說在前面：
5個(gè)狀態(tài)：not runing 非運(yùn)行；inactive :前臺(tái)非活動(dòng)；active:前臺(tái)活動(dòng)；background:后臺(tái)狀態(tài)；suspended:掛起狀態(tài)
在狀態(tài)變化種，APP會(huì)回調(diào)AppDelegate中的相關(guān)方法，并發(fā)出對(duì)應(yīng)通知。
場(chǎng)景1：應(yīng)用啟動(dòng)：
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(chǎng)景2：應(yīng)用退出（點(diǎn)擊HOME鍵）
狀態(tài)變化1：可在后臺(tái)運(yùn)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(tái)運(yùn)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(chǎng)景3：掛起被用戶喚醒
狀態(tài)變化：suspended->background->inactive->active
場(chǎng)景4：應(yīng)用終止
backbround->suspended->not runing
