1 /* 2 * Copyright 2015 Google Inc. All rights reserved. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.example.android.xyztouristattractions.ui; 18 19 import android.content.Context; 20 import android.support.v7.widget.RecyclerView; 21 import android.util.AttributeSet; 22 import android.view.View; 23 24 /** 25 * Simple RecyclerView subclass that supports providing an empty view (which 26 * is displayed when the adapter has no data and hidden otherwise). 27 */ 28 public class AttractionsRecyclerView extends RecyclerView { 29 private View mEmptyView; 30 31 private AdapterDataObserver mDataObserver = new AdapterDataObserver() { 32 @Override 33 public void onChanged() { 34 super.onChanged(); 35 updateEmptyView(); 36 } 37 }; 38 39 public AttractionsRecyclerView(Context context) { 40 super(context); 41 } 42 43 public AttractionsRecyclerView(Context context, AttributeSet attrs) { 44 super(context, attrs); 45 } 46 47 public AttractionsRecyclerView(Context context, AttributeSet attrs, int defStyle) { 48 super(context, attrs, defStyle); 49 } 50 51 /** 52 * Designate a view as the empty view. When the backing adapter has no 53 * data this view will be made visible and the recycler view hidden. 54 * 55 */ 56 public void setEmptyView(View emptyView) { 57 mEmptyView = emptyView; 58 } 59 60 @Override 61 public void setAdapter(RecyclerView.Adapter adapter) { 62 if (getAdapter() != null) { 63 getAdapter().unregisterAdapterDataObserver(mDataObserver); 64 } 65 if (adapter != null) { 66 adapter.registerAdapterDataObserver(mDataObserver); 67 } 68 super.setAdapter(adapter); 69 updateEmptyView(); 70 } 71 72 private void updateEmptyView() { 73 if (mEmptyView != null && getAdapter() != null) { 74 boolean showEmptyView = getAdapter().getItemCount() == 0; 75 mEmptyView.setVisibility(showEmptyView ? VISIBLE : GONE); 76 setVisibility(showEmptyView ? GONE : VISIBLE); 77 } 78 } 79 } 80
