NSTimer的使用

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一、NSTimer创建方式

1.通过[NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(showAction) userInfo:nil repeats:YES];来创建

打印出来的日志如下

2016-09-03 08:16:32.512 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:35.512 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:38.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:41.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:44.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:47.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:50.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:53.514excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:56.514 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:16:59.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:02.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:05.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:08.514 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:11.514 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:14.514 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:17.513 excersize[535:10412] ++++++++++++++++++++2016-09-03 08:17:20.514 excersize[535:10412] ++++++++++++++++++++

从打印的日志中可以看出该方法是不能实现精确定时的。 ];

2.通过//1.创建NSTimer

    NSTimer * timer = [NSTimer timerWithTimeInterval:5.0 target:self selector:@selector(showAction) userInfo:nil repeats:YES];    //2.把定时器添加到当前的RunLoop中,并选择NSRunLoopCommonModes 运行模式    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

来创建。【注】在该种创建方式下必须将timer添加到相应的RunLoop模式下，否则timer不起作用。

二、精确定时GCD定时器

@interface ViewController ()/****定时器(这里不用带*,因为dispatch_source_t就是个类,内部已经包含了*)*****/@property(nonatomic,strong) dispatch_source_t timer;@end

-(void)gcdTimer{        //0.创建队列    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);    //1.创建一个GCD定时器        dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);    self.timer = timer;    //2.设置定时器开始时间、间隔时间、精准度    /**  第一个参数:要给哪个定时器设置     第二个参数:开始时间     第三个参数:间隔时间     第四个参数:精准度(误差) 一般为0     GCD的单位是纳秒     *     */    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 4 * NSEC_PER_SEC, 0 * NSEC_PER_SEC);    //3.设置定时器要调用的方法    dispatch_source_set_event_handler(timer, ^{        NSLog(@"-------------------------");            });    //4.恢复启动定时器    dispatch_resume(timer);}

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