延时执行的方法:
- (void)delay3 { // 3秒后回到主线程执行block中的代码 // dispatch_queue_t queue = dispatch_get_main_queue(); // dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), queue, ^{ // NSLog(@"------task------%@", [NSThread currentThread]); // }); // 3秒后自动开启新线程 执行block中的代码 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), queue, ^{ NSLog(@"------task------%@", [NSThread currentThread]); }); } - (void)delay2 { // 一旦定制好延迟任务后,不会卡住当前线程 [self performSelector:@selector(download:) withObject:@"http://555.jpg" afterDelay:3]; } - (void)delay1 { // 延迟执行不要用sleep,坏处:卡住当前线程 [NSThread sleepForTimeInterval:3]; NSLog(@"-----下载图片-----"); }
一次性代码:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"----touchesBegan"); static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ NSLog(@"----once"); }); }