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POAndroid Fragments. Retaining an AsyncTask during screen rotation or configuration change
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copied!<p>I'm working on a Smartphone / Tablet app, using only one APK, and loading resources as is needed depending on screen size, the best design choice seemed to be using Fragments via the ACL.</p> <p>This app has been working fine until now being only activity based. This is a mock class of how I handle AsyncTasks and ProgressDialogs in the Activities in order to have them work even when the screen is rotated or a configuration change occurs mid communication.</p> <p>I will not change the manifest to avoid recreation of the Activity, there are many reasons why I dont want to do it, but mainly because the official docs say it isnt recomended and I've managed without it this far, so please dont recomend that route.</p> <pre><code>public class Login extends Activity { static ProgressDialog pd; AsyncTask<String, Void, Boolean> asyncLoginThread; @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.login); //SETUP UI OBJECTS restoreAsyncTask(); } @Override public Object onRetainNonConfigurationInstance() { if (pd != null) pd.dismiss(); if (asyncLoginThread != null) return (asyncLoginThread); return super.onRetainNonConfigurationInstance(); } private void restoreAsyncTask();() { pd = new ProgressDialog(Login.this); if (getLastNonConfigurationInstance() != null) { asyncLoginThread = (AsyncTask<String, Void, Boolean>) getLastNonConfigurationInstance(); if (asyncLoginThread != null) { if (!(asyncLoginThread.getStatus() .equals(AsyncTask.Status.FINISHED))) { showProgressDialog(); } } } } public class LoginThread extends AsyncTask<String, Void, Boolean> { @Override protected Boolean doInBackground(String... args) { try { //Connect to WS, recieve a JSON/XML Response //Place it somewhere I can use it. } catch (Exception e) { return true; } return true; } protected void onPostExecute(Boolean result) { if (result) { pd.dismiss(); //Handle the response. Either deny entry or launch new Login Succesful Activity } } } } </code></pre> <p>This code is working fine, I have around 10.000 users without complaint, so it seemed logical to just copy this logic into the new Fragment Based Design, but, of course, it isnt working.</p> <p>Here is the LoginFragment:</p> <pre><code>public class LoginFragment extends Fragment { FragmentActivity parentActivity; static ProgressDialog pd; AsyncTask<String, Void, Boolean> asyncLoginThread; public interface OnLoginSuccessfulListener { public void onLoginSuccessful(GlobalContainer globalContainer); } public void onSaveInstanceState(Bundle outState){ super.onSaveInstanceState(outState); //Save some stuff for the UI State } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setRetainInstance(true); //If I setRetainInstance(true), savedInstanceState is always null. Besides that, when loading UI State, a NPE is thrown when looking for UI Objects. parentActivity = getActivity(); } @Override public void onAttach(Activity activity) { super.onAttach(activity); try { loginSuccessfulListener = (OnLoginSuccessfulListener) activity; } catch (ClassCastException e) { throw new ClassCastException(activity.toString() + " must implement OnLoginSuccessfulListener"); } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { RelativeLayout loginLayout = (RelativeLayout) inflater.inflate(R.layout.login, container, false); return loginLayout; } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); //SETUP UI OBJECTS if(savedInstanceState != null){ //Reload UI state. Im doing this properly, keeping the content of the UI objects, not the object it self to avoid memory leaks. } } public class LoginThread extends AsyncTask<String, Void, Boolean> { @Override protected Boolean doInBackground(String... args) { try { //Connect to WS, recieve a JSON/XML Response //Place it somewhere I can use it. } catch (Exception e) { return true; } return true; } protected void onPostExecute(Boolean result) { if (result) { pd.dismiss(); //Handle the response. Either deny entry or launch new Login Succesful Activity } } } } } </code></pre> <p>I cant use <code>onRetainNonConfigurationInstance()</code> since it has to be called from the Activity and not the Fragment, same goes with <code>getLastNonConfigurationInstance()</code>. I've read some similar questions here with no answer.</p> <p>I understand that it might require some working around to get this stuff organized properly in fragments, that being said, I would like to maintain the same basic design logic.</p> <p><strong>What would be the proper way to retain the AsyncTask during a configuration change, and if its still runing, show a progressDialog, taking into consideration that the AsyncTask is a inner class to the Fragment and it is the Fragment itself who invokes the AsyncTask.execute()?</strong></p>

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