java - InputStream 在 Android 上冻结 UI

Question

我正在后台下载图像以获取列表。我注意到即使AsycTask滚动也不流畅。经过几个小时的调试，我得出结论，这InputStream是有罪的。

doInBackground应该在非 ui 线程上工作，那么为什么它会影响 UI？如果我注释掉InputStream代码，滚动是平滑的。

我连续有 3 张图片，所以通常会同时加载 3 张图片。

class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
    final WeakReference<ImageView> imageViewReference;

    public BitmapWorkerTask(ImageView imageView) {
        // Use a WeakReference to ensure the ImageView can be garbage collected
        imageViewReference = new WeakReference<ImageView>(imageView);
    }


    // Decode image in background.
    @Override
    protected Bitmap doInBackground(String... params) {

        InputStream is = null;

         try {
             is = (InputStream) new URL(params[0]).getContent();
         } catch (MalformedURLException e) {
            e.printStackTrace();
         } catch (IOException e) {
            e.printStackTrace();
         }


        return null;

    }


    // Once complete, see if ImageView is still around and set bitmap.
    @Override
    protected void onPostExecute(Bitmap bitmap) {
        // REMOVED ON PURPOSE TO CONFIRM THAT INPUTSTREAM IS GUILTY
    }

}