@Override
public View getView ( int position , View convertView , ViewGroup parent ) {
  ViewHolder holder ;
  if ( convertView == null ) {
   convertView = inflater . inflate ( R . layout . list_item , null ) ;
   holder = new ViewHolder ( ) ;
   ……
   convertView . setTag ( holder ) ;
  } else {
   holder = ( ViewHolder ) convertView . getTag ( ) ;
  }
}

/**
  * 显示这个图片,解决了列表问题.
  * 列表问题：滑动过程中，getView的imageView会重复利用，导致图片会串位
  * @param imageView 显得的View
  * @param url the url
  * @return
  */
  public void display( final ImageView imageView,String url) {
   if (AbStrUtil.isEmpty(url)){
    if (noImage != null ){
     if (loadingView != null ){
      loadingView.setVisibility(View.INVISIBLE);
      imageView.setVisibility(View.VISIBLE);
     }
     imageView.setImageDrawable(noImage);
    }
    return ;
   }
   //设置下载项
   final AbImageDownloadItem item = new AbImageDownloadItem();
   //设置显示的大小
   item.width = width;
   item.height = height;
   //设置为缩放
   item.type = type;
   item.imageUrl = url;
   final String cacheKey = AbImageCache
   .getCacheKey(item.imageUrl, item.width, item.height, item.type);
   item.bitmap = AbImageCache.getBitmapFromCache(cacheKey);
   //if(D) Log.d(TAG, "缓存中获取的"+cacheKey+":"+item.bitmap);
   //设置标记
   imageView.setTag(url);
   if (item.bitmap == null ){
    //先显示加载中
    if (loadingView!= null ){
     loadingView.setVisibility(View.VISIBLE);
     imageView.setVisibility(View.INVISIBLE);
    } else if (loadingImage != null ){
     imageView.setImageDrawable(loadingImage);
    }
    //下载完成后更新界面
    item.setListener( new AbImageDownloadListener() {
     @Override
     public void update(Bitmap bitmap, String imageUrl) {
      //未设置加载中的图片，并且设置了隐藏的View
      if (loadingView != null && imageUrl.equals(imageView.getTag())){
       loadingView.setVisibility(View.INVISIBLE);
       imageView.setVisibility(View.VISIBLE);
      }
      //要判断这个imageView的url有变化，如果没有变化才set，
      //有变化就取消，解决列表的重复利用View的问题
      if(bitmap!=null&& imageUrl.equals(imageView.getTag())){
       if (D) Log.d(TAG, "图片下载，设置:" +imageUrl);
       imageView.setImageBitmap(bitmap);
      } else {
       if (errorImage != null && imageUrl.equals(imageView.getTag())){
        imageView.setImageDrawable(errorImage);
       }
      }
     }
    });
    if (D) Log.d(TAG, "图片下载，执行:" +url);
    mAbImageDownloadPool.execute(item);
   } else {
    if (loadingView != null ){
     loadingView.setVisibility(View.INVISIBLE);
     imageView.setVisibility(View.VISIBLE);
    }
    imageView.setImageBitmap(item.bitmap);
   }
  }