How setRetainInstance(true) affect lifecycle of Fragment

Anonymous

12:07

It's part of the articles of lifecycle: start reading from Understand lifecycle of Activity and Fragment, Introduction.

The Fragment.setRetainInstance() method control whether a fragment instance is retained across Activity re-creation (such as from a configuration change). This can only be used with fragments not in the back stack. If set, the fragment lifecycle will be slightly different when an activity is recreated:

onDestroy() will not be called (but onDetach() still will be, because the fragment is being detached from its current activity).
onCreate(Bundle) will not be called since the fragment is not being re-created.
onAttach(Activity) and onActivityCreated(Bundle) will still be called.

~ reference: http://developer.android.com/reference/android/app/Fragment.html#setRetainInstance(boolean)

Refer to the last exercise, "UI elements lost after Activity/Fragment re-created". Consider the image_c, it is loaded in onCreateView(), only if savedInstanceState == null. Without setRetainInstance(true), it will not be loaded after orientation changed, because savedInstanceState != null.

image_c lost after orientation changed, without setRetainInstance(true)

MYTAG LogCat listed here:

Orientation changed:

MainActivity.onPause
MyFragment1.onPause
MainActivity.onStop
MyFragment1.onStop
MainActivity.onDestroy
MyFragment1.onDestroyView
MyFragment1.onDestroy
MyFragment1.onDetach
MainActivity.onCreate / savedInstanceState != null
MyFragment1.onAttach
MyFragment1.onCreate / savedInstanceState != null
MainActivity.onStart
MyFragment1.onCreateView / savedInstanceState != null
MyFragment1.onActivityCreated / savedInstanceState != null
MyFragment1.onStart
MainActivity.onResume
MyFragment1.onResume

To know how setRetainInstance(true) affect lifecycle of Fragment, modify MyFragment.java from last exercise "UI elements lost after Activity/Fragment re-created", override onActivityCreated() method to call setRetainInstance(true).

 @Override
 public void onActivityCreated(Bundle savedInstanceState) {
  recLifeCycle_with_savedInstanceState(savedInstanceState);
  super.onActivityCreated(savedInstanceState);
  
  setRetainInstance(true);
 }