iOS 系统消息通知

一、键盘
1、UIKeyboardWillShowNotification-将要弹出键盘
2、UIKeyboardDidShowNotification-显示键盘
3、UIKeyboardWillHideNotification-将要隐藏键盘
4、UIKeyboardDidHideNotification-键盘已经隐藏
5、UIKeyboardWillChangeFrameNotification-键盘将要改变frame
6、UIKeyboardDidChangeFrameNotification-键盘已经改变frame

二、窗体
1、UIWindowDidBecomeVisibleNotification-窗体可见
2、UIWindowDidBecomeHiddenNotification-窗体隐藏
3、UIWindowDidBecomeKeyNotification
4、UIWindowDidResignKeyNotification
三、程序消息
1、UIApplicationDidBecomeActiveNotification-程序从后台激活
2、UIApplicationDidChangeStatusBarFrameNotification-状态栏frame改变
3、UIApplicationDidChangeStatusBarOrientationNotification-状态栏方向改变
4、UIApplicationDidEnterBackgroundNotification-进入后台
5、UIApplicationDidFinishLaunchingNotification-程序载入完毕
6、UIApplicationDidReceiveMemoryWarningNotification-内存警告
7、UIApplicationProtectedDataDidBecomeAvailable
8、UIApplicationProtectedDataWillBecomeUnavailable
9、UIApplicationSignificantTimeChangeNotification 重要的时间变化（新的一天開始或时区变化）
10、UIApplicationWillChangeStatusBarOrientationNotification-将要改变状态栏方向
11、UIApplicationWillChangeStatusBarFrameNotification-将要改变状态栏frame
12、UIApplicationWillEnterForegroundNotification
13、UIApplicationWillResignActiveNotification
14、UIApplicationWillTerminateNotification

四、电池、方向、传感器
1、UIDeviceBatteryLevelDidChangeNotification //电池电量
2、UIDeviceBatteryStateDidChangeNotification //电池状态
3、UIDeviceOrientationDidChangeNotification //方向
4、UIDeviceProximityStateDidChangeNotification //近距离传感器

五、音视频
1、MPMediaLibraryDidChangeNotification
2、MPMusicPlayerControllerPlaybackStateDidChangeNotification
3、MPMusicPlayerControllerNowPlayingItemDidChangeNotification
4、MPMusicPlayerControllerVolumeDidChangeNotification

六、其它 
1、NSUserDefaultsDidChangeNotification 用户默认设置变化
2   NSCurrentLocaleDidChangeNotification 本地化语言变化