【IOS基础知识】NSTimer定时器使用

1、声明

NSTimer *timer;
2、定义

timer = [NSTimerscheduledTimerWithTimeInterval:1.0ftarget:selfselector:@selector(updateValue)userInfo:nilrepeats:YES];
以下是调用函数

-(void)updateValue
{

NSLog(@"Hello Timer ");
}
3、打开定时器

-(void)viewWillAppear:(BOOL)animated
{

//开起定时器

[timer
setFireDate:[NSDatedistantPast]];
}
4、关闭定时器

-(void)viewDidDisappear:(BOOL)animated

{

//关闭定时器

[timer
setFireDate:[NSDatedistantFuture]];
}

以下是另外一种GCD timer方法：

1、声明

dispatch_source_t _timer;
2、定义 使用

__weakid weakSelf =self;
double delayInSecond = 0.25;

_timer =dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,
0, 0,dispatch_get_main_queue());

dispatch_source_set_timer(_timer,dispatch_walltime(NULL,
0), (unsigned)(delayInSecond *NSEC_PER_SEC), 0);

dispatch_source_set_event_handler(_timer, ^{[weakSelfupdateValues];});

//开启

dispatch_resume(_timer);

-(void)updateValues
{
NSLog(@"Hello
Timer ");

}

3、释放

dispatch_source_cancel(_timer);

dispatch_release(_timer);