方法不调用dispatch_async并重复NSTimer
我正在开发一个应用程序，我想使用dispatch_async在单独的队列中调用方法。 我想在一定的时间间隔后反复调用这个方法。 但是这个方法没有被调用。
我不知道什么是错的。 这是我的代码：
dispatch_async( NotificationQueue, ^{ NSLog(@"inside queue"); timer = [NSTimer scheduledTimerWithTimeInterval: 20.0 target: self selector: @selector(gettingNotification) userInfo: nil repeats: YES]; dispatch_async( dispatch_get_main_queue(), ^{ // Add code here to update the UI/send notifications based on the // results of the background processing }); }); -(void)gettingNotification { NSLog(@"calling method "); }
如果要在dispatch_queue_t上调用重复计时器，请使用dispatch_source_create和DISPATCH_SOURCE_TYPE_TIMER ：
dispatch_queue_t queue = dispatch_queue_create("com.firm.app.timer", 0); dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue); dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), 20ull * NSEC_PER_SEC, 1ull * NSEC_PER_SEC); dispatch_source_set_event_handler(timer, ^{ // stuff performed on background queue goes here NSLog(@"done on custom background queue"); // if you need to also do any UI updates, synchronize model updates, // or the like, dispatch that back to the main queue: dispatch_async(dispatch_get_main_queue(), ^{ NSLog(@"done on main queue"); }); }); dispatch_resume(timer);
这会创build一个每20秒运行一次的计时器（第三个参数为dispatch_source_set_timer ），具有一秒的余地（第四个参数为dispatch_source_set_timer ）。
要取消此计时器，请使用dispatch_source_cancel ：
dispatch_source_cancel(timer);
试试这个代码
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ dispatch_async( dispatch_get_main_queue(), ^{ timer = [NSTimer scheduledTimerWithTimeInterval: 1.0 target: self selector: @selector(gettingNotification) userInfo: nil repeats: YES]; // Add code here to update the UI/send notifications based on the // results of the background processing }); }); -(void)gettingNotification { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ //background task here dispatch_async( dispatch_get_main_queue(), ^{ // update UI here ); }); }
int parameter1 = 12; float parameter2 = 144.1; // Delay execution of my block for 10 seconds. dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 10 * NSEC_PER_SEC), dispatch_get_current_queue(), ^{ NSLog(@"parameter1: %d parameter2: %f", parameter1, parameter2); });
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