RecyclerView doesn't have an emptyView support, we gotta fix that

EmptyRecyclerView.java

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.View;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

public class EmptyRecyclerView extends RecyclerView {
  @Nullable View emptyView;

  public EmptyRecyclerView(Context context) { super(context); }

  public EmptyRecyclerView(Context context, AttributeSet attrs) { super(context, attrs); }

  public EmptyRecyclerView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  void checkIfEmpty() {
    if (emptyView != null) {
      emptyView.setVisibility(getAdapter().getItemCount() > 0 ? GONE : VISIBLE);
    }
  }

  final @NotNull AdapterDataObserver observer = new AdapterDataObserver() {
    @Override public void onChanged() {
      super.onChanged();
      checkIfEmpty();
    }
  };

  @Override public void setAdapter(@Nullable Adapter adapter) {
    final Adapter oldAdapter = getAdapter();
    if (oldAdapter != null) {
      oldAdapter.unregisterAdapterDataObserver(observer);
    }
    super.setAdapter(adapter);
    if (adapter != null) {
      adapter.registerAdapterDataObserver(observer);
    }
  }

  public void setEmptyView(@Nullable View emptyView) {
    this.emptyView = emptyView;
    checkIfEmpty();
  }
}

@adelnizamutdinov
Hi, I think there's a small typo on line 25. Shouldn't it be @NonNull instead of @NotNull?

It is also not working without implementing onItemRangeInserted in the observer. I'm using FirebaseUI.

I have the same question, where is the emptyView attached?

Its good but what happened if we had to add one more observer to for lazy loading/paging?