iOS开发 ☞ UIApplication 生命周期

最新推荐文章于 2022-01-11 16:44:34 发布

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本文详细介绍了iOS应用程序的各种生命周期状态，包括启动、进入前台、进入后台及终止等阶段，并阐述了各个阶段对应的方法调用及其作用。

test enviroment
A Simulator , A lots of codes like this 

- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    NSLog(@"%@",NSStringFromSelector(_cmd));
    return YES;
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    NSLog(@"%@",NSStringFromSelector(_cmd));
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
    NSLog(@"%@",NSStringFromSelector(_cmd));
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
    NSLog(@"%@",NSStringFromSelector(_cmd));
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
    NSLog(@"%@",NSStringFromSelector(_cmd));
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    NSLog(@"%@",NSStringFromSelector(_cmd));
}

- (void)applicationWillTerminate:(UIApplication *)application {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    NSLog(@"%@",NSStringFromSelector(_cmd));

    NSUserDefaults *d = [NSUserDefaults standardUserDefaults];
    [d setObject:@"1" forKey:@"3"];
    [d synchronize];
}

启动：

application:willFinishLaunchingWithOptions:
application:didFinishLaunchingWithOptions:
applicationDidBecomeActive:

点击Home键：

applicationWillResignActive:
applicationDidEnterBackground:

从后台恢复：

applicationWillEnterForeground:
applicationDidBecomeActive:

应用在前台，手动杀死程序

applicationWillResignActive:
applicationDidEnterBackground:
applicationWillTerminate:

应用在后台，手动杀死

Do Nothing，the plist file not exits

我们经常滑动屏幕，查看通知，like this：
这里写图片描述

applicationWillResignActive:

如果你点击了某个通知，跳转到了别的应用，当然要执行

applicationDidEnterBackground:

总结一下:
在一个应用程序的整个生命周期，只会调用一次的方法有

application:willFinishLaunchingWithOptions:
application:didFinishLaunchingWithOptions:
applicationWillTerminate:

其余的则可能被调用多次，要依据情况而定。