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.
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.
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);
}
LogCat in Orientation Changed:
- MainActivity.onPause
- MyFragment1.onPause
- MainActivity.onStop
- MyFragment1.onStop
- MainActivity.onDestroy
- MyFragment1.onDestroyView
- MyFragment1.onDetach
- MainActivity.onCreate / savedInstanceState != null
- MyFragment1.onAttach
- MainActivity.onStart
- MyFragment1.onCreateView / savedInstanceState == null
- MyFragment1.onActivityCreated / savedInstanceState == null
- MyFragment1.onStart
- MainActivity.onResume
- MyFragment1.onResume
Download the files.
* the original chart of fragment lifecycle is taken here.
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