How can you update Day Night Mode Instantly in PreferenceFragment?

问题

I've seen some apps like Pocket that can toggle between Day and Night mode in the settings instantly without reloading, but I'm not able to do that in my own example:

public class SettingsActivity extends PreferenceActivity {
    @Override
    public void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getFragmentManager().beginTransaction().replace(android.R.id.content, new PrefsFragment()).commit();
    }

    public static class PrefsFragment extends PreferenceFragment{
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            final Context context = getActivity();
            addPreferencesFromResource(R.xml.preferences);
            SwitchPreference dayNightSwitch = (SwitchPreference) findPreference(getString(R.string.pref_day_night_key));
            dayNightSwitch.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
                @Override
                public boolean onPreferenceChange(Preference preference, Object newValue) {
                    boolean isNightMode = (boolean) newValue;    
                    AppCompatDelegate.setDefaultNightMode(isNightMode? AppCompatDelegate.MODE_NIGHT_YES:AppCompatDelegate.MODE_NIGHT_NO);
                    return true;
                }
            });
        }
    }
}

It looks like AppCompatDelegate.setDefaultNightMode doesn't work in PreferenceFragment and PreferenceActivity at all. Is there any way to update day night mode instantly?

回答1:

First of all, you should call getActivity().recreate() to apply the change to the current activity.

But that was not enough, as I used the AppCompatPreferenceActivity template, which seems to be a bit incomplete. I have checked the AppCompatActivity source code and found the code responsible for handling the day/night switch.

private int mThemeId = 0;

...

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    final AppCompatDelegate delegate = getDelegate();
    delegate.installViewFactory();
    delegate.onCreate(savedInstanceState);
    if (delegate.applyDayNight() && mThemeId != 0) {
        // If DayNight has been applied, we need to re-apply the theme for
        // the changes to take effect. On API 23+, we should bypass
        // setTheme(), which will no-op if the theme ID is identical to the
        // current theme ID.
        if (Build.VERSION.SDK_INT >= 23) {
            onApplyThemeResource(getTheme(), mThemeId, false);
        } else {
            setTheme(mThemeId);
        }
    }
    super.onCreate(savedInstanceState);
}

@Override
public void setTheme(@StyleRes final int resid) {
    super.setTheme(resid);
    // Keep hold of the theme id so that we can re-set it later if needed
    mThemeId = resid;
}

After adding it, calling getActivity().recreate() in the preference callback worked as expected.

来源：https://stackoverflow.com/questions/40799202/how-can-you-update-day-night-mode-instantly-in-preferencefragment

标签

java

android

android-fragments