Related
I need to know which elements are currently displayed in my RecyclerView. There is no equivalent to the OnScrollListener.onScroll(...) method on ListViews. I tried to work with View.getGlobalVisibleRect(...), but that hack is too ugly and does not always work too.
Someone any ideas?
First / last visible child depends on the LayoutManager.
If you are using LinearLayoutManager or GridLayoutManager, you can use
int findFirstVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
For example:
GridLayoutManager layoutManager = ((GridLayoutManager)mRecyclerView.getLayoutManager());
int firstVisiblePosition = layoutManager.findFirstVisibleItemPosition();
For LinearLayoutManager, first/last depends on the adapter ordering. Don't query children from RecyclerView; LayoutManager may prefer to layout more items than visible for caching.
For those who have a logic to be implemented inside the RecyclerView adapter, you can still use the #ernesto approach combined with an on scrollListener to get what you want as the RecyclerView is consulted.
Inside the adapter you will have something like this:
#Override
public void onAttachedToRecyclerView(#NonNull RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
if(manager instanceof LinearLayoutManager && getItemCount() > 0) {
LinearLayoutManager llm = (LinearLayoutManager) manager;
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int visiblePosition = llm.findFirstCompletelyVisibleItemPosition();
if(visiblePosition > -1) {
View v = llm.findViewByPosition(visiblePosition);
//do something
v.setBackgroundColor(Color.parseColor("#777777"));
}
}
});
}
}
Finally, I found a solution to know if the current item is visible, from the onBindViewHolder event in the adapter.
The key is the method isViewPartiallyVisible from LayoutManager.
In your adapter, you can get the LayoutManager from the RecyclerView, which you get as parameter from the onAttachedToRecyclerView event.
You can use recyclerView.getChildAt() to get each visible child, and setting some tag convertview.setTag(index) on these view in adapter code will help you to relate it with adapter data.
Addendum:
The proposed functions findLast...Position() do not work correctly in a scenario with a collapsing toolbar while the toolbar is expanded.
It seems that the recycler view has a fixed height, and while the toolbar is expanded, the recycler is moved down, partially out of the screen. As a consequence the results of the proposed functions are too high. Example: The last visible item is told to be #9, but in fact item #7 is the last one that is on screen.
This behaviour is also the reason why my view often failed to scroll to the correct position, i.e. scrollToPosition() did not work correctly (I finally collapsed the toolbar programmatically).
Every answer above is correct and I would like to add also a snapshot from my working codes.
recycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
// Some code when initially scrollState changes
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// Some code while the list is scrolling
LinearLayoutManager lManager = (LinearLayoutManager) recyclerView.getLayoutManager();
int firstElementPosition = lManager.findFirstVisibleItemPosition();
}
});
Following Linear / Grid LayoutManager methods can be used to check which items are visible.
int findFirstVisibleItemPosition();
int findLastVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
and if you want to track is item visible on screen for some threshold then you can refer to the following blog.
https://proandroiddev.com/detecting-list-items-perceived-by-user-8f164dfb1d05
For StaggeredGridLayoutManager do this:
RecyclerView rv = findViewById(...);
StaggeredGridLayoutManager lm = new StaggeredGridLayoutManager(...);
rv.setLayoutManager(lm);
And to get visible item views:
int[] viewsIds = lm.findFirstCompletelyVisibleItemPositions(null);
ViewHolder firstViewHolder = rvPlantios.findViewHolderForLayoutPosition(viewsIds[0]);
View itemView = viewHolder.itemView;
Remember to check if it is empty.
You can find the first and last visible children of the recycle view and check if the view you're looking for is in the range:
var visibleChild: View = rv.getChildAt(0)
val firstChild: Int = rv.getChildAdapterPosition(visibleChild)
visibleChild = rv.getChildAt(rv.childCount - 1)
val lastChild: Int = rv.getChildAdapterPosition(visibleChild)
println("first visible child is: $firstChild")
println("last visible child is: $lastChild")
For those who are looking for an answer in Kotlin:
fun getVisibleItem(recyclerView : RecyclerView) {
recyclerView.addOnScrollListener(object: RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if(newState == RecyclerView.SCROLL_STATE_IDLE) {
val index = (recyclerView.layoutManager.findFirstVisibleItemPosition
//use this index for any operation you want to perform on the item visible on screen. eg. log(arrayList[index])
}
}
})
}
You can explore other methods for getting the position as per your use case.
int findFirstCompletelyVisibleItemPosition()
int findLastVisibleItemPosition()
int findLastCompletelyVisibleItemPosition()
if the visible item position is different from the item position toast message will show on the screen.
myRecyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
LinearLayoutManager manager= (LinearLayoutManager) myRecyclerview.getLayoutManager();
assert manager != null;
int visiblePosition = manager.findLastCompletelyVisibleItemPosition();
if(visiblePosition > -1&&a!=visiblePosition) {
Toast.makeText(context,String.valueOf(visiblePosition),Toast.LENGTH_SHORT).show();
//do something
a=visiblePosition;
}
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
//Some code while the list is scrolling
}
});
I have created a activity Webview content placed in Recyclerview.
I want to get the scroll Y position when I scroll webview.
I tried Webview.getScrollY(), Webview.getY(), RecyclerView.getScrollY(), RecyclerView.getY(),... but it do not work fine. I can't get current scroll Y.
Is there any suggest for get scroll Y of Webview or RecyclerView ?
Use a RecyclerView.OnScrollListener for the RecyclerView and a View.OnScrollChangeListener for the webview.
You'll have to keep track of the total scroll yourself, like this:
private int mTotalScrolled = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
mTotalScrolled += dy;
}
});
...
}
private int getScrollForRecycler(){
return mTotalScrolled;
}
computeVerticalScrollOffset()is more convenient at this situation as #Pkmmte mentioned.
mTotalScrolled = recyclerView.computeVerticalScrollOffset();
Iphone App video link
How I can design and develop view which is posted in above video? This is basically the item expansion of recyclerview with animation. I have tried with onItemtouchlistener of recyclerview and also with some custom view with animation, but didn't get the accurate result.
Finally i came accross addonscrolllistener, this give me results but not accurate.
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
if(newState == RecyclerView.FOCUS_UP) {
System.out.println("hello, ia m going up");
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy > 0){
TextView tv = (TextView)recyclerView.findViewById(R.id.title);
//tv.setVisibility(View.VISIBLE);
if (tv.getVisibility()==View.VISIBLE){
System.out.println("yes");
}else {
slideToTop(tv);
}
}
}
});
private void slideToTop(View view){
TranslateAnimation animate = new TranslateAnimation(0,0,0,-view.getHeight());
animate.setDuration(1000);
animate.setFillAfter(false);
view.startAnimation(animate);
view.setVisibility(View.VISIBLE);
}
I think your question is too broad - however, here is some psuedocode:
onScrolled() {
View child = getSecondVisibleChild();
int distanceFromTop = child.getTop();
int distanceAtWhichExpandingShouldOccur = 100;
if(distanceFromTop < distanceAtWhichExpandingShouldOccur ) {
child.setHeight(child.getOriginalHeight() + (distanceFromTop - distanceAtWhichExpandingShouldOccur))
}
}
So you'll notice, the second visible child is the one who's height changes. It changed when it's less than distanceAtWhichExpandingShouldOccur from the top of the window. Its height changes to ensure its bottom remains stationary - therefore its height is increasing at the same pace its top is moving.
Once it's no longer the second visible child (aka, its top is 0), it should be scrolled off as normal and the next child should have its height changed when its top is less than distanceAtWhichExpandingShouldOccur.
This library can be a study case for you: https://github.com/florent37/MaterialLeanBack
I need to know which elements are currently displayed in my RecyclerView. There is no equivalent to the OnScrollListener.onScroll(...) method on ListViews. I tried to work with View.getGlobalVisibleRect(...), but that hack is too ugly and does not always work too.
Someone any ideas?
First / last visible child depends on the LayoutManager.
If you are using LinearLayoutManager or GridLayoutManager, you can use
int findFirstVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
For example:
GridLayoutManager layoutManager = ((GridLayoutManager)mRecyclerView.getLayoutManager());
int firstVisiblePosition = layoutManager.findFirstVisibleItemPosition();
For LinearLayoutManager, first/last depends on the adapter ordering. Don't query children from RecyclerView; LayoutManager may prefer to layout more items than visible for caching.
For those who have a logic to be implemented inside the RecyclerView adapter, you can still use the #ernesto approach combined with an on scrollListener to get what you want as the RecyclerView is consulted.
Inside the adapter you will have something like this:
#Override
public void onAttachedToRecyclerView(#NonNull RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
if(manager instanceof LinearLayoutManager && getItemCount() > 0) {
LinearLayoutManager llm = (LinearLayoutManager) manager;
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int visiblePosition = llm.findFirstCompletelyVisibleItemPosition();
if(visiblePosition > -1) {
View v = llm.findViewByPosition(visiblePosition);
//do something
v.setBackgroundColor(Color.parseColor("#777777"));
}
}
});
}
}
Finally, I found a solution to know if the current item is visible, from the onBindViewHolder event in the adapter.
The key is the method isViewPartiallyVisible from LayoutManager.
In your adapter, you can get the LayoutManager from the RecyclerView, which you get as parameter from the onAttachedToRecyclerView event.
You can use recyclerView.getChildAt() to get each visible child, and setting some tag convertview.setTag(index) on these view in adapter code will help you to relate it with adapter data.
Addendum:
The proposed functions findLast...Position() do not work correctly in a scenario with a collapsing toolbar while the toolbar is expanded.
It seems that the recycler view has a fixed height, and while the toolbar is expanded, the recycler is moved down, partially out of the screen. As a consequence the results of the proposed functions are too high. Example: The last visible item is told to be #9, but in fact item #7 is the last one that is on screen.
This behaviour is also the reason why my view often failed to scroll to the correct position, i.e. scrollToPosition() did not work correctly (I finally collapsed the toolbar programmatically).
Every answer above is correct and I would like to add also a snapshot from my working codes.
recycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
// Some code when initially scrollState changes
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// Some code while the list is scrolling
LinearLayoutManager lManager = (LinearLayoutManager) recyclerView.getLayoutManager();
int firstElementPosition = lManager.findFirstVisibleItemPosition();
}
});
Following Linear / Grid LayoutManager methods can be used to check which items are visible.
int findFirstVisibleItemPosition();
int findLastVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
and if you want to track is item visible on screen for some threshold then you can refer to the following blog.
https://proandroiddev.com/detecting-list-items-perceived-by-user-8f164dfb1d05
For StaggeredGridLayoutManager do this:
RecyclerView rv = findViewById(...);
StaggeredGridLayoutManager lm = new StaggeredGridLayoutManager(...);
rv.setLayoutManager(lm);
And to get visible item views:
int[] viewsIds = lm.findFirstCompletelyVisibleItemPositions(null);
ViewHolder firstViewHolder = rvPlantios.findViewHolderForLayoutPosition(viewsIds[0]);
View itemView = viewHolder.itemView;
Remember to check if it is empty.
You can find the first and last visible children of the recycle view and check if the view you're looking for is in the range:
var visibleChild: View = rv.getChildAt(0)
val firstChild: Int = rv.getChildAdapterPosition(visibleChild)
visibleChild = rv.getChildAt(rv.childCount - 1)
val lastChild: Int = rv.getChildAdapterPosition(visibleChild)
println("first visible child is: $firstChild")
println("last visible child is: $lastChild")
For those who are looking for an answer in Kotlin:
fun getVisibleItem(recyclerView : RecyclerView) {
recyclerView.addOnScrollListener(object: RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if(newState == RecyclerView.SCROLL_STATE_IDLE) {
val index = (recyclerView.layoutManager.findFirstVisibleItemPosition
//use this index for any operation you want to perform on the item visible on screen. eg. log(arrayList[index])
}
}
})
}
You can explore other methods for getting the position as per your use case.
int findFirstCompletelyVisibleItemPosition()
int findLastVisibleItemPosition()
int findLastCompletelyVisibleItemPosition()
if the visible item position is different from the item position toast message will show on the screen.
myRecyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
LinearLayoutManager manager= (LinearLayoutManager) myRecyclerview.getLayoutManager();
assert manager != null;
int visiblePosition = manager.findLastCompletelyVisibleItemPosition();
if(visiblePosition > -1&&a!=visiblePosition) {
Toast.makeText(context,String.valueOf(visiblePosition),Toast.LENGTH_SHORT).show();
//do something
a=visiblePosition;
}
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
//Some code while the list is scrolling
}
});
I need to know which elements are currently displayed in my RecyclerView. There is no equivalent to the OnScrollListener.onScroll(...) method on ListViews. I tried to work with View.getGlobalVisibleRect(...), but that hack is too ugly and does not always work too.
Someone any ideas?
First / last visible child depends on the LayoutManager.
If you are using LinearLayoutManager or GridLayoutManager, you can use
int findFirstVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
For example:
GridLayoutManager layoutManager = ((GridLayoutManager)mRecyclerView.getLayoutManager());
int firstVisiblePosition = layoutManager.findFirstVisibleItemPosition();
For LinearLayoutManager, first/last depends on the adapter ordering. Don't query children from RecyclerView; LayoutManager may prefer to layout more items than visible for caching.
For those who have a logic to be implemented inside the RecyclerView adapter, you can still use the #ernesto approach combined with an on scrollListener to get what you want as the RecyclerView is consulted.
Inside the adapter you will have something like this:
#Override
public void onAttachedToRecyclerView(#NonNull RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
if(manager instanceof LinearLayoutManager && getItemCount() > 0) {
LinearLayoutManager llm = (LinearLayoutManager) manager;
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int visiblePosition = llm.findFirstCompletelyVisibleItemPosition();
if(visiblePosition > -1) {
View v = llm.findViewByPosition(visiblePosition);
//do something
v.setBackgroundColor(Color.parseColor("#777777"));
}
}
});
}
}
Finally, I found a solution to know if the current item is visible, from the onBindViewHolder event in the adapter.
The key is the method isViewPartiallyVisible from LayoutManager.
In your adapter, you can get the LayoutManager from the RecyclerView, which you get as parameter from the onAttachedToRecyclerView event.
You can use recyclerView.getChildAt() to get each visible child, and setting some tag convertview.setTag(index) on these view in adapter code will help you to relate it with adapter data.
Addendum:
The proposed functions findLast...Position() do not work correctly in a scenario with a collapsing toolbar while the toolbar is expanded.
It seems that the recycler view has a fixed height, and while the toolbar is expanded, the recycler is moved down, partially out of the screen. As a consequence the results of the proposed functions are too high. Example: The last visible item is told to be #9, but in fact item #7 is the last one that is on screen.
This behaviour is also the reason why my view often failed to scroll to the correct position, i.e. scrollToPosition() did not work correctly (I finally collapsed the toolbar programmatically).
Every answer above is correct and I would like to add also a snapshot from my working codes.
recycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
// Some code when initially scrollState changes
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// Some code while the list is scrolling
LinearLayoutManager lManager = (LinearLayoutManager) recyclerView.getLayoutManager();
int firstElementPosition = lManager.findFirstVisibleItemPosition();
}
});
Following Linear / Grid LayoutManager methods can be used to check which items are visible.
int findFirstVisibleItemPosition();
int findLastVisibleItemPosition();
int findFirstCompletelyVisibleItemPosition();
int findLastCompletelyVisibleItemPosition();
and if you want to track is item visible on screen for some threshold then you can refer to the following blog.
https://proandroiddev.com/detecting-list-items-perceived-by-user-8f164dfb1d05
For StaggeredGridLayoutManager do this:
RecyclerView rv = findViewById(...);
StaggeredGridLayoutManager lm = new StaggeredGridLayoutManager(...);
rv.setLayoutManager(lm);
And to get visible item views:
int[] viewsIds = lm.findFirstCompletelyVisibleItemPositions(null);
ViewHolder firstViewHolder = rvPlantios.findViewHolderForLayoutPosition(viewsIds[0]);
View itemView = viewHolder.itemView;
Remember to check if it is empty.
You can find the first and last visible children of the recycle view and check if the view you're looking for is in the range:
var visibleChild: View = rv.getChildAt(0)
val firstChild: Int = rv.getChildAdapterPosition(visibleChild)
visibleChild = rv.getChildAt(rv.childCount - 1)
val lastChild: Int = rv.getChildAdapterPosition(visibleChild)
println("first visible child is: $firstChild")
println("last visible child is: $lastChild")
For those who are looking for an answer in Kotlin:
fun getVisibleItem(recyclerView : RecyclerView) {
recyclerView.addOnScrollListener(object: RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if(newState == RecyclerView.SCROLL_STATE_IDLE) {
val index = (recyclerView.layoutManager.findFirstVisibleItemPosition
//use this index for any operation you want to perform on the item visible on screen. eg. log(arrayList[index])
}
}
})
}
You can explore other methods for getting the position as per your use case.
int findFirstCompletelyVisibleItemPosition()
int findLastVisibleItemPosition()
int findLastCompletelyVisibleItemPosition()
if the visible item position is different from the item position toast message will show on the screen.
myRecyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
LinearLayoutManager manager= (LinearLayoutManager) myRecyclerview.getLayoutManager();
assert manager != null;
int visiblePosition = manager.findLastCompletelyVisibleItemPosition();
if(visiblePosition > -1&&a!=visiblePosition) {
Toast.makeText(context,String.valueOf(visiblePosition),Toast.LENGTH_SHORT).show();
//do something
a=visiblePosition;
}
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
//Some code while the list is scrolling
}
});