在这种情况下，如何在安卓中清除图像视图

Question

private static class ViewHolder {
     ImageView imageView;
     TextView region;
     TextView area;
     TextView id;
     TextView shop_name;
     public String imageURL;
     public Bitmap bitmap;
}
@Override
public View getView(int arg0, View arg1, ViewGroup arg2) {
    // TODO
    ViewHolder viewHolder = null;
    if (arg1 == null) {
        arg1 = myInflater.inflate(R.layout.details, arg2, false);
        viewHolder = new ViewHolder();
        viewHolder.imageView = (ImageView) arg1.findViewById(R.id.imageView1);
        viewHolder.region = (TextView) arg1.findViewById(R.id.textView1);
        viewHolder.area = (TextView) arg1.findViewById(R.id.textView2);
        viewHolder.id = (TextView) arg1.findViewById(R.id.textView3);
        viewHolder.shop_name = (TextView) arg1.findViewById(R.id.textView4);
        arg1.setTag(viewHolder);
    }
    viewHolder = (ViewHolder)arg1.getTag();
    viewHolder.imageView.setImageResource(R.drawable.loading);
    ShopEntry entry = getItem(arg0);
    viewHolder.imageURL = entry.image_url;
    viewHolder.region.setText(entry.region);
    viewHolder.area.setText(entry.area);
    viewHolder.id.setText(entry.id);
    viewHolder.shop_name.setText(entry.shop_name);
    new DownloadAsyncTask().execute(viewHolder);
    return arg1;
}
private class DownloadAsyncTask extends AsyncTask<ViewHolder, Void, ViewHolder> {   
    @Override
    protected ViewHolder doInBackground(ViewHolder... params) {
        // TODO Auto-generated method stub
        //load image directly
        ViewHolder viewHolder = params[0];
        try {
            URL imageURL = new URL(viewHolder.imageURL);
            viewHolder.bitmap = BitmapFactory.decodeStream(imageURL.openStream());
        } catch (IOException e) {
            // TODO: handle exception
            Log.e("test", "Downloading Image Failed");
            viewHolder.bitmap = null;
        }
        return viewHolder;
    }
    @Override
    protected void onPostExecute(ViewHolder result) {
        // TODO Auto-generated method stub
        if (result.bitmap == null) {
            result.imageView.setImageResource(R.drawable.loading);
        } else {
            result.imageView.setImageBitmap(result.bitmap);
        }
    }
}

在上面的代码中，我已经在列表视图自定义适配器上实现了异步任务。问题是，当图像重新加载时，它被替换旧图像，而不是清除旧图像再重新加载新图像，因此显示顺序不正确。

我把

viewHolder.imageView.setImageResource(R.drawable.loading); 

在 getView(( 适配器内部，但它似乎没有按预期工作，如何解决？谢谢

Answer 1

异步任务下载图像时，适配器可能会回收视图持有者，因此异步任务会将错误的图像设置为视图持有者实例。

您需要注意异步任务将位图分配给有效的视图持有者，而不是过时的视图持有者。