Android 에서 비동기 로 그림 불 러 오기

/**
 *       ，       ImageView   
*/
public class ImageDownloader extends AsyncTask<String, Integer, Object> {

  private static final String TAG = "ImageDownloader";
  //       ，        （            ，             ，   ListView     ）
  private Map<String, SoftReference<Drawable>> imageCache = new HashMap<String, SoftReference<Drawable>>();
  /**
   *        
   */
  private ImageView mImageView;

  public ImageDownloader(ImageView image) {
    mImageView = image;
  }

  @Override
  protected void onPreExecute() {
    super.onPreExecute();
  }

  @Override
  protected Object doInBackground(String... params) {
    // Log.i("ImageDownloader", "loading image...");
    String url = params[0];
    Drawable drawable = null;
    try {
      if (!"".equals(url) && url != null) {
        String fileName = url.hashCode()+".jpg";
        //               
        if (imageCache.containsKey(fileName)) {
          SoftReference<Drawable> softReference = imageCache.get(fileName);
          drawable = softReference.get();
          if (drawable != null) {
            return drawable;
          }
        }
        File dir = new File(FileConstant.IMAGE_FILE_PATH);
        if (!dir.exists()) {
          boolean m = dir.mkdirs();
        }
        File file = new File(dir, fileName);
        if (file.exists() && file.length() > 0) {
          Log.i(TAG, "load image from sd card");
          //            sdcard
          drawable = readFromSdcard(file);
        } else {
          //file.createNewFile();
          Log.i(TAG, "load image from network");
          URL imageUrl = new URL(url);
          //   sdcard
          if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            saveImageFile(imageUrl, file);
            drawable = Drawable.createFromStream(new FileInputStream(file), fileName);
          }else{
            //      
            drawable = Drawable.createFromStream(imageUrl.openStream(), fileName);
          }
        }
        if(drawable!=null){
          //      
          imageCache.put(fileName, new SoftReference<Drawable>(drawable));
        }
      }
    } catch (Exception e) {
      e.printStackTrace();
    } 
    return drawable;
  }
  /**
   * save image
*/
  private void saveImageFile(URL url, File file) {
    FileOutputStream out = null;
    InputStream in = null;
    try {
      file.deleteOnExit();
      out = new FileOutputStream(file);
      in = url.openStream();
      byte[] buf = new byte[1024];
      int len = -1;
      while((len = in.read(buf))!=-1){
        out.write(buf, 0, len);
        out.flush();
      }
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      if(out!=null){
        try {
          out.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if(in!=null){
        try {
          in.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }
  }

  /**
   *  sdcard     
 */
  private Drawable readFromSdcard(File file) throws Exception {
    FileInputStream in = new FileInputStream(file);
    return Drawable.createFromStream(in, file.getName());
  }

  @Override
  protected void onPostExecute(Object result) {
    super.onPostExecute(result);
    Drawable drawable = (Drawable) result;
    if (mImageView != null && drawable != null) {
      mImageView.setBackgroundDrawable(drawable);
    }
  }

  @Override
  protected void onProgressUpdate(Integer... values) {
    super.onProgressUpdate(values);
  }

  @Override
  protected void onCancelled() {
    super.onCancelled();
  }

}

public class ImageUtil {
  /**
   * image loader
   */
  static ImageDownloader2 loader = null;
  
  /**
   * load image
*/
  public static void loadImage(String url,final ImageView imageView){
    if(loader == null){
      loader = new ImageDownloader2();
    }
    loader.loadDrawable(url, new ImageCallback() {
      
      @Override
      public void imageLoaded(Drawable imageDrawable) {
        if(imageDrawable!=null){
          imageView.setBackgroundDrawable(imageDrawable);
        }
      }
    });
  }
  
}