1 /* 2 * Copyright (C) 2015 The Android Open Source Project 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.android.tv.menu; 18 19 import android.content.Context; 20 import android.os.Handler; 21 import android.os.Looper; 22 import android.os.Message; 23 import android.support.annotation.MainThread; 24 import android.support.annotation.NonNull; 25 import android.util.Log; 26 27 import com.android.tv.R; 28 import com.android.tv.common.SoftPreconditions; 29 import com.android.tv.common.WeakHandler; 30 import com.android.tv.data.Channel; 31 import com.android.tv.data.Program; 32 import com.android.tv.data.ProgramDataManager; 33 34 import java.util.List; 35 36 /** 37 * A poster image prefetcher to show the program poster art in the Channels row faster. 38 */ 39 public class ChannelsPosterPrefetcher { 40 private static final String TAG = "PosterPrefetcher"; 41 private static final boolean DEBUG = false; 42 private static final int MSG_PREFETCH_IMAGE = 1000; 43 private static final int ONDEMAND_POSTER_PREFETCH_DELAY_MILLIS = 500; // 500 milliseconds 44 45 private final ProgramDataManager mProgramDataManager; 46 private final ChannelsRowAdapter mChannelsAdapter; 47 private final int mPosterArtWidth; 48 private final int mPosterArtHeight; 49 private final Context mContext; 50 private final Handler mHandler = new PrefetchHandler(this); 51 52 private boolean isCanceled; 53 54 /** 55 * Create {@link ChannelsPosterPrefetcher} object with given parameters. 56 */ 57 public ChannelsPosterPrefetcher(Context context, ProgramDataManager programDataManager, 58 ChannelsRowAdapter adapter) { 59 mProgramDataManager = programDataManager; 60 mChannelsAdapter = adapter; 61 mPosterArtWidth = context.getResources().getDimensionPixelSize( 62 R.dimen.card_image_layout_width); 63 mPosterArtHeight = context.getResources().getDimensionPixelSize( 64 R.dimen.card_image_layout_height); 65 mContext = context.getApplicationContext(); 66 } 67 68 /** 69 * Start prefetching of program poster art of recommendation. 70 */ 71 public void prefetch() { 72 SoftPreconditions.checkState(!isCanceled, TAG, "Prefetch called after cancel was called."); 73 if (isCanceled) { 74 return; 75 } 76 if (DEBUG) Log.d(TAG, "startPrefetching()"); 77 /* 78 * When a user browse channels, this method could be called many times. We don't need to 79 * prefetch the intermediate channels. So ignore previous schedule. 80 */ 81 mHandler.removeMessages(MSG_PREFETCH_IMAGE); 82 mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_PREFETCH_IMAGE), 83 ONDEMAND_POSTER_PREFETCH_DELAY_MILLIS); 84 } 85 86 /** 87 * Cancels pending and current prefetch requests. 88 */ 89 public void cancel() { 90 isCanceled = true; 91 mHandler.removeCallbacksAndMessages(null); 92 } 93 94 @MainThread // ProgramDataManager.getCurrentProgram must be called from the main thread 95 private void doPrefetchImages() { 96 if (DEBUG) Log.d(TAG, "doPrefetchImages() started"); 97 98 // This executes on the main thread, but since the item list is expected to be about 5 items 99 // and ImageLoader spawns an async task so this is fast enough. 1 ms in local testing. 100 List<ChannelsRowItem> items = mChannelsAdapter.getItemList(); 101 if (items != null) { 102 for (ChannelsRowItem item : items) { 103 if (isCanceled) { 104 return; 105 } 106 Channel channel = item.getChannel(); 107 if (!Channel.isValid(channel)) { 108 continue; 109 } 110 channel.prefetchImage(mContext, Channel.LOAD_IMAGE_TYPE_CHANNEL_LOGO, 111 mPosterArtWidth, mPosterArtHeight); 112 Program program = mProgramDataManager.getCurrentProgram(channel.getId()); 113 if (program != null) { 114 program.prefetchPosterArt(mContext, mPosterArtWidth, mPosterArtHeight); 115 } 116 } 117 } 118 if (DEBUG) { 119 Log.d(TAG, "doPrefetchImages() finished. ImageLoader may still have async tasks for " 120 + "channels " + items); 121 } 122 } 123 124 private static class PrefetchHandler extends WeakHandler<ChannelsPosterPrefetcher> { 125 public PrefetchHandler(ChannelsPosterPrefetcher ref) { 126 // doPrefetchImages must be called from the main thread. 127 super(Looper.getMainLooper(), ref); 128 } 129 130 @Override 131 @MainThread 132 public void handleMessage(Message msg, @NonNull ChannelsPosterPrefetcher prefetcher) { 133 switch (msg.what) { 134 case MSG_PREFETCH_IMAGE: 135 prefetcher.doPrefetchImages(); 136 break; 137 } 138 } 139 } 140 } 141