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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，它会替换旧图像，而不是清除旧图像然后重新加载新图像，因此显示顺序不正确。

我放了

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

在 getview() 适配器内部，但似乎无法按预期工作，如何解决？谢谢

4

1 回答 1

1

当您的异步任务下载图像时，适配器可能会回收视图持有者，因此异步任务将为视图持有者实例设置错误的图像。

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。

于 2013-07-30T06:26:07.537 回答