android 图片缓存

图片缓存的主要三步骤：

一、从缓存中获取图片

二、如果缓存中未获取图片，则从存储卡中获取

三、如果存储卡中未获取图片，则从网络中获取

public class ImageCache{

    private static final String TAG = "ImageCache";
    private ExecutorService mThreadPool;
    //写个单例模式
   private static ImagCache mInstance;
   public synchronized static ImageCache getInstance(){
     if(mInstance == null) mInstance = new ImageCache;
         return mInstance;
    
  }
  private Image(){
        int maxSize = (int)(Runtime.getRuntime().maxMemory()/8);
        mLruCache = new LruCache<String, Bitmap>(maxSize){
            @Override
            protected int sizeOf(String key, Bitmap value) {
                if(value !=null){
                    return value.getRowBytes()*value.getHeight();
                }
                return 0;
                
            }
        };
      mThreadPool = Executors.newFixedThreadPool(5);
}
 
  //获取图片格式
    private String getImagrType(String url){
        String[] split = url.split("\.");
        return split[split.length-1];
    }
    
    //从缓存中获取图片
    private Bitmap getBitmapFromCache(String url){
        android.util.Log.d(TAG, "load from cache.....");
        return mLruCache.get(url);
    }
    
    //从磁盘中获取图片
    private Bitmap getBitmapFromDisk(String url){
        android.util.Log.d(TAG, "load from disk....");
        return BitmapFactory.decodeFile(getCacheDir()+url);
    }
    
    //将图片加入缓存
    private void addToLru(final String url,Bitmap bitmap){
        if(  getBitmapFromCache(url) != null) return ;
        android.util.Log.d(TAG, "add to Lru...");
         mLruCache.put(url, bitmap);
    }
    //将图片写入磁盘
    private void addToDisk(String url,Bitmap bitmap,String type) throws IOException{
        if(getBitmapFromDisk(url) != null) return;
        android.util.Log.d(TAG, "add to disk.....");
        FileOutputStream stream = new FileOutputStream(getCacheDir()+url);
        if(type.equalsIgnoreCase("png")){
            bitmap.compress(CompressFormat.PNG, 100, stream);
        }else{
            bitmap.compress(CompressFormat.JPEG, 100, stream);
        }
        stream.close();
        addToLru(url, bitmap);
    }
    
    //获取磁盘缓存路径
    private static String getCacheDir(){
        String dir = null;
        
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            dir = Environment.getExternalStorageDirectory()+File.separator+"Matrial"+File.separator
                    +"image"+File.separator;
        }else{
            dir = App.context.getCacheDir()+File.separator+"image"+File.separator;
        }
        
        return mkdir(dir);
    }    
    
    private static String mkdir(String dir){
        File file =new File(dir);
        if(!file.exists()){
            file.mkdirs();
        }    
        return dir;
    }

//网络下载图片

public void load(final String url, final OnImageLoadedListener l) {
final Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case Constants.SUCCESS:
if(l != null) l.onImage((Bitmap) msg.obj);
break;
case Constants.FAILED:
if(l != null) l.onImage(null);
break;
}
}
};


final String key = Encrypt.md5(url);
Bitmap bmp = loadByLru(key);

if(bmp != null) {
handler.obtainMessage(Constants.SUCCESS, bmp).sendToTarget();
return;
}

bmp = loadByDisk(key);
if(bmp != null) {
handler.obtainMessage(Constants.SUCCESS, bmp).sendToTarget();
return;
}

mThreadPool.execute(new Runnable() {
@Override
public void run() {
DefaultHttpClient client = null;
try {
System.out.println("get by network.........................................");
client = new DefaultHttpClient();
HttpGet get = new HttpGet(url);
HttpResponse response = client.execute(get);
if(response.getStatusLine().getStatusCode() == 200) {
InputStream stream = response.getEntity().getContent();
Bitmap b = BitmapFactory.decodeStream(stream);
stream.close();
addToDisk(key, b, getImageType(url));
handler.obtainMessage(Constants.SUCCESS, b).sendToTarget();
return;
}

throw new Exception();
} catch (Exception e) {
} finally {
if(client != null) client.getConnectionManager().shutdown();
}
}
});
}

  


//接口回调

    public interface OnImageLoadedListener {
       public void onImage(Bitmap bmp);
   }

}