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