App freezes after PreferenceSwitch in settings Android Studio

Question

I made settings activity from Android Studio, not manually. I want to make a switch that applies a dark mode in the app. The problem is that when I click the switch there is

Answer 1

Put this in your preferences.xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:app="http://schemas.android.com/apk/res-auto">
    <SwitchPreferenceCompat
        app:defaultValue="false"
        app:key="@string/key_night_mode"
        app:summaryOff="@string/summary_night_mode_off"
        app:summaryOn="@string/summary_night_mode_on"
        app:title="@string/title_night_mode" />
</PreferenceScreen>

Then in your SettingsFragment.java which extended PreferenceFragmentCompat inside the onCreatePreference() method:

    SwitchPreferenceCompat switchPreferenceCompat = findPreference(getString(R.string.key_night_mode));

    switchPreferenceCompat.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
                @Override
                public boolean onPreferenceChange(Preference preference, Object newValue) {
                    boolean isChecked = false;
                    if (newValue instanceof Boolean)
                        isChecked = (Boolean) newValue;
                    if (isChecked) {
                    //these lines so that the preference persists
getPreferenceManager().getSharedPreferences().edit().putBoolean(getString(R.string.key_night_mode), true).apply();
                    //you do not need to finish and recreate activity
                    //it takes care of any such things that needs to be done  
                    //automatically
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
                    } else {
                        getPreferenceManager().getSharedPreferences().edit().putBoolean(getString(R.string.key_night_mode), false).apply();
                        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
                    }
                    return true;
                }
            });

These lines of codes are working for me.

---

Note:

1. AppTheme should extends from Theme.AppCompat.DayNight or Theme.MaterialComponents.DayNight if you want to be dependent on platform for your night theme. Otherwise, you can create your separate Day and Night theme which extends from Theme.MaterialComponents.Light and Theme.MaterialComponents respectively(AppCompat has similar set of themes too).

2. Every time the app starts, it needs to respect the user's preferences and start in the user setted theme accordingly. To achieve this, you can check the preference and set theme in the MyApplication class as follows:

       SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
       boolean nightMode = sharedPreferences.getBoolean(getString(R.string.key_night_mode), false);
       if (nightMode)
           AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
       else {
           if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.P)
               AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
           else
               AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM);
       }