android端读取本地图片出现OutOfMemoryException解决办法

前些日子一直为图片内存溢出问题困扰着，查了N多资料，将google彻底翻遍了都没找到解决方案，就当我几乎绝望的时候意外发现了一位网友的一个工具类，抱着最后一丝希望将代码co过来试了一把，结果令我喜出望外。嘿，解决了！暂不说多么欢喜了，听我慢慢道来这其中的前因后果吧！

   需求：下载时候将图片一并down下来，在空间里显示并支持离线观看

   第一个版本代码：

   //从本地读取图片
    public Bitmap getBitmapFromSD(String filename) {
        FileInputStream fi = null;
        BufferedInputStream bi = null;
        Bitmap bp = null;
        try {
            fi = new FileInputStream(filename);
            bi = new BufferedInputStream(fi);
            bp = BitmapFactory.decodeStream(bi);
        } catch (IOException e) {
            bp = null;
        } finally {
            try {
                if (bi != null) {
                    bi.close();
                }
                if (fi != null) {
                    fi.close();
                }
            } catch (IOException e) {
                bp = null;
            }
        }
        return bp;
    }

public final class BitMapUtil {
      private static final Size ZERO_SIZE = new Size(0, 0);
      private static final Options OPTIONS_GET_SIZE = new Options();
      private static final Options OPTIONS_DECODE = new Options();
      private static final byte[] LOCKED = new byte[0];
// 此对象用来保持Bitmap的回收顺序,保证最后使用的图片被回收
      private static final LinkedList CACHE_ENTRIES = new LinkedList(); 
// 线程请求创建图片的队列
     private static final Queue TASK_QUEUE = new LinkedList(); 
// 保存队列中正在处理的图片的key,有效防止重复添加到请求创建队列 
     private static final Set TASK_QUEUE_INDEX = new HashSet();  
// 缓存Bitmap
     private static final Map IMG_CACHE_INDEX = new HashMap();                         // 通过图片路径,图片大小
     private static int CACHE_SIZE = 20; // 缓存图片数量
   static {
     OPTIONS_GET_SIZE.inJustDecodeBounds = true;
  // 初始化创建图片线程,并等待处理
  new Thread() {
   {
    setDaemon(true);
   }
   public void run() {
    while (true) {
     synchronized (TASK_QUEUE) {
      if (TASK_QUEUE.isEmpty()) {
       try {
        TASK_QUEUE.wait();
       } catch (InterruptedException e) {
        e.printStackTrace();
       }
      }
     }
     QueueEntry entry = TASK_QUEUE.poll();
     String key = createKey(entry.path, entry.width,
       entry.height);
     TASK_QUEUE_INDEX.remove(key);
     createBitmap(entry.path, entry.width, entry.height);
    }
   }
  }.start();
 }
 
 
 public static Bitmap getBitmap(String path, int width, int height) {
        if(path==null){
            return null;
        }
  Bitmap bitMap = null;
  try {
   if (CACHE_ENTRIES.size() >= CACHE_SIZE) {
    destoryLast();
   }
   bitMap = useBitmap(path, width, height);
   if (bitMap != null && !bitMap.isRecycled()) {
    return bitMap;
   }
   bitMap = createBitmap(path, width, height);
   String key = createKey(path, width, height);
   synchronized (LOCKED) {
    IMG_CACHE_INDEX.put(key, bitMap);
    CACHE_ENTRIES.addFirst(key);
   }
  } catch (OutOfMemoryError err) {
   destoryLast();
   System.out.println(CACHE_SIZE);
   return createBitmap(path, width, height);
  }
  return bitMap;
 }
 
 
 public static Size getBitMapSize(String path) {
  File file = new File(path);
  if (file.exists()) {
   InputStream in = null;
   try {
    in = new FileInputStream(file);
    BitmapFactory.decodeStream(in, null, OPTIONS_GET_SIZE);
    return new Size(OPTIONS_GET_SIZE.outWidth,
      OPTIONS_GET_SIZE.outHeight);
   } catch (FileNotFoundException e) {
    return ZERO_SIZE;
   } finally {
    closeInputStream(in);
   }
  }
  return ZERO_SIZE;
 }
 
 // ------------------------------------------------------------------ private Methods
 // 将图片加入队列头
 private static Bitmap useBitmap(String path, int width, int height) {
  Bitmap bitMap = null;
  String key = createKey(path, width, height);
  synchronized (LOCKED) {
   bitMap = IMG_CACHE_INDEX.get(key);
   if (null != bitMap) {
    if (CACHE_ENTRIES.remove(key)) {
     CACHE_ENTRIES.addFirst(key);
    }
   }
  }
  return bitMap;
 }
 
 // 回收最后一张图片
 private static void destoryLast() {
  synchronized (LOCKED) {
   String key = CACHE_ENTRIES.removeLast();
   if (key.length() > 0) {
    Bitmap bitMap = IMG_CACHE_INDEX.remove(key);
    if (bitMap != null && !bitMap.isRecycled()) {
     bitMap.recycle();
     bitMap = null;
    }
   }
  }
 }
 
 // 创建键
 private static String createKey(String path, int width, int height) {
  if (null == path || path.length() == 0) {
   return "";
  }
  return path + "_" + width + "_" + height;
 }
 
 // 通过图片路径,宽度高度创建一个Bitmap对象
 private static Bitmap createBitmap(String path, int width, int height) {
  File file = new File(path);
  if (file.exists()) {
   InputStream in = null;
   try {
    in = new FileInputStream(file);
    Size size = getBitMapSize(path);
    if (size.equals(ZERO_SIZE)) {
     return null;
    }
    int scale = 1;
    int a = size.getWidth() / width;
    int b = size.getHeight() / height;
    scale = Math.max(a, b);
    synchronized (OPTIONS_DECODE) {
     OPTIONS_DECODE.inSampleSize = scale;
     Bitmap bitMap = BitmapFactory.decodeStream(in, null,
       OPTIONS_DECODE);
     return bitMap;
    }
   } catch (FileNotFoundException e) {
                Log.v("BitMapUtil","createBitmap=="+e.toString());
   } finally {
    closeInputStream(in);
   }
  }
  return null;
 }
 
 // 关闭输入流
 private static void closeInputStream(InputStream in) {
  if (null != in) {
   try {
    in.close();
   } catch (IOException e) {
    Log.v("BitMapUtil","closeInputStream=="+e.toString());
   }
  }
 }
 
 // 图片大小
 static class Size {
  private int width, height;
  Size(int width, int height) {
   this.width = width;
   this.height = height;
  }
  public int getWidth() {
   return width;
  }
  public int getHeight() {
   return height;
  }
 }
 
 // 队列缓存参数对象
 static class QueueEntry {
  public String path;
  public int width;
  public int height;
 }
}
 

   在使用时我只调用了getBitmap方法，将需要设置的高度宽度以及本地图片路径传递过去就能自动返回bitmap给我，而且当捕捉到OOMError的时候将LinkedList的最后一张图片也就是最先存的图片进行溢出并回收就大功告成，特别注意的是这里捕捉错误Exception是获取不到的，一定要手动捕获OutOfMemoryError你才能进行处理（估计这些道理大家都懂得，所以不赘述啦，童鞋们加油！办法总比困难多o(∩_∩)o ）