx, RecyclerView.Recycler recycler, RecyclerView.State state ) {
int scrollRange = super.scrollVerticallyBy(dx, recycler, state);
int overScroll = dx - scrollRange;
if (overScroll > 0) {
Utils.printLog("NILU_PILU :-> BOTTOM OVERSCROLL");
} else if (overScroll < 0) {
Utils.printLog("NILU_PILU :-> TOP OVERSCROLL");
}
return scrollRange;
}
};
myRecyclerView.setLayoutManager(linearLayoutManager);
myRecyclerView.setHasFixedSize(true);
addDataToList();
adapter = new DataAdapter(this, arrayList);
myRecyclerView.setAdapter(adapter);
}
private void addDataToList() {
for (int i = 0; i < 50; i++) {
arrayList.add("NILU_PILU :-> " + i);
}
}
}
Find bottom overscroll Using RecyclerView.addOnScrollListener()
myRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy > 0) {
int pos = linearLayoutManager.findLastVisibleItemPosition();
int numItems = myRecyclerView.getAdapter().getItemCount();
if (pos >= numItems - 1 ) {
Utils.printLog("NILU_PILU :-> BOTTOM OVERSCROLL");
}
}
}
});

Here is a solution I found on reddit:
Instead of a custom recyclerview, you create a custom LinearLayoutManager and just overwrite your layout managers scrollVerticallyBy() method and check if dx/dy minus the value returned by the super implementation is != 0. Then overscroll has occured.
#Override
public int scrollVerticallyBy ( int dx, RecyclerView.Recycler recycler,
RecyclerView.State state ) {
int scrollRange = super.scrollVerticallyBy(dx, recycler, state);
int overscroll = dx - scrollRange;
if (overscroll > 0) {
// bottom overscroll
} else if (overscroll < 0) {
// top overscroll
}
return scrollRange;
}

RecyclerView inside NestedScrollView takes too much time when loading large amount of data

RecyclerView inside NestedScrollView freezes the Activity when loading large amount of data. It loads much faster with ScrollView, but scrolling is affected in that case.
I tried setting attributes like setAutoMeasure and setNestedScrollingEnabled which did not help.
Any suggestions?

Recycling of views is not supported inside NestedScrollViews as I understand, so the suggestion would be to try to change your layout.

This help to increase the speed of recycler view scrolling.
SpeedyLinearLayoutManager linearLayoutManager = new SpeedyLinearLayoutManager(MainActivity.this);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
myRecyclerView.setLayoutManager(linearLayoutManager);
SpeedyLinearLayoutManager.class
public class SpeedyLinearLayoutManager extends LinearLayoutManager {
private static final float MILLISECONDS_PER_INCH = 2f; //default is 25f (bigger = slower)
public SpeedyLinearLayoutManager(Context context) {
super(context);
}
public SpeedyLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
public SpeedyLinearLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
#Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
final LinearSmoothScroller linearSmoothScroller = new LinearSmoothScroller(recyclerView.getContext()) {
#Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return SpeedyLinearLayoutManager.this.computeScrollVectorForPosition(targetPosition);
}
#Override
protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH / displayMetrics.densityDpi;
}
};
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}
}

Use Custom list view instead of Recycler view inside scroll view...
Check this Answer
Custom List View
import android.content.Context;
import android.util.AttributeSet;
import android.view.ViewGroup;
import android.widget.ListView;
public class ExpandableHeightListView extends ListView {
boolean expanded = true;
public ExpandableHeightListView(Context context) {
super(context);
}
public ExpandableHeightListView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ExpandableHeightListView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
}
public boolean isExpanded() {
return expanded;
}
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// HACK! TAKE THAT ANDROID!
if (isExpanded()) {
// Calculate entire height by providing a very large height hint.
// View.MEASURED_SIZE_MASK represents the largest height possible.
int expandSpec = MeasureSpec.makeMeasureSpec(MEASURED_SIZE_MASK,
MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, expandSpec);
ViewGroup.LayoutParams params = getLayoutParams();
params.height = getMeasuredHeight();
} else {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
public void setExpanded(boolean expanded) {
this.expanded = expanded;
}
}

you can include app:layout_behavior="#string/appbar_scrolling_view_behavior"
<android.support.v7.widget.RecyclerView
android:id="#+id/recyclerView"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
or disable the nested scrolling behavior for the recycler view.
recyclerView.setNestedScrollingEnabled(false);

DividerItemDecoration is not applied when RecyclerView.Adapter.notifyItemInserted() is called

I created a custom divider for a RecyclerView by extending DividerItemDecoration and then applying it by calling addItemDecoration on my RecyclerView.
The RecyclerView displays everything nicely untill my data set changes and I call notifyItemInserted. New item is indeed inserted in the RecyclerView, but it is displayed without my custom divider (dividers for the other items are in place).
When I scroll away from the newly inserted item and then return back to it - it appears with the divider in place.
EDIT Code snippets:
mRecyclerView.addItemDecoration(new GapDividerItemDecoration(mContext, LinearLayoutManager.VERTICAL, 16));
My custom decorator (just adds space between RecyclerView items provided in dp):
public class GapDividerItemDecoration extends DividerItemDecoration {
private int mSpaceInPixels;
private int mOrientation;
public GapDividerItemDecoration(Context context, int orientation, float dp) {
super(context, orientation);
mSpaceInPixels = dpToPixels(dp);
mOrientation = orientation;
}
private int dpToPixels(float dp) {
return (int) (dp * (((float) Resources.getSystem().getDisplayMetrics().densityDpi) / DisplayMetrics.DENSITY_DEFAULT));
}
#Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
// Do not draw the divider
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
if (parent.getChildAdapterPosition(view) != parent.getAdapter().getItemCount() - 1) {
if (mOrientation == LinearLayout.VERTICAL) {
outRect.bottom = mSpaceInPixels;
} else {
outRect.right = mSpaceInPixels;
}
}
}
I do not provide the rest of the code, because it is pretty straight forward (besides, I know that it is working, and the issue might be with the RecyclerView itself or just my custom decorator).

This is a too late answer, but I will answer because I have the same problem. Try call RecyclerView.invalidateItemDecorations() before insert data.

Android LinearSnapHelper - how to increase scrolling/"snapping" speed?

I'm using a LinearSnapHelper to make items in my RecyclerView "snap" into place on the screen (my cards take up most of the screen, so I want them to snap into place and fill the screen on every swipe/fling/scroll).
I'm struggling with how to make the cards snap into place faster. I've tried creating a custom LinearLayoutManager (and editing the calculateSpeedPerPixel method in scrollToPosition or smoothScrollToPosition), as well as a custom RecyclerView (and editing the fling method). But nothing effects the speed that cards "snap" into place.
I suppose the issue is that I don't really understand how LinearSnapHelper "scrolls" the cards into position. It doesn't seem to use LinearLayoutManager's scrollToPosition or smoothScrollToPosition methods.
snapHelper = new LinearSnapHelper() {
#Override
public int findTargetSnapPosition(RecyclerView.LayoutManager layoutManager, int velocityX, int velocityY) {
View centerView = findSnapView(layoutManager);
if (centerView == null) {
return RecyclerView.NO_POSITION;
}
int position = layoutManager.getPosition(centerView);
int targetPosition = -1;
if (layoutManager.canScrollHorizontally()) {
if (velocityX < 0) {
targetPosition = position - 1;
} else {
targetPosition = position + 1;
}
}
if (layoutManager.canScrollVertically()) {
if (velocityY > 0) {
targetPosition = position + 1;
} else {
targetPosition = position - 1;
}
}
final int firstItem = 0;
final int lastItem = layoutManager.getItemCount() - 1;
targetPosition = Math.min(lastItem, Math.max(targetPosition, firstItem));
return targetPosition;
}
};
snapHelper.attachToRecyclerView(mRecyclerView);

As 郭玉龙 mentioned, SnapHelper call RecyclerView.smoothScrollBy() method. And it use default sQuinticInterpolator.
To change speed of snap you can do next:
public class SlowdownRecyclerView extends RecyclerView {
// Change pow to control speed.
// Bigger = faster. RecyclerView default is 5.
private static final int POW = 2;
private Interpolator interpolator;
public SlowdownRecyclerView(Context context) {
super(context);
createInterpolator();
}
public SlowdownRecyclerView(Context context, #Nullable AttributeSet attrs) {
super(context, attrs);
createInterpolator();
}
public SlowdownRecyclerView(Context context, #Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
createInterpolator();
}
private void createInterpolator(){
interpolator = new Interpolator() {
#Override
public float getInterpolation(float t) {
t = Math.abs(t - 1.0f);
return (float) (1.0f - Math.pow(t, POW));
}
};
}
#Override
public void smoothScrollBy(int dx, int dy) {
super.smoothScrollBy(dx, dy, interpolator);
}
Or you can implement your own interpolator.

The speed of snapping scroll is affected by RecyclerView.smoothScrollBy().
Here's the snippet of source code.
Override this function to increase or decrease the speed of snapping scroll.

I wound up doing this by adding a ScrollListener to my RecycleView, and then creating a custom LinearLayoutManager and custom smoothScrollToPosition method.
final CustomLinearLayoutManager mLayoutManager = new CustomLinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
private boolean scrollingUp;
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
scrollingUp = dy < 0;
}
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
int visiblePosition = scrollingUp ? mLayoutManager.findFirstVisibleItemPosition() : mLayoutManager.findLastVisibleItemPosition();
int completelyVisiblePosition = scrollingUp ? mLayoutManager
.findFirstCompletelyVisibleItemPosition() : mLayoutManager
.findLastCompletelyVisibleItemPosition();
if (visiblePosition != completelyVisiblePosition) {
recyclerView.smoothScrollToPosition(visiblePosition);
return;
}
}
});

I achieved this using a library https://github.com/rubensousa/GravitySnapHelper
you can also override findTargetSnapPosition to get pager like scroll
tweek the scrollMsPerInch to increase / decrease speed
val snapHelper : GravitySnapHelper = GravitySnapHelper(Gravity.CENTER)
// the lower the higher the speed, default is 100f
snapHelper.scrollMsPerInch = 40f
snapHelper.attachToRecyclerView(binding?.mRecyclerView)

Actually you can modify the LinearSnapHelper and SnapHelperClass by simply copy/paste the existing code the only thing you will do is to set MILLISECONDS_PER_INCH on SnapHelper as you want and then use simply use the LinearSnapHelper you created

Add space to the end of the RecyclerView

I have a recyclerview with a gridlayout. What I want is when the user scrolls to the end of the list (see my bad mockup), there should be an empty space with a height of 50dp, which isn't the same dimensions as my grid.
Note that this space is only visible at the very end end, as I do not want to change the layout. I could make it so that the recycerview has a margin bottom of 50dp, but I do not want to do that.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:fab="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:scrollbars="vertical"
/>
</RelativeLayout>

<RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="50dp"
android:clipToPadding="false"
/>

This is best achieved with an item decoration.
Here's an example that works with a LinearLayoutManager - you'll have to adjust to suit for your Grid layout. What it does is checks each item to see if it's the last one, and if it is it adds the offset to the bottom of it. For a Grid layout, the hard part is figuring out whether your item position is in the last row or not.
// After setting layout manager, adapter, etc...
float offsetPx = getResources().getDimension(R.dimen.bottom_offset_dp);
BottomOffsetDecoration bottomOffsetDecoration = new BottomOffsetDecoration((int) offsetPx);
mRecyclerView.addItemDecoration(bottomOffsetDecoration);
...
static class BottomOffsetDecoration extends RecyclerView.ItemDecoration {
private int mBottomOffset;
public BottomOffsetDecoration(int bottomOffset) {
mBottomOffset = bottomOffset;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
int dataSize = state.getItemCount();
int position = parent.getChildAdapterPosition(view);
if (dataSize > 0 && position == dataSize - 1) {
outRect.set(0, 0, 0, mBottomOffset);
} else {
outRect.set(0, 0, 0, 0);
}
}
}
For a GridLayoutManager, inside the getItemOffsets method you could do something similar to this to figure out if it's the last row:
GridLayoutManager grid = (GridLayoutManager)parent.getLayoutManager();
if ((dataSize - position) <= grid.getSpanCount()) {
outRect.set(0, 0, 0, mBottomOffset);
} else {
outRect.set(0, 0, 0, 0);
}

I had the similar issue. After reading all others replies and I found the changes in layout xml for recyclerview worked for my recycler view as expected:
android:paddingBottom="127dp"
android:clipToPadding="false"
android:scrollbarStyle="outsideOverlay"
The complete layout looks like:
<android.support.v7.widget.RecyclerView
android:id="#+id/library_list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="160dp"
android:layout_marginEnd="160dp"
tools:listitem="#layout/library_list_item" />
For the effect of before and after see the link at androidblog.us:
Adding Space to End of Android Recylerview
Let me know how it works for you.
David

You can try the below code, remember "I do not test this code"
public class MyRecyclerView extends RecyclerView {
private Context context;
public MyRecyclerView(Context context) {
super(context);
this.context = context;
}
public MyRecyclerView(Context context, AttributeSet attrs) {
super(context, attrs);
this.context = context;
}
public MyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.context = context;
}
#Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
View view = (View) getChildAt(getChildCount()-1);
int diff = (view.getBottom()-(getHeight()+getScrollY()+view.getTop()));
if( diff == 0 ){ // if diff is zero, then the bottom has been reached
TextView tv = new TextView(context);
tv.setHeight(dpToPx(50));
addView(tv,getChildCount());//update --> add to last
requestLayout();
}
super.onScrollChanged(l, t, oldl, oldt);
}
public int dpToPx(int dp) {
DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
int px = Math.round(dp * (displayMetrics.xdpi / DisplayMetrics.DENSITY_DEFAULT));
return px;
}
}
and in layout:
<your_packagae.MyRecyclerView
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"
/>

Make a class name with BottomOffsetDecoration
public class BottomOffsetDecoration extends RecyclerView.ItemDecoration {
private int mBottomOffset;
public BottomOffsetDecoration(int bottomOffset) {
mBottomOffset = bottomOffset;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
int dataSize = state.getItemCount();
int position = parent.getChildAdapterPosition(view);
if (dataSize > 0 && position == dataSize - 1) {
outRect.set(0, 0, 0, mBottomOffset);
} else {
outRect.set(0, 0, 0, 0);
}
}
}
then Add these line after adding adapter and layoutmanager to recyclerview
float offsetPx = getResources().getDimension(R.dimen.bottom_offset_dp);
BottomOffsetDecoration bottomOffsetDecoration = new BottomOffsetDecoration((int) offsetPx);
rv.addItemDecoration(bottomOffsetDecoration);
and for GridLayout Add these lines after assigning recyclerview layout manager
GridLayoutManager grid = (GridLayoutManager)parent.getLayoutManager();
if ((dataSize - position) <= grid.getSpanCount()) {
outRect.set(0, 0, 0, mBottomOffset);
} else {
outRect.set(0, 0, 0, 0);
}