The method show() must be called from the User-Interface (UI) thread, while doInBackground() runs on different thread which is the main reason why AsyncTask was designed.
You have to call show() either in onProgressUpdate() or in onPostExecute().
For example:
class ExampleTask extends AsyncTask<String, String, String> {
// Your onPreExecute method.
@Override
protected String doInBackground(String... params) {
// Your code.
if (condition_is_true) {
this.publishProgress("Show the dialog");
}
return "Result";
}
@Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
connectionProgressDialog.dismiss();
downloadSpinnerProgressDialog.show();
}
}