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      1 /*
      2  * Copyright (C) 2007 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.camera;
     18 
     19 import com.android.camera.gallery.IImage;
     20 
     21 import android.content.ContentResolver;
     22 import android.graphics.Bitmap;
     23 import android.os.Handler;
     24 import android.provider.MediaStore;
     25 import android.util.Log;
     26 
     27 import java.util.ArrayList;
     28 
     29 /**
     30  * A dedicated decoding thread used by ImageGallery.
     31  */
     32 public class ImageLoader {
     33     @SuppressWarnings("unused")
     34     private static final String TAG = "ImageLoader";
     35 
     36     // Queue of work to do in the worker thread. The work is done in order.
     37     private final ArrayList<WorkItem> mQueue = new ArrayList<WorkItem>();
     38 
     39     // the worker thread and a done flag so we know when to exit
     40     private boolean mDone;
     41     private Thread mDecodeThread;
     42     private ContentResolver mCr;
     43 
     44     public interface LoadedCallback {
     45         public void run(Bitmap result);
     46     }
     47 
     48     public void getBitmap(IImage image,
     49                           LoadedCallback imageLoadedRunnable,
     50                           int tag) {
     51         if (mDecodeThread == null) {
     52             start();
     53         }
     54         synchronized (mQueue) {
     55             WorkItem w = new WorkItem(image, imageLoadedRunnable, tag);
     56             mQueue.add(w);
     57             mQueue.notifyAll();
     58         }
     59     }
     60 
     61     public boolean cancel(final IImage image) {
     62         synchronized (mQueue) {
     63             int index = findItem(image);
     64             if (index >= 0) {
     65                 mQueue.remove(index);
     66                 return true;
     67             } else {
     68                 return false;
     69             }
     70         }
     71     }
     72 
     73     // The caller should hold mQueue lock.
     74     private int findItem(IImage image) {
     75         for (int i = 0; i < mQueue.size(); i++) {
     76             if (mQueue.get(i).mImage == image) {
     77                 return i;
     78             }
     79         }
     80         return -1;
     81     }
     82 
     83     // Clear the queue. Returns an array of tags that were in the queue.
     84     public int[] clearQueue() {
     85         synchronized (mQueue) {
     86             int n = mQueue.size();
     87             int[] tags = new int[n];
     88             for (int i = 0; i < n; i++) {
     89                 tags[i] = mQueue.get(i).mTag;
     90             }
     91             mQueue.clear();
     92             return tags;
     93         }
     94     }
     95 
     96     private static class WorkItem {
     97         IImage mImage;
     98         LoadedCallback mOnLoadedRunnable;
     99         int mTag;
    100 
    101         WorkItem(IImage image, LoadedCallback onLoadedRunnable, int tag) {
    102             mImage = image;
    103             mOnLoadedRunnable = onLoadedRunnable;
    104             mTag = tag;
    105         }
    106     }
    107 
    108     public ImageLoader(ContentResolver cr, Handler handler) {
    109         mCr = cr;
    110         start();
    111     }
    112 
    113     private class WorkerThread implements Runnable {
    114 
    115         // Pick off items on the queue, one by one, and compute their bitmap.
    116         // Place the resulting bitmap in the cache, then call back by executing
    117         // the given runnable so things can get updated appropriately.
    118         public void run() {
    119             while (true) {
    120                 WorkItem workItem = null;
    121                 synchronized (mQueue) {
    122                     if (mDone) {
    123                         break;
    124                     }
    125                     if (!mQueue.isEmpty()) {
    126                         workItem = mQueue.remove(0);
    127                     } else {
    128                         try {
    129                             mQueue.wait();
    130                         } catch (InterruptedException ex) {
    131                             // ignore the exception
    132                         }
    133                         continue;
    134                     }
    135                 }
    136 
    137                 final Bitmap b = workItem.mImage.miniThumbBitmap();
    138 
    139                 if (workItem.mOnLoadedRunnable != null) {
    140                     workItem.mOnLoadedRunnable.run(b);
    141                 }
    142             }
    143         }
    144     }
    145 
    146     private void start() {
    147         if (mDecodeThread != null) {
    148             return;
    149         }
    150 
    151         mDone = false;
    152         Thread t = new Thread(new WorkerThread());
    153         t.setName("image-loader");
    154         mDecodeThread = t;
    155         t.start();
    156     }
    157 
    158     public void stop() {
    159         synchronized (mQueue) {
    160             mDone = true;
    161             mQueue.notifyAll();
    162         }
    163         if (mDecodeThread != null) {
    164             try {
    165                 Thread t = mDecodeThread;
    166                 BitmapManager.instance().cancelThreadDecoding(t, mCr);
    167                 t.join();
    168                 mDecodeThread = null;
    169             } catch (InterruptedException ex) {
    170                 // so now what?
    171             }
    172         }
    173     }
    174 }
    175