IOS開發（63）之GCD執行延遲操作

1 前言

 

使用Dispatch_after ，能夠在你想指定一定數量的延遲之後,使用 GCD 來執行代碼。今天我們就來學習一下。

 

2 代碼執行個體

Demo1：

ZYAppDelegate.m

 

- (void) printString:(NSString *)paramString{    NSLog(@"%@", paramString);}- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    /*     延遲三秒執行printString方法     withObject:傳的參數     */    [self performSelector:@selector(printString:) withObject:@"Grand Central Dispatch" afterDelay:3.0];    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];    // Override point for customization after application launch.    self.viewController = [[[ZYViewController alloc] initWithNibName:@"ZYViewController" bundle:nil] autorelease];    self.window.rootViewController = self.viewController;    [self.window makeKeyAndVisible];    return YES;}

 

運行3秒後控制台結果：

 

2013-05-10 17:04:52.710 GCDAfterTest[2385:c07] Grand Central Dispatch

Demo2：

ZYAppDelegate.m

 

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    //設定時間為2    double delayInSeconds = 2.0;    //建立一個調度時間,相對於預設時鐘或修改現有的調度時間。    dispatch_time_t delayInNanoSeconds =dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);    //延遲兩納秒執行    dispatch_queue_t concurrentQueue =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    dispatch_after(delayInNanoSeconds, concurrentQueue, ^(void){        NSLog(@"Grand Center Dispatch!");    });        self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];    // Override point for customization after application launch.    self.viewController = [[[ZYViewController alloc] initWithNibName:@"ZYViewController" bundle:nil] autorelease];    self.window.rootViewController = self.viewController;    [self.window makeKeyAndVisible];    return YES;}

 

運行2秒後控制台結果

 

2013-05-10 17:06:27.023 GCDAfterTest2[2435:1303] Grand Center Dispatch!

Demo3：

ZYAppDelegate.m

 

void processSomething(void *paramContext){    NSLog(@"Processing...");}- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    //設定時間    double delayInSeconds = 2.0;    dispatch_time_t delayInNanoSeconds =    dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);    dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    //調用C函數processSomething    dispatch_after_f(delayInNanoSeconds, concurrentQueue,                     NULL,                     processSomething);    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];    // Override point for customization after application launch.    self.viewController = [[[ZYViewController alloc] initWithNibName:@"ZYViewController" bundle:nil] autorelease];    self.window.rootViewController = self.viewController;    [self.window makeKeyAndVisible];    return YES;}

 

運行2秒後控制台結果

 

2013-05-10 17:07:27.660 GCDAfterTest3[2476:1303] Processing...

3 結語

以上是所有內容，希望對大家有所協助。

Demo代碼下載：http://download.csdn.net/detail/u010013695/5353603