說在前面：
5個狀態(tài)：not runing 非運行腋舌；inactive :前臺非活動送矩；active:前臺活動澄暮；background:后臺狀態(tài)搅荞；suspended:掛起狀態(tài)
在狀態(tài)變化種，APP會回調(diào)AppDelegate中的相關(guān)方法幽污，并發(fā)出對應(yīng)通知嚷辅。
場景1：應(yīng)用啟動：
狀態(tài)變化：not runing ->inactive->active，在not runing->inactive過程中距误，調(diào)用didFinishLaunchingWithOptions,發(fā)出UIApplicationDidFinishLaunchingNotification通知
inactve->active:調(diào)用didBecomeActive簸搞，發(fā)出UIApplicationDidBecomeActiveNotification通知
場景2：應(yīng)用退出（點擊HOME鍵）
狀態(tài)變化1：可在后臺運行并掛起：active->inactive->background->suspended
active->inactive:回調(diào)WillResignActive并發(fā)出相應(yīng)通知
inactive->background:willEnterBackground
background->suspended:didEnterBackground 并發(fā)出相應(yīng)通知
狀態(tài)變化1：不可在后臺運行并掛起：active->inactive->background->suspended->not runing
active->inactive:回調(diào)WillResignActive并發(fā)出相應(yīng)通知
inactive->background:willEnterBackground
background->suspended:didEnterBackground 并發(fā)出相應(yīng)通知
suspended->not runing:willTerminate,并發(fā)出響應(yīng)通知
場景3：掛起被用戶喚醒
狀態(tài)變化：suspended->background->inactive->active
場景4：應(yīng)用終止
backbround->suspended->not runing
