Develop Reference

Calling a function in Viewholder when item selected using SnapHelper

I have a horizontal Recycler view implemented with SnapHelper to get a carousal effect. In my ViewHolder I have a function to animate the views inside Recycler item. So whenever an item is scrolled to center (selected) in SnapHelper I need to start the animation. I have tried following code but its not working. Sometimes I am getting viewholder as null.
widgetScrollView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(final RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_SETTLING) {
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
int pos = ((LinearLayoutManager) widgetScrollView.getLayoutManager()).findFirstCompletelyVisibleItemPosition();
ResultTallyAdapter.ViewHolder viewHolder = (ResultTallyAdapter.ViewHolder) recyclerView.findViewHolderForAdapterPosition(pos);
viewHolder.startAnimation(MainActivity.this, pos);
}
}, 1000);
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
}
});

I was trying same thing like you. But code is different. I use SnapHelper to find current view and get position from this view and start operation on adapter by this position. You can get idea following code, may help you
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
synchronized (this) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
//calculatePositionAndScroll(recyclerView);
View view = snapHelper.findSnapView(recyclerView.getLayoutManager());
if (view != null) {
int pos = recyclerView.getLayoutManager().getPosition(view);
Log.d("RecyclerViewTest", "position: " + pos + " item: " + itemList.get(pos).getName());
makeSelectedItem(pos); // do your stuff on this view
// adapter.notifyDataSetChanged();
}
}
}
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
}
});

Recyclerview indicates that reaches the last item

I have a recycleView that I need to observe when the last item is reached but I have notice the it always indicate that I reached the last item even if I haven't scrolled yet.
My code for setting up the recycler:
newsRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
newsRecyclerView.setFocusable(false);
newsRecyclerView.setNestedScrollingEnabled(false);
newsAdapter = new NewsAdapter(getContext(), newsDetails, categoryNumber);
newsRecyclerView.setAdapter(newsAdapter);
layoutManager = new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false);
My xml code is:
<android.support.v7.widget.RecyclerView
android:id="#+id/news_recycler_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="4dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/news_top_stories_title_text_view" />

This is my code that I put in my Util, and use anywhere.
Util.setRecyclerViewLastPositionListner(rv, linearLayoutManager , new UtilitiesV2.OnLastPositionReached() {
#Override
public void onReached() {
// last position reached
}
});
Put this in Util.
private boolean userScrolled = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;
public interface OnLastPositionReached {
void onReached();
}
public void setRecyclerViewLastPositionListner(RecyclerView rvBooksMockTest, final LinearLayoutManager mLayoutManager, final OnLastPositionReached onLastPositionReached) {
rvBooksMockTest.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
userScrolled = true;
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// Here get the child count, item count and visibleitems
// from layout manager
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
// Now check if userScrolled is true and also check if
// the item is end then update recycler view and set
// userScrolled to false
if (userScrolled && (visibleItemCount + pastVisiblesItems) == totalItemCount) {
userScrolled = false;
if (onLastPositionReached != null) onLastPositionReached.onReached();
}
}
});
}
Update
According to your requirement, here is NestedScrollView bottom reach listener.
nestedScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
#Override
public void onScrollChanged() {
if (nestedScrollView != null) {
if (nestedScrollView.getChildAt(0).getBottom() <= (nestedScrollView.getHeight() + nestedScrollView.getScrollY())) {
//scroll view is at bottom
} else {
//scroll view is not at bottom
}
}
}
});

Thanks to Khemraj who give the tip for solution
because I have a recyclerview inside NestedScrollView and coordinator layout as parent for them
I have solved my problem like this:
public Disposable observeNestedScroll(LoadMoreListener listener) {
return RxNestedScrollView.scrollChangeEvents(nestedScrollView)
.subscribe(
viewScrollChangeEvent -> {
NestedScrollView nestedScrollView =(NestedScrollView) viewScrollChangeEvent.view();
if(nestedScrollView.getChildAt(nestedScrollView.getChildCount() - 1) != null) {
if ((viewScrollChangeEvent.scrollY() >= (nestedScrollView.getChildAt(nestedScrollView.getChildCount() - 1).getMeasuredHeight() - nestedScrollView.getMeasuredHeight())) &&
viewScrollChangeEvent.scrollY() > viewScrollChangeEvent.oldScrollY()) {
listener.onLoadMore();
}
}
});
}

I've seen to many responses for this question and I stand that all of them don't give accurate behavior as an outcome. However if you follow this approach I'm positive you'll get the best behavior.
rvCategories is your RecyclerView
categoriesList is the list passed to your adapter
binding.rvCategories.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
val position = (recyclerView.layoutManager as LinearLayoutManager).findLastCompletelyVisibleItemPosition()
if (position + 1 == categoriesList.size) {
// END OF RECYCLERVIEW IS REACHED
} else {
// END OF RECYCLERVIEW IS NOT REACHED
}
}
})

RecyclerView get item when it leaves screen

How can I get object from recyclerview when it leaves screen while scrolling? For example I have note with id 11 how can I get this note id whenever it leaves screen?

One way you could do it:
Boolean upScrolling;
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
LinearLayoutManager mgr = (LinearLayoutManager) recyclerView.getLayoutManager();
int topPosition = mgr.findFirstVisibleItemPosition();
/// your code
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy < 0) {
upScrolling = true;
} else if (dy > 0) {
upScrolling = false;
}
}
});
After scrolling up, in the listener you get the 1st visible item. At the position your code you write the code to check if the 1st visible item is the one below the item you want. If this is the case then you get the time it went off the screen.
Edited to check if it scrolls up or down.

Recyclerview onscrolllistener not working when setNestedScrollingEnabled to false

I want to implement pagination with recyclerView, for this I add addOnScrollListener to the recyclerView but I am having trouble with RecyclerView.OnScrollListener not working when I set rvGridExplore.setNestedScrollingEnabled(false);
But when I remove rvGridExplore.setNestedScrollingEnabled(false); it is working fine,
I don't know how to handle this.
Here is code:
rvGridExplore = (RecyclerView) view.findViewById(R.id.rvGridExplore);
final GridLayoutManager glm = new GridLayoutManager(context,2);
// rvGridExplore.setNestedScrollingEnabled(false);
rvGridExplore.setLayoutManager(glm);
// final int visibleItemCount,totalCount,pastVisibleItems;
rvGridExplore.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
Log.v("scrollll","state changed");
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy > 0) {
int totalCount = glm.getItemCount();
int visibleItemCount = glm.getChildCount();
int pastVisibleItems = glm.findFirstVisibleItemPosition();
if (loading) {
if ((visibleItemCount + pastVisibleItems) >= totalCount) {
Log.v("scroll","scrolled"+pastVisibleItems);
}
}
}
}
});

Do add setOnScrollChangeListner to your NestedScrollView
nestedScrollview.setOnScrollChangeListener(new NestedScrollView.OnScrollChangeListener() {
#Override
public void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
if (scrollY == (v.getChildAt(0).getMeasuredHeight() - v.getMeasuredHeight())) {
if(loading)
onClick();
loading=false;
}
}
});
after loading data from server set boolean loading=true.

This question may be old, but to help others who stumbled upon this problem, i would like to share what i did. I had to implement onScroll Listener to recyclerview to load data from server and to make some UI changes. And also needed swipeRefresh Layout for refreshing data.
This was my xml file structure,
-RelativeLayout
-SwipeRefreshLayout
-NestedScrollView
-LinearLayout(Vertical)
-Multiple views required
After this, to detect up and down scrolling i implemented setOnScrollListener to the NestedScrollView.
Normal usage of SwipeRefreshLayout to refresh data.
And to load more data i implemented the logic inside onScrollListener of NestedScrollingView.
if (scrollY == (v.getChildAt(0).getMeasuredHeight() - v.getMeasuredHeight())) {
// Load More Data
}

If you are recyclerView is embedded in any of the NestedScrollView, then you are supposed to attach the onScrollListener to NestedScrollView.
This will work!
if (recyclerView.getLayoutManager() instanceof GridLayoutManager) {
final GridLayoutManager gridLayoutManager = (GridLayoutManager) recyclerView.getLayoutManager();
nestedScrollView.setOnScrollChangeListener(new NestedScrollView.OnScrollChangeListener() {
#Override
public void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
if (scrollY == (v.getChildAt(0).getMeasuredHeight() - v.getMeasuredHeight())) {
totalItemCount = gridLayoutManager.getItemCount();
lastVisibleItem = gridLayoutManager.findLastVisibleItemPosition();
if (!loading
&& totalItemCount <= (lastVisibleItem + visibleThreshold)) {
// End has been reached
// Do something
if (onLoadMoreListener != null) {
onLoadMoreListener.onLoadMore();
}
loading = true;
}
}
}
});
}

You said in a comment to your question "
it is under NestedScrollView which is under coordinator layout, if i remove this, Toolbar is not scrolling up". This is a mistake.
I have found that you cannot have it both ways, the CoordinatorLayout behaviour breaks when you have a RecyclerView inside a NestedScrollView to which you've added the behaviour. You need to use one or the other.
When you have a RecyclerView inside a NestedScrollView it will work as long as you set RecyclerView.setNestedScrollingEnabled(false), but as you found out this means that the OnScrollListener is not called.
The only way for all components to work correctly is to remove the NestedScrollView, make sure you do not set nesting scroll to false and work from there. Otherwise the RecyclerView.OnScrollListener events will not fire correctly.

Step 1 : Create EndlessRecyclerOnScrollListener
public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener {
public static String TAG = EndlessRecyclerOnScrollListener.class.getSimpleName();
// use your LayoutManager instead
private LinearLayoutManager llm;
public EndlessRecyclerOnScrollListener(LinearLayoutManager sglm) {
this.llm = llm;
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (!recyclerView.canScrollVertically(1)) {
onScrolledToEnd();
}
}
public abstract void onScrolledToEnd();
}
Step 2: Apply scroll listener to recycler view.
recyclerview.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager) {
#Override
public void onScrolledToEnd() {
Log.e("Position", "Last item reached");
if (loadMore == true) {
// put your Load more code
// add 10 by 10 to tempList then notify changing in data
}
}
});

remove the nested scroll view use linear or relative layout instead of it as root element then you can write recyclerview.setNestedScrollEnabled(false);

How to scroll horizontal RecyclerView programmatically?

I have a horizontal RecyclerView and two button (Next,Previous) as shown in the image below.
so i need to move to the next item or position by use these buttons , i know about method called scrollTo but i don't know how does it work

I found the answer:
case R.id.next:
mRecyclerView.getLayoutManager().scrollToPosition(linearLayoutManager.findLastVisibleItemPosition() + 1);
break;
case R.id.pre:
mRecyclerView.getLayoutManager().scrollToPosition(linearLayoutManager.findFirstVisibleItemPosition() - 1);
break;

RecyclerViews have a methods which they expose for scrolling to a certain position:
Snap scroll to a given position:
mRecyclerView.scrollToPosition(int position)
Smooth scroll to a given position:
mRecyclerView.smoothScrollToPosition(int position)
For these methods to work, the LayoutManager of the RecyclerView needs to have implemented these methods, and LinearLayoutManager does implement these in a basic manner, so you should be good to go.

case R.id.next:
mRecyclerView.getLayoutManager().scrollToPosition(linearLayoutManager.findLastVisibleItemPosition() + 1);
break;
case R.id.pre:
mRecyclerView.getLayoutManager().scrollToPosition(linearLayoutManager.findFirstVisibleItemPosition() - 1);
break;

int mFirst=0, mLast=0;
recyclerview.setOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
LinearLayoutManager llm = (LinearLayoutManager) recyclerview.getLayoutManager();
mLast = llm.findLastCompletelyVisibleItemPosition();
mFirst = llm.findFirstCompletelyVisibleItemPosition();
}
});
imgRight.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
LinearLayoutManager llm = (LinearLayoutManager) recyclerview.getLayoutManager();
llm.scrollToPositionWithOffset(mLast + 1, List.length());
}
});
imgLeft.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
LinearLayoutManager llm = (LinearLayoutManager) recyclerview.getLayoutManager();
llm.scrollToPositionWithOffset(mFirst - 1, List.length());
}
});

Adding to the accepted answer you need to have a check for the present position so that you don't get a nullPointerException like below
binding.imageViewleft.setOnClickListener {
if (layoutManager.findFirstCompletelyVisibleItemPosition()>0){
binding.recyclerView.layoutManager?.scrollToPosition(layoutManager.findFirstCompletelyVisibleItemPosition()-1)
}
}
binding.iv2.setOnClickListener {
if (layoutManager.findLastCompletelyVisibleItemPosition()<(sectiondata.size-1) ){
binding.recyclerView.layoutManager?.scrollToPosition(layoutManager.findLastCompletelyVisibleItemPosition()+1)
}
}