Android – save/restore fragment state

When a fragment is moved to the backstack, it isn’t destroyed. All the instance variables remain there. So this is the place to save your data. In onActivityCreated you check the following conditions:

1. Is the bundle != null? If yes, that’s where the data is saved (probably orientation change).
2. Is there data saved in instance variables? If yes, restore your state from them (or maybe do nothing, because everything is as it should be).
3. Otherwise your fragment is shown for the first time, create everything anew.

Edit: Here’s an example

public class ExampleFragment extends Fragment {
    private List<String> myData;

    @Override
    public void onSaveInstanceState(final Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putSerializable("list", (Serializable) myData);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        if (savedInstanceState != null) {
            //probably orientation change
            myData = (List<String>) savedInstanceState.getSerializable("list");
        } else {
            if (myData != null) {
                //returning from backstack, data is fine, do nothing
            } else {
                //newly created, compute data
                myData = computeData();
            }
        }
    }
}