說在前面：

5個狀態(tài)：not runing 非運行；inactive :前臺非活動；active:前臺活動；background:后臺狀態(tài)；suspended:掛起狀態(tài)

在狀態(tài)變化種，APP會回調(diào)AppDelegate中的相關方法，并發(fā)出對應通知。

場景1：應用啟動：

狀態(tài)變化：not runing ->inactive->active，在not runing->inactive過程中，調(diào)用didFinishLaunchingWithOptions,發(fā)出UIApplicationDidFinishLaunchingNotification通知

inactve->active:調(diào)用didBecomeActive，發(fā)出UIApplicationDidBecomeActiveNotification通知

場景2：應用退出（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)出相應通知

inactive->background:willEnterBackground

background->suspended:didEnterBackground 并發(fā)出相應通知

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)出相應通知

inactive->background:willEnterBackground

background->suspended:didEnterBackground 并發(fā)出相應通知

suspended->not runing:willTerminate,并發(fā)出響應通知

場景3：掛起被用戶喚醒

狀態(tài)變化：suspended->background->inactive->active

場景4：應用終止

backbround->suspended->not runing