android - AsyncTask: where does the return value of doInBackground() go?

Question

When calling AsyncTask<Integer,Integer,Boolean>, where is the return value of:

protected Boolean doInBackground(Integer... params)?

Usually we start AsyncTask with new AsyncTaskClassName().execute(param1,param2......); but it doesn't appear to return a value.

Where can the return value of doInBackground() be found?

Answer 1

The value is then available in onPostExecute which you may want to override in order to work with the result.

Here is example code snippet from Google's docs:

 private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
      protected Long doInBackground(URL... urls) {
          int count = urls.length;
          long totalSize = 0;
          for (int i = 0; i < count; i++) {
              totalSize += Downloader.downloadFile(urls[i]);
              publishProgress((int) ((i / (float) count) * 100));
          }
          return totalSize;
      }

      protected void onProgressUpdate(Integer... progress) {
          setProgressPercent(progress[0]);
      }

      protected void onPostExecute(Long result) {
          showDialog("Downloaded " + result + " bytes");
      }
 }