ChannelsPosterPrefetcher.java revision 0cc0713c1bf8027642987b750b80217569d2932a 
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
17package com.android.tv.menu;
18
19import android.content.Context;
20import android.os.Handler;
21import android.os.Looper;
22import android.os.Message;
23import android.support.annotation.MainThread;
24import android.support.annotation.NonNull;
25import android.util.Log;
26import com.android.tv.R;
27import com.android.tv.common.SoftPreconditions;
28import com.android.tv.common.WeakHandler;
29import com.android.tv.data.ChannelImpl;
30import com.android.tv.data.Program;
31import com.android.tv.data.ProgramDataManager;
32import com.android.tv.data.api.Channel;
33import java.util.List;
34
35/** A poster image prefetcher to show the program poster art in the Channels row faster. */
36public class ChannelsPosterPrefetcher {
37    private static final String TAG = "PosterPrefetcher";
38    private static final boolean DEBUG = false;
39    private static final int MSG_PREFETCH_IMAGE = 1000;
40    private static final int ONDEMAND_POSTER_PREFETCH_DELAY_MILLIS = 500; // 500 milliseconds
41
42    private final ProgramDataManager mProgramDataManager;
43    private final ChannelsRowAdapter mChannelsAdapter;
44    private final int mPosterArtWidth;
45    private final int mPosterArtHeight;
46    private final Context mContext;
47    private final Handler mHandler = new PrefetchHandler(this);
48
49    private boolean isCanceled;
50
51    /** Create {@link ChannelsPosterPrefetcher} object with given parameters. */
52    public ChannelsPosterPrefetcher(
53            Context context, ProgramDataManager programDataManager, ChannelsRowAdapter adapter) {
54        mProgramDataManager = programDataManager;
55        mChannelsAdapter = adapter;
56        mPosterArtWidth =
57                context.getResources().getDimensionPixelSize(R.dimen.card_image_layout_width);
58        mPosterArtHeight =
59                context.getResources().getDimensionPixelSize(R.dimen.card_image_layout_height);
60        mContext = context.getApplicationContext();
61    }
62
63    /** Start prefetching of program poster art of recommendation. */
64    public void prefetch() {
65        SoftPreconditions.checkState(!isCanceled, TAG, "Prefetch called after cancel was called.");
66        if (isCanceled) {
67            return;
68        }
69        if (DEBUG) Log.d(TAG, "startPrefetching()");
70        /*
71         * When a user browse channels, this method could be called many times. We don't need to
72         * prefetch the intermediate channels. So ignore previous schedule.
73         */
74        mHandler.removeMessages(MSG_PREFETCH_IMAGE);
75        mHandler.sendMessageDelayed(
76                mHandler.obtainMessage(MSG_PREFETCH_IMAGE), ONDEMAND_POSTER_PREFETCH_DELAY_MILLIS);
77    }
78
79    /** Cancels pending and current prefetch requests. */
80    public void cancel() {
81        isCanceled = true;
82        mHandler.removeCallbacksAndMessages(null);
83    }
84
85    @MainThread // ProgramDataManager.getCurrentProgram must be called from the main thread
86    private void doPrefetchImages() {
87        if (DEBUG) Log.d(TAG, "doPrefetchImages() started");
88
89        // This executes on the main thread, but since the item list is expected to be about 5 items
90        // and ImageLoader spawns an async task so this is fast enough. 1 ms in local testing.
91        List<ChannelsRowItem> items = mChannelsAdapter.getItemList();
92        if (items != null) {
93            for (ChannelsRowItem item : items) {
94                if (isCanceled) {
95                    return;
96                }
97                Channel channel = item.getChannel();
98                if (!ChannelImpl.isValid(channel)) {
99                    continue;
100                }
101                channel.prefetchImage(
102                        mContext,
103                        Channel.LOAD_IMAGE_TYPE_CHANNEL_LOGO,
104                        mPosterArtWidth,
105                        mPosterArtHeight);
106                Program program = mProgramDataManager.getCurrentProgram(channel.getId());
107                if (program != null) {
108                    program.prefetchPosterArt(mContext, mPosterArtWidth, mPosterArtHeight);
109                }
110            }
111        }
112        if (DEBUG) {
113            Log.d(
114                    TAG,
115                    "doPrefetchImages() finished. ImageLoader may still have async tasks for "
116                            + "channels "
117                            + items);
118        }
119    }
120
121    private static class PrefetchHandler extends WeakHandler<ChannelsPosterPrefetcher> {
122        public PrefetchHandler(ChannelsPosterPrefetcher ref) {
123            // doPrefetchImages must be called from the main thread.
124            super(Looper.getMainLooper(), ref);
125        }
126
127        @Override
128        @MainThread
129        public void handleMessage(Message msg, @NonNull ChannelsPosterPrefetcher prefetcher) {
130            switch (msg.what) {
131                case MSG_PREFETCH_IMAGE:
132                    prefetcher.doPrefetchImages();
133                    break;
134            }
135        }
136    }
137}
138