Develop Reference

Deny scroll to first position in recyclerview

I have recycler view with adapter. Need deny user to scroll to item with 0 index, when it was scrolled. F.e user scrolls to 5 item and when scrolls back first visible will be item with index 1.
Will be glad any ideas how to implement this feature.

Use smoothScrollToIndex(1) inside addOnScrollListener of the recycler view.
Keep a if check with !recyclerView.canScrollVertically(-1) there if it succeeded then use like :
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(!recyclerView.canScrollVertically(-1))
{
mRecyclerView.smoothScrollToIndex(1);
}
}});

RecyclerView ScrollY always 0

I have a RecyclerView inside a fragment. I need to be notified of scroll changes, so I added a callback to the ScrollChange event (which corresponds to the SetOnScrollChangeListener in classical Android API):
private void RecyclerViewScrollChange(object sender, View.ScrollChangeEventArgs e)
{
int deltaY = e.ScrollY - e.OldScrollY;
}
The problem is that deltaY is always zero, because both ScrollY and OldScrollY are always zero. I am using vertical linear layout in the recycler view's layout manager, so the vertical dimension ought to be updated. What can cause this problem?

View.SetOnScrollChangeListener() was added in API level 23 which you can see here in the docs: View.SetOnScrollChangeListener()
If your app should support versions before API level 23, a workaround is by adding a ScrollChangeListener to the RecyclerView's `ViewTreeObserver' using AddOnScrollChangedListener() as followed:
_recyclerView.ViewTreeObserver.AddOnScrollChangedListener(param);
Or adding a callback to the ViewTreeObserver's ScrollChanged event

scrolling to Y position is getting using
recyclerView.addOnScrollListener(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);
Log.v("onScrolled", "dx:" + dx + " dy:" + dy);
}
});

Swipe Back Activity Android

I am using swipe back activity in one of my project activity.
Demo Project Which I have implemented
My activity layout contains recyclerview and other components as well. So the problem is when I scroll up my recyclerview items then activity get finished.
However it is working perfectly in Listview.
So is there any way to prevent activity to finish while recyclerview is scrolling ?

I solved by adding a scroll listener.
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int firstVisibleItem = layoutManager.findFirstCompletelyVisibleItemPosition();
if (firstVisibleItem == 0) {
setEnableSwipe(true);
} else {
setEnableSwipe(false);
}
}
});
I don't know if this is the best solution. But it works :)

Hiding FloatingAction items when you scroll to the bottom of a list?

So if you have a RecyclerView that extends to the end of the screen and use a FloatingActionButton or the third-party FloatingActionMenu, then there is a slight problem with cover-up: If you scroll to the end of the list, the floating button covers up part of the row and there is no way to see or get to what's underneath it.
Is there a way Android allows you to:
Detect if your list has a sufficient number of items in it, i.e. if there is a row at the bottom of the screen visible.
and
Slide the buttons out of the way if you scroll down to the very end, and then slide them back in if you start scrolling back up?
Edit: Or, alternatively, add dynamic padding to the end of the RecyclerView that only shows up if you've scrolled all the way down?

The common pattern to solve the problem of covering up parts of UI is to hide FAB as soon as the user starts scrolling down ... You can achieve this by this code fragment (used with RecyclerView):
fDemandsRv.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(dy > 0 ){
if(fFab.isShown()) fFab.hide();
} else {
if(!fFab.isShown()) fFab.show();
}
}
});
If you insist on hiding it on the very end and you are using RecyclerView with LinearLayoutManager, you can check method findLastCompletelyVisibleItemPosition() on the LayoutManager object during the OnScrollListener callback ...

Of course it is possible. The solution was posted here.
The main idea behind it is that FloatingActionButton.Behavior is overriden and changed, so that it reacts to RecyclerView and CoordinatorLayout scrolling.
However, in your case RecyclerViewScrollListener must be different. Here is the implementation:
private class RecyclerViewScrollListener extends RecyclerView.OnScrollListener {
FloatingActionButton mChild;
public RecyclerViewScrollListener(FloatingActionButton child) {
this.mChild = child;
}
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE && recyclerView.canScrollVertically(Integer.MAX_VALUE)) {
mChild.show();
} else {
mChild.hide();
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (!recyclerView.canScrollVertically(Integer.MAX_VALUE)) {
mChild.hide();
}
}
}
Edit:
When filling RecyclerView with data, invoke such function on it in order to disable or enable scrolling:
private void changeCoordinatorLayoutScrollPossibility(final RecyclerView recyclerView) {
new Handler().post(new Runnable() {
#Override
public void run() {
if (recyclerView.getMeasuredHeight() < alertsRecyclerView.computeVerticalScrollRange()) {
recyclerView.setNestedScrollingEnabled(true);
} else {
recyclerView.setNestedScrollingEnabled(false);
}
}
});
}

RecyclerView scroll to top button

I want to add back to top button in my app. I use recyclerview for displaying items. I added button and when I click on it, view is going to top, but my goal is to show this button only if application is scrolled down or up, and my first item is not visible (I hope thats clear explanation). I tried with
LayoutManager.findFirstCompletelyVisibleItemPosition();
and other methods for LayoutManager but without acceptable effects.

My solution is showed below. I add OnScrollListener on my RecyclerView, and when view is scrolled I check if the first item is visible and I set visibility of my button.
MyRecyclerView.addOnScrollListener(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) {
int visibility = (MyLayoutManager.findFirstCompletelyVisibleItemPosition() != 0) ? View.VISIBLE : View.GONE;
btn.setVisibility(visibility);
}
});