AppDelegate方法调用次序

当点击icon图标进入应用时首先会调用

1. - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
2. - (void)applicationDidBecomeActive:(UIApplication *)application

当点击home键进入后台

1. - (void)applicationWillResignActive:(UIApplication *)application
2. - (void)applicationDidEnterBackground:(UIApplication *)application

点击图标重新进入应用

1. - (void)applicationWillEnterForeground:(UIApplication *)application
2. - (void)applicationDidBecomeActive:(UIApplication *)application

双击home键

1. - (void)applicationWillResignActive:(UIApplication *)application

再点击home键

1. - (void)applicationDidBecomeActive:(UIApplication *)application

在前台双击home键，退出应用

1. - (void)applicationWillResignActive:(UIApplication *)application
2. - (void)applicationDidEnterBackground:(UIApplication *)application
3. - (void)applicationWillTerminate:(UIApplication *)application

在后台 双击home键，退出应用不会接受消息