setDefaultNightMode() only works after second call in PreferenceFragment

Question

I am working to implement a dark mode into my app. Right now I try to switch the UI mode between light and dark using a PreferenceFragment nested inside an AppCompatActivity. The App behaves like this, starting from the light theme as a default value:

• If I select 'dark' in the ListPreference, the summary of the preference changes, but the UI stays light in this and all the other activities.
• If I select 'dark' a second time, the activity switches to dark theme, as well as the other activities in the backstack.
• The same thing happens in reverse, when I want to switch back to the light theme.

So basically everything works, but you have to select the desired value in the ListPreference twice. The code for the ListPreference:

final Preference listPreferenceDesign = findPreference(PREF_DESIGN);
listPreferenceDesign.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
    @Override
    public boolean onPreferenceChange(Preference preference, Object o) {
            if (((ListPreference) preference).getValue().equals("light")) {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
            } else if (((ListPreference) preference).getValue().equals("dark")) {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
            }
            return true;
    }
});

What I tried so far:

• Call getActivity.recreate()before the return true; statement
• Call getActivity.recreate()after a short delay using a Handler
• Call this.recreate() in the onResume() method of the parent Activity when a boolean changedDesignSetting was true

I am thankful for further help.

Answer 1

I finally get it to work using an OnSharedPreferenceChangeListener in the parent activity. Now the code in the parent activity goes like this:

getFragmentManager().beginTransaction().replace(R.id.settingsPlaceholderID, preferenceFragment).commit();
SharedPreferences.OnSharedPreferenceChangeListener sharedPreferenceChangeListener = new SharedPreferences.OnSharedPreferenceChangeListener() {
    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        if (key.equals(PREF_DESIGN)) {
            if (sharedPreferences.getString(key, "light").equals("light")) {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
            } else {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
            }
        }
    }
};

SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
sharedPreferences.registerOnSharedPreferenceChangeListener(sharedPreferenceChangeListener);

And in the PreferenceFragment I only have:

final Preference listPreferenceDesign = findPreference(PREF_DESIGN);
listPreferenceDesign.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
    @Override
    public boolean onPreferenceChange(Preference preference, Object o) {           
        return true;
    }
});