Cardboard sample, method must be called from UI thread

Question

Trying to develop an app for google cardboard, i downloaded the sample from the official sdk. In the inner class ImageLoaderTask ( which it should be the helper class to manage threading )

    class ImageLoaderTask extends AsyncTask<Pair<Uri, Options>, Void, Boolean> {

    /**
     * Reads the bitmap from disk in the background and waits until it's loaded by pano widget.
     */
    @Override
    protected Boolean doInBackground(Pair<Uri, Options>... fileInformation) {
      Options panoOptions = null;  // It's safe to use null VrPanoramaView.Options.
      InputStream istr = null;
      if (fileInformation == null || fileInformation.length < 1
          || fileInformation[0] == null || fileInformation[0].first == null) {
        AssetManager assetManager = getAssets();
        try {
          istr = assetManager.open("andes.jpg");
          panoOptions = new Options();
          panoOptions.inputType = Options.TYPE_STEREO_OVER_UNDER;
        } catch (IOException e) {
          Log.e(TAG, "Could not decode default bitmap: " + e);
          return false;
        }
      } else {
        try {
          istr = new FileInputStream(new File(fileInformation[0].first.getPath()));
          panoOptions = fileInformation[0].second;
        } catch (IOException e) {
          Log.e(TAG, "Could not load file: " + e);
          return false;
        }
      }

      panoWidgetView.loadImageFromBitmap(BitmapFactory.decodeStream(istr), panoOptions);
      try {
        istr.close();
      } catch (IOException e) {
        Log.e(TAG, "Could not close input stream: " + e);
      }

      return true;
    }
  }

panoWidgetView is the widget for the panorama, and it is declared inside the activity which includes this inner class. But Android Studio gives me this error: Method loadImageFromBitmap must be called from the UI thread, currently inferred thread is worker. Any possible solution?

Answer 1

try moving "loadImageFromBitmap" inside onPostExecute :

class ImageLoaderTask extends AsyncTask<Pair<Uri, BitmapFactory.Options>, Void, Boolean> {
        Options panoOptions = null;  // It's safe to use null VrPanoramaView.Options.
        InputStream istr = null;

        /**
         * Reads the bitmap from disk in the background and waits until it's loaded by pano widget.
         */
        @Override
        protected Boolean doInBackground(Pair<Uri, BitmapFactory.Options>... fileInformation) {

            if (fileInformation == null || fileInformation.length < 1
                    || fileInformation[0] == null || fileInformation[0].first == null) {
                AssetManager assetManager = getAssets();
                try {
                    istr = assetManager.open("andes.jpg");
                    panoOptions = new Options();
                    panoOptions.inputType = Options.TYPE_STEREO_OVER_UNDER;
                } catch (IOException e) {
                    Log.e(TAG, "Could not decode default bitmap: " + e);
                    return false;
                }
            } else {
                try {
                    istr = new FileInputStream(new File(fileInformation[0].first.getPath()));
                    panoOptions = fileInformation[0].second;
                } catch (IOException e) {
                    Log.e(TAG, "Could not load file: " + e);
                    return false;
                }
            }

            try {
                istr.close();
            } catch (IOException e) {
                Log.e(TAG, "Could not close input stream: " + e);
            }

            return true;
        }

        @Override
        protected void onPostExecute(Boolean aBoolean) {
            if( istr!=null && panoOptions!=null){
                 panoWidgetView.loadImageFromBitmap(BitmapFactory.decodeStream(istr), panoOptions);
            }
            super.onPostExecute(aBoolean);
        }
    }