1

In my application I have activity A.Upon clicking a button on this Activity, app launches Activity B.Inside Activity B's onCreate() I add a fragment.Everytime a fragment is created it loads a list from External Server using AsyncTask.

How can I persist this list on configuration changes?I have looked for many solutions but many suggest using 'android:configchanges' in manifest which I am totally against using.Many suggest and I have read about it also - to use setRetainInstance(true) in Fragment that would retain the fragment.

I have tried to implement it but I failed.Many tutorials after orientation changes check for the Fragment using findFragmentByTag but in my case it always returns null.Can anybody please post proper tutorial or proper answer on how to use RetainFragments?

Also I am calling AsyncTask to load list in onActivityCreated method in Fragment.According to android documentation when using setRetainInstance(true),onCreate(Bundle) will not be called since the fragment is not being re-created. onAttach(Activity) and onActivityCreated(Bundle) will still be called.

So should I call AsyncTask in onCreate Method?

akg
  • 670
  • 10
  • 30
  • 1
    Have a look at AsyncTaskLoader. These are made for exactly this situation you mention. – Michael Krause Nov 04 '14 at 22:50
  • Have you Saving and Restoring instance state? I think this question is simmilar to [http://stackoverflow.com/questions/6787071/android-fragment-how-to-save-states-of-views-in-a-fragment-when-another-fragmen?answertab=active#tab-top] – VizGhar Nov 04 '14 at 22:56
  • What is your app behaviour now ? – vovahost Nov 04 '14 at 23:08
  • When I rotate the device,Activity recreates hence fragment is created again.In fragment's onResume method I call execute() method of AsyncTask hence it again loads the list.But I have seen in many apps on screen rotation list does not load again. – akg Nov 04 '14 at 23:11
  • @vovahost - should I change the implementation? I want to continue using fragments though – akg Nov 04 '14 at 23:13
  • It's good practice to use fragments. Check the link in my answer. – vovahost Nov 04 '14 at 23:24

2 Answers2

2

I'm not sure if you remember this:

Caution: Your activity will be destroyed and recreated each time the user rotates the screen. When the screen changes orientation, the system destroys and recreates the foreground activity because the screen configuration has changed and your activity might need to load alternative resources (such as the layout).

I higly recommend you this post:
Handling Configuration Changes with Fragments
http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html

Note: In order for the Android system to restore the state of the views in your activity, each view must have a unique ID, supplied by the android:id attribute.

Source: http://developer.android.com/training/basics/activity-lifecycle/recreating.html

vovahost
  • 34,185
  • 17
  • 113
  • 116
1

Check this. This tutorial is for retaining MediaPlayer instance across orientation changes. its very straight forward. it used setRetainInstance(true) of fragment to retain MediaPlayer over orientation change.

This portion explains the callback of fragment fired during orientation chage

onAttach - always

onCreate - not on configuration change

onStart - always

onResume - always

onPause - always

onStop - always

onDestroy - not on configuration change

onDetach - always

So just Create a reference to your server response in this fragment and make call to server in onCreate.

You can use activity's isChangingConfigurations() method to know whether fragment's life cycle is called because of orientation changes or fragment is being destroyed if you want to release some resources.

In activity use FragmentManager to check whether there is an instance of the fragment already exists, if not create new one and add it.

Ankit
  • 270
  • 1
  • 4
  • 12