PreferenceFragment中的PreferenceScreen在ScreenOrientation更改时关闭

Question

I got some nested PreferenceScreen in my PreferenceActivity , and under them a series of CheckBoxPreference .

Everything is working well but, whenever the device is rotated, the PreferenceActivity returns to the main PreferenceScreen , disregarding what nested preference screen the user was in.

This is exactly like in these previous SO questions, where the solution was to add a key to the PreferenceScreen:

1. When my PreferenceActivity rotates, it does not remember which PreferenceScreen was open

2. How to prevent quitting from inner preference screen when there's a configuration change

3. Nested Preference Screen closes on Screenorientation change in Android

I've added keys to all my PreferenceScreen and the solution works, as long as I use the deprecated way:

public class Settings extends PreferenceActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.prefs);
    }
}

The problem is I'm using a PreferenceFragment , like in this SO answer (and also here ).

The code:

public class Settings extends PreferenceActivity {

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    getFragmentManager().
            beginTransaction().
            replace(android.R.id.content, new MyPreferenceFragment()).
            commit();
}

    public static class MyPreferenceFragment extends PreferenceFragment
    {
        @Override
        public void onCreate(final Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            addPreferencesFromResource(R.xml.prefs);
        }
    }
}

So, how to keep inner PreferenceScreen open after screen orientation changes, if possible with the current code?

I see that for Preferences Google now recommends AppCompatActivity and PreferenceFragmentCompat, but I would prefer to not use any libraries, not even Google's, specially for only such a small detail.

Answer 1

I'm quite surprised this little problem managed to generate three SO questions while Android was under API 11, and none - that I can find at least - between API 11 and API 28, when PreferenceFragment was deprecated.

Anyways, I found the solution here in SO as well, in an answer to Android- deprecated method warning regarding PreferenceActivity .

The key is to check if (savedInstanceState == null) before adding the PreferenceFragment , like this:

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    if (savedInstanceState == null)
        getFragmentManager().
                beginTransaction().
                replace(android.R.id.content, new MyPreferenceFragment()).
                commit();
}

Now the nested PreferenceScreen remains open when screen orientation changes, as long as it has an android:key value set in, of course.