Async task android onPostExecute

Question

In my android application i use AsyncTask to download the image from internet.

I pass the url and my AsyncTask does the download. But how do i return the bitmap back to my activity. Currently i pass the callback function to my asynctask constructor and in the OnPostExecute i invoke the callback function. Is this the correct way to do it.

Answer 1

You can do something like this:

public Bitmap btm;
public void onClick(View v) {
  new DownloadImageTask().execute("http://example.com/image.png");
}

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
     protected Bitmap doInBackground(String... urls) {
         return loadImageFromNetwork(urls[0]);
     }

     protected void onPostExecute(Bitmap result) {
         // set image for ImageView
         mImageView.setImageBitmap(result);
         // orsimply save it
         btm = result;
     }
 }

Answer 2

The result you return from doInBackground is passed to onPostExecute so simple return the bitmap from doInBackground method and handle it in onPostExecute.