NSNotificationCenter 系统通知

1. UIDevice:

• UIDeviceOrientationDidChangeNotification // 设备旋转
• UIDeviceBatteryStateDidChangeNotification // 电池状态改变
• UIDeviceBatteryLevelDidChangeNotification // 电池电量改变
• UIDeviceProximityStateDidChangeNotification // 近距离传感器(比如设备贴近了使用者的脸部)

2. keyborard:

• UIKeyboardWillShowNotification  //将要弹出键盘
• UIKeyboardDidShowNotification  //显示键盘
• UIKeyboardWillHideNotification  //将要隐藏键盘
• UIKeyboardDidHideNotification //键盘已经隐藏
• UIKeyboardWillChangeFrameNotification  //键盘将要改变frame
• UIKeyboardDidChangeFrameNotification//键盘已经改变frame

• UIKeyboardFrameBeginUserInfoKey //键盘刚开始的frame

• UIKeyboardFrameEndUserInfoKey //键盘最终的frame(动画执行完毕后)

• UIKeyboardAnimationDurationUserInfoKey //键盘动画的时间

• UIKeyboardAnimationCurveUserInfoKey //键盘动画的执行节奏(快慢)

3. window：

• UIWindowDidBecomeVisibleNotification//窗口可见

• UIWindowDidBecomeHiddenNotification//窗口隐藏
• UIWindowDidBecomeKeyNotification
• UIWindowDidResignKeyNotification

4. Application:

• UIApplicationDidBecomeActiveNotification//程序从后台激活

• UIApplicationDidChangeStatusBarFrameNotification//状态栏frame改变
• UIApplicationDidChangeStatusBarOrientationNotification//状态栏方向改变
• UIApplicationDidEnterBackgroundNotification//进入后台
• UIApplicationDidFinishLaunchingNotification//程序加载完成
• UIApplicationDidReceiveMemoryWarningNotification//内存警告
• UIApplicationProtectedDataDidBecomeAvailable
• UIApplicationProtectedDataWillBecomeUnavailable
• UIApplicationSignificantTimeChangeNotification//重要的时间变化（新的一天开始或时区变化）
• UIApplicationWillChangeStatusBarOrientationNotification//将要改变状态栏方向
• UIApplicationWillChangeStatusBarFrameNotification//将要改变状态栏frame
• UIApplicationWillEnterForegroundNotification
• UIApplicationWillResignActiveNotification
• UIApplicationWillTerminateNotification

5. Media:

• MPMediaLibraryDidChangeNotification

• MPMusicPlayerControllerPlaybackStateDidChangeNotification
• MPMusicPlayerControllerNowPlayingItemDidChangeNotification
• MPMusicPlayerControllerVolumeDidChangeNotification

6. others:

• NSUserDefaultsDidChangeNotification//用户默认设置变化
• NSCurrentLocaleDidChangeNotification//本地化语言变化