A wrapped {@link android.support.v7.widget.RecyclerView} view with an empty view functionality like {@link android.widget.ListView}

EmptyRecyclerView.java

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 longkai
 *
 * The software shall be used for good, not evil.
 */

package com.example.widget;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.View;

/**
 * A wrapped {@link android.support.v7.widget.RecyclerView} view with an empty view functionality like {@link android.widget.ListView} 
 * 
 * use this view you must provide an empty view whose view hierarchy is the same as this view and its initial visibility is GONE
 * 
 * @author longkai
 */
public class EmptyRecyclerView extends RecyclerView {
  private View mEmptyView;
  
  /** If lazy, it means the first time the adapter attached with zero items, the empty view(if exist) won' t show */
  private boolean mLazy = true;

  private boolean mObserverAttached = false;

  public EmptyRecyclerView(Context context) {
    this(context, null);
  }

  public EmptyRecyclerView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

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

  public void setEmptyView(View emptyView) {
    mEmptyView = emptyView;
  }

  public void setLazy(boolean lazy) {
    mLazy = lazy;
  }

  public void setEager(boolean eager) {
    mLazy = !eager;
  }

  public boolean isLazy() {
    return mLazy;
  }

  public boolean isEager() {
    return !mLazy;
  }

  private void updateEmptyStatus(boolean empty) {
    if (empty) {
      setVisibility(GONE);
      if (mEmptyView != null) {
        mEmptyView.setVisibility(VISIBLE);
      }
    } else {
      setVisibility(VISIBLE);
      if (mEmptyView != null) {
        mEmptyView.setVisibility(GONE);
      }
    }
  }

  public boolean isEmpty() {
    Adapter adapter = getAdapter();
    return adapter == null ? true : adapter.getItemCount() == 0;
  }

  @Override protected void onDetachedFromWindow() {
    super.onDetachedFromWindow();
    Adapter adapter = getAdapter();
    if (adapter != null && mObserverAttached) {
      adapter.unregisterAdapterDataObserver(mObserver);
      mObserverAttached = false;
    }
  }

  @Override public void setAdapter(Adapter adapter) {
    super.setAdapter(adapter);

    adapter.registerAdapterDataObserver(mObserver);
    mObserverAttached = true;

    if (isEager()) {
      updateEmptyStatus(isEmpty());
    }
  }

  private AdapterDataObserver mObserver = new AdapterDataObserver() {
    @Override public void onChanged() {
      super.onChanged();
      updateEmptyStatus(isEmpty());
    }

    @Override public void onItemRangeChanged(int positionStart, int itemCount) {
      super.onItemRangeChanged(positionStart, itemCount);
      updateEmptyStatus(isEmpty());
    }

    @Override public void onItemRangeInserted(int positionStart, int itemCount) {
      super.onItemRangeInserted(positionStart, itemCount);
      updateEmptyStatus(isEmpty());
    }

    @Override public void onItemRangeRemoved(int positionStart, int itemCount) {
      super.onItemRangeRemoved(positionStart, itemCount);
      updateEmptyStatus(isEmpty());
    }
  };
}