RecyclerView LayoutManager findViewByPosition returns null

Question

I'm interested in what is the right and first possible moment to get size of first item of RecyclerView?

I've tried to use:

recyclerView.setLayoutManager(new GridLayoutManager(context, 2));
recyclerView.setAdapter(new MyDymmyGridRecyclerAdapter(context));
recyclerView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
     @Override
     public void onGlobalLayout() {
         recyclerView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
         View firstRecyclerViewItem = recyclerView.getLayoutManager().findViewByPosition(0);
         // firstRecyclerViewItem is null here
     }
});

but it returns null at this moment.

Answer 1

If you're using OnGlobalLayoutListener you should remember onGlobalLayout can be called multiple times. Some of those calls can happen even before Layout is ready (and by ready I mean the moment when you can get dimensions of a View by calling view.getHeight() or view.getWidth()). So the proper way of implementing your approach would be:

recyclerView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
     @Override
     public void onGlobalLayout() {
         int width = recyclerView.getWidth();
         int height = recyclerView.getHeight();
         if (width > 0 && height > 0) {
             if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN) {
                 recyclerView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
             } else {
                 recyclerView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
             }
         }

         View firstRecyclerViewItem = recyclerView.getLayoutManager().findViewByPosition(0);
     }
});

Apart from that you still need to be sure that at the time of findViewByPosition(0) call:

1. Your RecyclerView's Adapter has at least one data element.
2. View at position 0 is currently visible in RecyclerView

Tell me if that fixes your issue, if not there is still another way of doing what you need.