• iOS應(yīng)用程序一共有五種狀態(tài)：

• Not Running 程序還沒運(yùn)行
• Inactive 程序運(yùn)行在foreground但沒有接收事件
• Active 程序運(yùn)行在foreground接收事件
• Background 程序運(yùn)行在background正在執(zhí)行代碼
• Suspended 程序運(yùn)行在background沒有執(zhí)行代碼

• iOS應(yīng)用程序狀態(tài)變化會(huì)回調(diào)APPDelegate中的方法，但不是每一種狀態(tài)變化都會(huì)有對(duì)應(yīng)的方法(上圖的紅框的兩個(gè)變化就沒有對(duì)應(yīng)的方法)

  • application:didFinishLaunchingWithOptions: Not Running -> Inactive
  • applicationDidBecomeActive: Inactive -> Active
  • applicationWillResignActive: Active -> Inactive
  • applicationDidEnterBackground: Background -> Suspended
  • applicationWillEnterForeground: Background -> Inactive
  • applicationWillTerminate: Suspended -> Not Running

• 常見的應(yīng)用狀態(tài)變化場景

  • 程序第一次啟動(dòng)（或者被殺掉以后啟動(dòng)）：
    Not Running -> Inactive -> Active
  • 點(diǎn)擊Home鍵（沒有在Inof.plist中設(shè)置Application does not run in background）：
    Active -> Inactive -> Background -> Suspended
  • 點(diǎn)擊Home鍵（在Inof.plist中設(shè)置Application does not run in background為YES，應(yīng)用不能運(yùn)行在后臺(tái)，進(jìn)入后臺(tái)后會(huì)立即進(jìn)入Not Running）：
    Active -> Inactive -> Background -> Suspended -> Not Running
  • 掛起重新運(yùn)行
    Suspended -> Background -> Inactive -> Active
  • 內(nèi)存清除（殺掉應(yīng)用或刪除應(yīng)用）
    Suspended -> Not Running
  • 應(yīng)用之間的切換
    Active -> Inactive
    Inactive -> Active
  • 點(diǎn)擊Home鍵（在Inof.plist中設(shè)置Application does not run in background為YES，應(yīng)用不能運(yùn)行在后臺(tái)，進(jìn)入后臺(tái)后會(huì)立即進(jìn)入Not Running）：
    Active -> Inactive -> Background -> Suspended -> Not Running

• 可通過在APPDelegate的回調(diào)方法中打印數(shù)據(jù)，來查看應(yīng)用狀態(tài)變化

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        print("`application:didFinishLaunchingWithOptions:`  Not Running -> Inactive")
        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {

        print("`applicationWillResignActive:`  Active -> Inactive")
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        
        print("`applicationDidEnterBackground:`  Background -> Suspended")
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        
        print("`applicationWillEnterForeground:` Background -> Inactive")
    }

    func applicationDidBecomeActive(_ application: UIApplication) {

        print("`applicationDidBecomeActive:`  Inactive -> Active")
    }

    func applicationWillTerminate(_ application: UIApplication) {

        print("`applicationWillTerminate:`  Suspended -> Not Running")
    }