ios—iPhone开发之生命周期

在初次接触iPhone开发的时候，简直就是一头雾水，这是哪里跟哪里啊?本是做Android开发的我，第一次建立iPhone开发而得到初始代码，心里那纠结比我初次接触Android的情况还要糟糕!不说那么多废话了，第一编文章首先来熟悉一下iPhone程序的生命周期吧，这对整个开发周期也是非常有用的!

iPhone app 与 Android app在生命周期在大体上是相同，但是不同的时Android的程序生命周期都体现在每个页面Activity上，也就是说，在开发Android app的时候，我们只需要管理好每个页面Activity的生命周期，app的生命周期就无需我们太操心了!而iPhone app是严格按照MVC模型开发出来的程序，“委托”这一概念是非常重要的，理所当然，iPhone app的生命周期也是在“委托”上实现的，我们在建立iPhone app的初始状态就可以看到两个文件：AppDelegate.h和AppDelegate.m!这两个文件就是我刚刚所说的“委托”的头文件和实现文件!AppDelegate.m上就可以看到app的生命周期所触发全部方法!iPhone的生命周期分为两种，一是程序的生命周期，二是视图(也就是相当于Android的Activity)的生命周期!

首先，介绍程序的生命周期：(表述能力有待提高，上代码最实际)

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//首次加载，触发的方法，开始加载程序

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

NSLog(@"app didFinishLaunchingWithOptions");

self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

// Override point for customization after application launch.

self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController" bundle:nil] autorelease];

self.window.rootViewController = self.viewController;

[self.window makeKeyAndVisible];

return YES;

}

//当用户点击菜单健，程序放弃激活状态

- (void)applicationWillResignActive:(UIApplication *)application

{

NSLog(@"applicationWillResignActive");

}

//进入后台，线程被挂起

- (void)applicationDidEnterBackground:(UIApplication *)application

{

NSLog(@"applicationDidEnterBackground");

}

//程序未结束，点击程序返回前台，再次获取激活状态，触发applicationDidBecomeActive方法!

- (void)applicationWillEnterForeground:(UIApplication *)application

{

NSLog(@"applicationWillEnterForeground");

}

//完成激活，可以与用户交互

- (void)applicationDidBecomeActive:(UIApplication *)application

{

NSLog(@"applicationDidBecomeActive");

}

//程序结束时触发

- (void)applicationWillTerminate:(UIApplication *)application

{

NSLog(@"applicationWillTerminate");

}

下面让我们看一下视图的生命周期：

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- (void)viewDidLoad

{

[super viewDidLoad];

NSLog(@"viewDidLoad");

}

- (void)viewDidUnload

{

[super viewDidUnload];

secondViewController = nil;

NSLog(@"viewDidUnload");

}

-(void)viewWillAppear:(BOOL)animated

{

[super viewWillAppear:YES];

NSLog(@"viewWillAppear");

}

-(void)viewDidAppear:(BOOL)animated

{

[super viewDidAppear:YES];

NSLog(@"viewDidAppear");

}

-(void)viewDidDisappear:(BOOL)animated

{

[super viewDidDisappear:YES];

NSLog(@"viewDidDisappear");

}

-(void)viewWillDisappear:(BOOL)animated

{

[super viewWillDisappear:YES];

NSLog(@"viewWillDisappear");

}

从方法名，我们都可以看得出，视图生命周期里面大概触发的方法。

现在我们运行一下程序，然后从第一个视图切换到第二个视图，再回到第一个视图。让我们看一下，从程序、视图的出现，消亡所触发的所有方法： #

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2012-05-10 11:29:13.426 iPhoneLifeCycle[877:f803] app didFinishLaunchingWithOptions

2012-05-10 11:29:13.459 iPhoneLifeCycle[877:f803] viewDidLoad

2012-05-10 11:29:13.462 iPhoneLifeCycle[877:f803] viewWillAppear

2012-05-10 11:29:13.465 iPhoneLifeCycle[877:f803] applicationDidBecomeActive

2012-05-10 11:29:13.472 iPhoneLifeCycle[877:f803] viewDidAppear

2012-05-10 11:29:15.054 iPhoneLifeCycle[877:f803] viewWillDisappear

2012-05-10 11:29:15.061 iPhoneLifeCycle[877:f803] viewDidDisappear

2012-05-10 11:29:16.476 iPhoneLifeCycle[877:f803] viewDidLoad

2012-05-10 11:29:16.478 iPhoneLifeCycle[877:f803] viewWillAppear

2012-05-10 11:29:16.483 iPhoneLifeCycle[877:f803] viewDidAppear

2012-05-10 11:29:21.790 iPhoneLifeCycle[877:f803] applicationWillResignActive

2012-05-10 11:29:21.796 iPhoneLifeCycle[877:f803] applicationDidEnterBackground