How can i calculate the height of the first visible item in my recyclerview ?
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
switch (newState) {
case RecyclerView.SCROLL_STATE_IDLE:
Log.d("scroll_stop","The RecyclerView is not scrolling : ");
View firstItemView = mGLM.findViewByPosition(mGLM.findFirstVisibleItemPosition());
View mVizibleView= mPlm.findViewByPosition(mGLM.findFirstVisibleItemPosition());
}
});
But this give me the full height of the view
Taking the Size of any RecyclerView Item is pointless, If you getHeight() or getWidth() of any item it's just gonna give a Null Error and your app is gonna crash.
What you can do, Is to Use your ViewHolder from recyclerView Adapter and First set a Specific Height to any Item you want and Then use that Height somewhere Else.
Look at the Code Below, Maybe helps:
class myViewHolder extends RecyclerView.ViewHolder {
RemaltiveLayout itemLayout;
public myViewHolder(View itemView) {
super(itemView);
itemLayout = (RemaltiveLayout) itemView.findViewById(R.id.myItemLayout);
itemLayout.getLayoutParams().height = res.getDimensionPixelSize(R.dimen.height_value);
}
You should be able to use item at a specific location position as well
This is not gonna work with Width though, cause items are always being stretched to fill columns of layoutManager
Steps to get first item height:
Get the layout manager from the recyclerview reference in onScrolled()
Get the first the visible item position using layoutManager.findFirstVisibleItemPosition()
If fist visible item position is 0 then get the 0th child height layoutManager.getChildAt(0)
Sample code:
RecyclerView.OnScrollListener scrollListener = new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
LinearLayoutManager layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
if (layoutManager != null) {
int child0Height = 0;
int currentFirstVisibleItem = layoutManager.findFirstVisibleItemPosition();
if (currentFirstVisibleItem == 0) {
final View childAt0 = layoutManager.getChildAt(0);
if (childAt0 != null) {
child0Height = childAt0.getHeight();
}
}
}
}
};
Related
I have an imageView and a textView inside a cardView.
The alpha of the cardView is set to .5f.
The cardView is used in a vertical recyclerView.
What I'm trying to do here is as the user scrolls through the reyclerView the alpha of the completely visible cardView should always change to 1f and for the non-completely visible cardViews alpha stays .5f.
There is only one completely visible cardView at a time.
Here is what I tried but it doesn't work.
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int center = recyclerView.getHeight() / 2;
View centerView = recyclerView.findChildViewUnder( recyclerView.getTop(), center);
int centerPos = recyclerView.getChildAdapterPosition(centerView);
if (prevCenterPos != centerPos) {
// dehighlight the previously highlighted view
View prevView =
recyclerView.getLayoutManager().findViewByPosition(prevCenterPos);
if (prevView != null) {
prevView.setAlpha(.5f);
}
// highlight view in the middle
if (centerView != null) {
prevView.setAlpha(1f);
}
prevCenterPos = centerPos;
}
}
As you are finding center point with this
int center = recyclerView.getHeight() / 2;
which is not proper way you should use:
mLayoutManager.findFirstCompletelyVisibleItemPosition()
try this:
val firstCompelteVisible = mLayoutManager.findFirstCompletelyVisibleItemPosition()
val centerView =
recyclerView.layoutManager!!.findViewByPosition(firstCompelteVisible)
if (prevCenterPos != centerPos) {
// dehighlight the previously highlighted view
val prevView =
recyclerView.layoutManager!!.findViewByPosition(prevCenterPos)
if (prevView != null) {
prevView.alpha = .5f
}
// highlight view in the middle
if (centerView != null) {
prevView!!.alpha = 1f
}
prevCenterPos = centerPos
}
I hope this will work.
I have a RecyclerView (say, rootRecyclerView) that can have different kinds of rows depending on some API response. I implemented one of them is a horizontal ViewPager2 and another one is implemented with horizontal RecyclerView (say, childRecyclerView).
The rootRecyclerView swipes vertically whereas the viewPager2 and childRecyclerView swipes horizontally.
The Problem:
When I swipe on the screen, if the swipe is on the the viewPager2 or childRecyclerView, the swipe MUST go perfectly straight horizontally. Otherwise, they won't scroll horizontally; the swipe is taken by the rootRecyclerView and so the you would see vertical movement.
So, this happens because your thumb would move in a curved/circular direction creating movement in both the X axis and Y axis, and the so the rootRecyclerView intercepts the swipe creating this unpleasant user experience.
I did try to solve the issue, such as adding an OnItemTouchListener to the childRecyclerView like this:
private float Y_BUFFER = ViewConfiguration.get(getContext())
.getScaledPagingTouchSlop(); // 10;
private float preX = 0f;
private float preY = 0f;
childRecyclerView.addOnItemTouchListener(new RecyclerView.OnItemTouchListener() {
#Override
public boolean onInterceptTouchEvent(#NonNull RecyclerView rv, #NonNull MotionEvent e) {
if(e.getAction()==MotionEvent.ACTION_DOWN){
childRecyclerView.getParent().requestDisallowInterceptTouchEvent(true);
}
if(e.getAction() == MotionEvent.ACTION_MOVE){
if (Math.abs(e.getX() - preX) > Math.abs(e.getY() - preY)) {
childRecyclerView.getParent().requestDisallowInterceptTouchEvent(true);
} else if (Math.abs(e.getY() - preY) > Y_BUFFER) {
childRecyclerView.getParent().requestDisallowInterceptTouchEvent(false);
}
}
preX = e.getX();
preY = e.getY();
return false;
}
// ... rest of the code
It solves the problem only for the childRecyclerView, but I could not solve it for the ViewPager2.
I have also tried to use GestureDetector as described in this answer link, and some other combinations of code, but I could not make it work.
Could anyone help me?
Okay, so after some research, I came to the conclusion of substituting my ViewPager2 with a recyclerView that will 'behave like' a viewPager :/ .
First I replaced my viewPager2 with a horizontal recyclerView. To make it behave like a viewpager, use SnapHelper.
RecyclerView childRecyclerView2 = findViewById(R.id.previously_viewPager);
// other init like setup layout manager, adapter etc
SnapHelper snapHelper = new PagerSnapHelper();
snapHelper.attachToRecyclerView(replacedRecyclerView); // <-- this makes out rv behave like a viewPager
After that, you have to add an OnItemTouchListener and override onInterceptTouchEvent just like the code segment in my question:
childRecyclerView2.addOnItemTouchListener(new RecyclerView.OnItemTouchListener() {
#Override
public boolean onInterceptTouchEvent(#NonNull RecyclerView rv, #NonNull MotionEvent e) {
// same as the code segment in the question,
//so skipping this part.
//just copy it from my question
}
// ...
}
Optional:
In viewPager2, you can get the current focus with getCurrentItem(), but since we have replaced out viewpager2 with recyclerview, we don't have that method. So, we need to implement our own equivalent version. If you are a Kotlin guy, you can directly jump to the reference 2 and skip this part. Here is the java version if you need, I'll skip the explanation though.
Create SnapHelperExt.java
public class SnapHelperExt {
public SnapHelperExt(){}
public int getSnapPosition(RecyclerView recyclerView, SnapHelper snapHelper){
RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
View snapView = snapHelper.findSnapView(layoutManager);
if (snapView != null) {
return layoutManager.getPosition(snapView);
}else{
return -1;
}
}
}
Next create an interface OnSnapPositionChangeListener as our listener :
public interface OnSnapPositionChangeListener {
void onSnapPositionChange(int position);
}
After that, create SnapOnScrollListener.java:
public class SnapOnScrollListener extends RecyclerView.OnScrollListener {
public enum Behavior {
NOTIFY_ON_SCROLL,
NOTIFY_ON_SCROLL_STATE_IDLE
}
private SnapHelperExt snapHelperExt;
private SnapHelper snapHelper;
private Behavior behavior;
private OnSnapPositionChangeListener onSnapPositionChangeListener;
private int snapPosition = RecyclerView.NO_POSITION;
public SnapOnScrollListener(SnapHelper snapHelper, Behavior behavior, OnSnapPositionChangeListener onSnapPositionChangeListener){
this.snapHelper = snapHelper;
this.behavior = behavior;
this.onSnapPositionChangeListener = onSnapPositionChangeListener;
this.snapHelperExt = new SnapHelperExt();
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (behavior == Behavior.NOTIFY_ON_SCROLL) {
maybeNotifySnapPositionChange(recyclerView);
}
}
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (behavior == Behavior.NOTIFY_ON_SCROLL_STATE_IDLE
&& newState == RecyclerView.SCROLL_STATE_IDLE) {
maybeNotifySnapPositionChange(recyclerView);
}
}
private void maybeNotifySnapPositionChange(RecyclerView recyclerView){
int prevPosition = this.snapHelperExt.getSnapPosition(recyclerView, snapHelper);
boolean snapPositionIsChanged = (this.snapPosition!=prevPosition);
if(snapPositionIsChanged){
onSnapPositionChangeListener.onSnapPositionChange(prevPosition);
this.snapPosition = prevPosition;
}
}
}
Finally, use it in this way:
SnapOnScrollListener snapOnScrollListener = new SnapOnScrollListener(
snapHelper,
SnapOnScrollListener.Behavior.NOTIFY_ON_SCROLL,
position -> {
Log.e(TAG, "currently focused page no = "+position);
// your code here, do whatever you want
}
);
childRecyclerView2.addOnScrollListener(snapOnScrollListener);
References:
create-viewpager-using-recyclerview
detecting-snap-changes-with-androids-recyclerview
I haven't been able to find any post about it...
We have the good old RecyclerView.ItemDecoration code (taken from Suleiman's Mansonry Github project):
public class SpacesItemDecoration extends RecyclerView.ItemDecoration {
private final int mSpace;
public SpacesItemDecoration(int space) {
this.mSpace = space;
}
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
outRect.left = mSpace;
outRect.right = mSpace;
outRect.bottom = mSpace;
// Add top margin only for the first item to avoid double space between items
if (parent.getChildAdapterPosition(view) == 0)
outRect.top = mSpace;
}
}
I want to have a condition that sets mSpace (offset/margin) depending on the current LayoutManager in the RecyclerView.
For example:
if(/* LayoutManager is LinearLayoutManager*/){
//Set larger margin
}else{
//Set lower margin
}
So... as I was re-reading the question to check if anything was missing, and I realized that you actually get a RecyclerView reference (parent) as an argument of getItemOffsets().
So you can just call parent.getLayoutManager() from inside the function.
Example:
#Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (parent.getLayoutManager() instanceof LinearLayoutManager){
margin = 2;
}else if (parent.getLayoutManager() instanceof StaggeredGridLayoutManager){
margin = 1;
}else{
margin = 0;
}
//Do magic
}
How to get the scrollposition in Recyclerview or the Layoutmanager?
I can measure the scrollposition by adding an OnScrollListener, but when the Orientation changes scrollDy is 0.
mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
int scrollDy = 0;
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
scrollDy += dy;
}
});
For future use, If you are switching between Fragments within the same activity and all you want to do is save scroll-position for recyclerview and then restore recyclerview to the same scroll-position, you can do as follows:
In your onStop()/onDestroyView()/onPause() whatever callback is more appropriate, do this:
Parcelable recylerViewState = recyclerView.getLayoutManager().onSaveInstanceState();
And In your onStart()/onCreateView()/onResume() whatever callback is more appropriate, do this:
recyclerView.getLayoutManager().onRestoreInstanceState(recylerViewState);
This way you can successfully keep your recyclerView's state in a parcelable and restore it whenever you want.
You cannot get it because it does not really exist. LayoutManager only knows about the views on screen, it does not know the views before, what their size is etc.
The number you can count using the scroll listener is not reliable because if data changes, RecyclerView will do a fresh layout calculation and will not try to re-calculate a real offset (you'll receive an onScroll(0, 0) if views moved).
RecyclerView estimates this value for scrollbars, you can use the same methods from View class.
computeHorizontalScrollExtent
computeHorizontalScrollRange
computeHorizontalScrollOffset
These methods have their vertical counterparts as well.
I came to the question just wanting to get the item position index that is currently scrolled to. For others who want to do the same, you can use the following:
LinearLayoutManager myLayoutManager = myRecyclerView.getLayoutManager();
int scrollPosition = myLayoutManager.findFirstVisibleItemPosition();
You can also get these other positions:
findLastVisibleItemPosition()
findFirstCompletelyVisibleItemPosition()
findLastCompletelyVisibleItemPosition()
Thanks to this answer for help with this. It also shows how to save and restore the scroll position.
recyclerView.computeVerticalScrollOffset() does the trick.
Found a work around to getting last scrolled position within the RecyclerView with credits to Suragch solution...
Declare a globally accessible LinearLayoutManager so a to be able to access it within inner methods...
When ever the populateChatAdapter method is called, if its the first call the scroll to position will be the last sent message and if the user had scrolled to view previous messages and method is called again to update new messages then they will retain their last scrolled to position...
LinearLayoutManager linearLayoutManager;
int lastScrollPosition = 0;
RecyclerView messages_recycler;
Initiate them...
messages_recycler = findViewById(R.id.messages_recycler);
linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setStackFromEnd(true);
messages_recycler.setLayoutManager(linearLayoutManager);
On your populate adapter method
private void populateChatAdapter(ObservableList<ChatMessages> msgs) {
if (lastScrollPosition==0) lastScrollPosition = msgs.size()-1;
ChatMessagesRecycler adapter = new ChatMessagesRecycler(msgs);
messages_recycler.setAdapter(adapter);
messages_recycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
lastScrollPosition = linearLayoutManager.findLastCompletelyVisibleItemPosition();
}
});
messages_recycler.scrollToPosition(lastScrollPosition);
}
You have to read scrollDy in
public void onScrollStateChanged(RecyclerView recyclerView, int newState)
then you can get recyclerView's scroll position
To get ScroolPosition try this:
You will need this:
mLayoutManager = new LinearLayoutManager(getApplicationContext(), LinearLayoutManager.HORIZONTAL, false);
And then get the position of the mLayoutManager (like this):
recyclerView
.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
int pos = mLayoutManager.getPosition(v);
RecyclerView.ViewHolder viewHolder = recyclerView.findViewHolderForAdapterPosition(pos);
}
});
With this "pos" you get the position, startin with the 0.
int pos = mLayoutManager.getPosition(v);
I have a RecyclerView with Expandable Child Views, when the child ViewGroup is clicked it inflates an amount of views animating the ViewGroup height from 0 to the measured viewgroup height, like the following gif:
The problem is: I'm calling smoothScrollToPosition on recyclerView, it smooth scroll to the view position, but it considers the current view height, which is still not expanded, in the above gif i'm touching on the under view of the recyclerview, which dont scroll to position because the view is already visible, but when i touch again (calling the smoothscrolltoposition again) it scroll the view to the correct position, because the view is already expanded.
Is there any approach to scroll the view to the top of screen or just scroll to make content visible?
For references:
This is the method called to inflate the views:
collapsible_content.removeAllViews();
for(int i = 0; i < 5; i++) {
View link_view = getLayoutInflater().inflate(R.layout.list_item_timeline_step_link, collapsible_content, false);
TextView text = (TextView) link_view.findViewById(R.id.step_link_text);
text.setText("Test");
collapsible_content.addView(link_view);
}
And this is my method to expand:
public void toggle() {
collapsible_content.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
Animation a;
if (mExpanded) {
a = new ExpandAnimation(collapsible_content.getLayoutParams().height, 0);
} else {
a = new ExpandAnimation(collapsible_content.getLayoutParams().height, getMeasuredHeight());
}
a.setDuration(mAnimationDuration);
collapsible_content.startAnimation(a);
mExpanded = !mExpanded;
}
And the animation:
private class ExpandAnimation extends Animation {
private final int mStartHeight;
private final int mDeltaHeight;
public ExpandAnimation(int startHeight, int endHeight) {
mStartHeight = startHeight;
mDeltaHeight = endHeight - startHeight;
}
#Override
protected void applyTransformation(float interpolatedTime,
Transformation t) {
final int newHeight = (int) (mStartHeight + mDeltaHeight *
interpolatedTime);
collapsible_content getLayoutParams().height = newHeight;
if (newHeight <= 0) {
collapsible_content setVisibility(View.GONE);
} else {
collapsible_content setVisibility(View.VISIBLE);
}
collapsible_content requestLayout();
}
#Override
public boolean willChangeBounds() {
return true;
}
}
My solution was to constant check for view bottom within applyTransformation method, and compare it with RecyclerView height, if the bottom get higher than the RV height, i scroll by the diff values:
final int bottom = collapsible_content.getBottom();
final int listViewHeight = mRecyclerView.getHeight();
if (bottom > listViewHeight) {
final int top = collapsible_content.getTop();
if (top > 0) {
mRecyclerView.smoothScrollBy(0, Math.min(bottom - listViewHeight + mRecyclerView.getPaddingBottom(), top));
}
}
The trick was to use Math.min to get the view top, so it don't scroll up making the top not visible.
Solution based on ListViewAnimations
Add an animationlistener and start the scrolling of the recyclerview after the expanding animation is finished.