public void onClick(View v) {
  new Thread(new Runnable()) {
    public void run() {
      final Bitmap bitmap =
        loadImageFromNetwork("http://example.com/image.png");

        mImageView.post(new Runnable()) { //Handler
          public void run() {
            mImageView.setImageBitmap(b);
          }
        }
    }
  }
}

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) {
    mImageView.setImageBitmap(result);
  }
}