1 前言
使用Dispatch_after ，能够在你想指定一定数量的延迟之后,使用 GCD 来执行代码，
IOS开发之GCD执行延迟操作
。今天我们就来学习一下。2 代码实例
Demo1：
ZYAppDelegate.m
[plain]
- (void) printString:(NSString *)paramString{
NSLog(@"%@", paramString);
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
/*
推迟三秒执行printString方法
withObject:传的参数
*/
[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;
}
- (void) printString:(NSString *)paramString{
NSLog(@"%@", paramString);
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
/*
推迟三秒执行printString方法
withObject:传的参数
*/
[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;
}
运行3秒后控制台结果：
2013-05-10 17:04:52.710 GCDAfterTest[2385:c07] Grand Central Dispatch
Demo2：
ZYAppDelegate.m
[plain]
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//设置时间为2
double delayInSeconds = 2.0;
//创建一个调度时间,相对于默认时钟或修改现有的调度时间，
电脑资料
《IOS开发之GCD执行延迟操作》(https://www.unjs.com)。dispatch_time_t delayInNanoSeconds =dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
//推迟两纳秒执行
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;
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//设置时间为2
double delayInSeconds = 2.0;
//创建一个调度时间,相对于默认时钟或修改现有的调度时间。
dispatch_time_t delayInNanoSeconds =dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
//推迟两纳秒执行
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;
}
运行2秒后控制台结果