iOS开发——生命周期

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本文通过实验详细解析了iOS应用程序的生命周期，包括程序启动、暂停、进入后台、再次激活等关键阶段，并提供了具体的代码示例。

为了处理好应用程序的挂起、暂停等情况下的数据保存，或对应添加所需处理，我们必须了解ios生命周期。

但是不要去背去记，做个实验就好。

    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions  
    {  
        // Override point for customization after application launch.  
        NSLog(@"程序开始");  
        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(@"程序暂停");  
    }  
      
    - (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(@"程序进入后台");  
    }  
      
    - (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(@"程序进入前台");  
    }  
      
    - (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(@"程序再次激活");  
    }  
      
    - (void)applicationWillTerminate:(UIApplication *)application  
    {  
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.  
        NSLog(@"程序意外终止");  
    }

实验结果：

1.首次启动应用程序：

2012-06-26 11:06:39.313 WQTest[485:17903] 程序开始

2012-06-26 11:06:39.320 WQTest[485:17903] 程序再次激活

2.摁HOME键退出：

2012-06-26 11:08:08.687 WQTest[485:17903] 程序暂停

2012-06-26 11:08:08.690 WQTest[485:17903] 程序进入后台

3.再次进入程序：

2012-06-26 11:09:11.047 WQTest[485:17903] 程序进入前台

2012-06-26 11:09:11.049 WQTest[485:17903] 程序再次激活