Night Mode Helper - Helps use utilise the night and notnight resource qualifiers without being in car or dock mode.

NightModeHelper.java

import java.lang.ref.WeakReference;

import android.app.Activity;
import android.content.SharedPreferences;
import android.content.res.Configuration;
import android.preference.PreferenceManager;


/**
 * Night Mode Helper
 * 
 * <p>Helps use utilise the night and notnight resource qualifiers without 
 * being in car or dock mode.
 * 
 * <p>Implementation is simple. Add the follow line at the top of your 
 * activity's onCreate just after the super.onCreate(); The idea here 
 * is to do it before we create any views. So the new views will use 
 * the correct Configuration.
 * 
 * <pre>
 * mNightModeHelper = new NightModeHelper(this, R.style.AppTheme);
 * </pre>
 * 
 * You can now use your instance of NightModeHelper to control which mode 
 * you are in. You can choose to persist the current setting and hand
 * it back to this class as the defaultUiMode, otherwise this is done 
 * for you automatically.
 * 
 * <p>I'd suggest you setup your Theme as follows:
 * 
 * <ul>
 * <li>
 * <b>res\values\styles.xml</b>
 * <pre>&lt;style name=&quot;AppTheme&quot; parent=&quot;AppBaseTheme&quot;&gt;&lt;/style&gt;</pre>
 * </li>
 * <li>
 * <b>res\values-night\styles.xml</b>
 * <pre>&lt;style name=&quot;AppBaseTheme&quot; parent=&quot;@android:style/Theme.Holo&quot;&gt;&lt;/style&gt;</pre>
 * </li>
 * <li>
 * <b>res\values-notnight\styles.xml</b>
 * <pre>&lt;style name=&quot;AppBaseTheme&quot; parent=&quot;@android:style/Theme.Holo.Light&quot;&gt;&lt;/style&gt;</pre>
 * </li>
 * </ul>
 * 
 * 
 * @author Simon Lightfoot <simon@demondevelopers.com>
 * 
 */
public class NightModeHelper
{
	private static final String PREF_KEY = "nightModeState";
	
	private static int sUiNightMode = Configuration.UI_MODE_NIGHT_UNDEFINED;
	
	private WeakReference<Activity> mActivity;
	private SharedPreferences mPrefs;
	
	
	/**
	 * Default behaviour is to automatically save the setting and restore it.
	 */
	public NightModeHelper(Activity activity, int theme)
	{
		int currentMode = (activity.getResources().getConfiguration()
			.uiMode & Configuration.UI_MODE_NIGHT_MASK);
		mPrefs = PreferenceManager.getDefaultSharedPreferences(activity);
		init(activity, theme, mPrefs.getInt(PREF_KEY, currentMode));
	}
	
	/**
	 * If you don't want the autoSave feature and instead want to provide
	 * your own persisted storage for the mode, use the defaultUiMode for it.
	 */
	public NightModeHelper(Activity activity, int theme, int defaultUiMode)
	{
		init(activity, theme, defaultUiMode);
	}
	
	private void init(Activity activity, int theme, int defaultUiMode)
	{
		mActivity = new WeakReference<Activity>(activity);
		if(sUiNightMode == Configuration.UI_MODE_NIGHT_UNDEFINED){
			sUiNightMode = defaultUiMode;
		}
		updateConfig(sUiNightMode);
		
		// This may seem pointless but it forces the Theme to be reloaded
		// with new styles that would change due to new Configuration.
		activity.setTheme(theme);
	}
	
	private void updateConfig(int uiNightMode)
	{
		Activity activity = mActivity.get();
		if(activity == null){
			throw new IllegalStateException("Activity went away?");
		}
		Configuration newConfig = new Configuration(activity.getResources().getConfiguration());
		newConfig.uiMode &= ~Configuration.UI_MODE_NIGHT_MASK;
		newConfig.uiMode |= uiNightMode;
		activity.getResources().updateConfiguration(newConfig, null);
		sUiNightMode = uiNightMode;
		if(mPrefs != null){
			mPrefs.edit()
				.putInt(PREF_KEY, sUiNightMode)
				.apply();
		}
	}
	
	public static int getUiNightMode()
	{
		return sUiNightMode;
	}
	
	public void toggle()
	{
		if(sUiNightMode == Configuration.UI_MODE_NIGHT_YES){
			notNight();
		}
		else{
			night();
		}
	}
	
	public void notNight()
	{
		updateConfig(Configuration.UI_MODE_NIGHT_NO);
		mActivity.get().recreate();
	}
	
	public void night()
	{
		updateConfig(Configuration.UI_MODE_NIGHT_YES);
		mActivity.get().recreate();
	}
}