Swift

var timer : DispatchSourceTimer?func startTimer() {        var timeCount = 10    // 在global线程里创立一个工夫源    if timer == nil {        timer = DispatchSource.makeTimerSource(queue: DispatchQueue.global())    }    // 设定这个工夫源是每秒循环一次，立刻开始    timer?.schedule(deadline: .now(), repeating: .seconds(1))    // 设定工夫源的触发事件    timer?.setEventHandler(handler: {        //此时处于 global 线程中        print("定时器:",timeCount)        // 每秒计时一次        timeCount = timeCount - 1        // 工夫到了勾销工夫源        if timeCount <= 0 {            self.stopTimer()             DispatchQueue.main.async {                //UI操作放在主线程                            }             }    })    // 启动工夫源    timer?.resume()}//进行定时器func stopTimer() {    print("定时器完结")    timer?.cancel()    timer = nil}

Objective-C

@interface ViewController (){    dispatch_source_t _timer;}@end-(void)startTimer{    __block NSInteger timeCount = 10;    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_global_queue(0, 0));    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 0 * NSEC_PER_SEC);    dispatch_source_set_event_handler(timer, ^{        NSLog(@"定时器:%li",(long)timeCount);        timeCount --;        if (timeCount <= 0) {            [self stopTimer];            dispatch_async(dispatch_get_main_queue(), ^{                            });        }            });    dispatch_resume(timer);    _timer = timer;    }-(void)stopTimer{    dispatch_source_cancel(_timer);    _timer = nil;}

有两点须要留神：

  • 照此办法进行定时器，能够复用，应用suspend进行定时器无奈复用
  • timer 要设置为全局对象。否则代码执行完后 timer 就被开释了；且不便在其余中央操作，如暂停、勾销、置空。