NSTimer不准确与GCDTimer详解

超、凢脫俗 2021-09-14 14:34 324阅读 0赞

NSTimer不准，scheduleTimer放在runloop里面，受runloop模式影响会不准  
//    \[NSTimer scheduledTimerWithTimeInterval:<\#(NSTimeInterval)\#> target:<\#(nonnull id)\#> selector:<\#(nonnull SEL)\#> userInfo:<\#(nullable id)\#> repeats:<\#(BOOL)\#>\];  
  
所以创建GCD定时器  
//dispatch\_source\_t timer = dispatch\_source\_create(DISPATCH\_SOURCE\_TYPE\_TIMER, 0, 0, <\#dispatchQueue\#>);  
//dispatch\_source\_set\_timer(timer, DISPATCH\_TIME\_NOW, <\#intervalInSeconds\#> \* NSEC\_PER\_SEC, <\#leewayInSeconds\#> \* NSEC\_PER\_SEC);  
//dispatch\_source\_set\_event\_handler(timer, ^\{  
//    <\#code to be executed when timer fires\#>  
//\});

//dispatch\_resume(timer);

看下面实例：

#import "ViewController.h"
    
    @interface ViewController ()
    /** 定时器（这里不用带*，因为dispatch_source_t就是个类，内部包含了） */
    @property (nonatomic, strong) dispatch_source_t timer;
    @end
    
    @implementation ViewController
    
    - (void)viewDidLoad {
        [super viewDidLoad];
        //获得队列
        dispatch_queue_t dispatchQueue = dispatch_get_global_queue(0, 0);
        //创建一个gcd定时器 (dispatch_source_t timer:dispatch_source_t本质还是个OC对象，是个局部变量，需要强引用，不然下面使用无效)
        self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatchQueue);
        //OC对象%@可以打印
        NSLog(@"%@", self.timer);
        //设置定时器的各种属性（几时开始，每隔多长时间执行一次）
        //GCD时间参数，一般是纳秒 NSEC_PER_SEC 纳秒单位等于一秒；DISPATCH_TIME_NOW当前时间
        dispatch_time_t start = DISPATCH_TIME_NOW;
        uint64_t interval = (uint64_t)(2.0 *NSEC_PER_SEC);
        dispatch_source_set_timer(self.timer, start, interval, 0);
        dispatch_source_set_event_handler(self.timer, ^{
            NSLog(@"--------%@",[NSThread currentThread]);
        });
        //启动定时器
        dispatch_resume(self.timer);
    }
    
    -(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
        NSLog(@"----touchesBegan点击取消定时器!");
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            //取消定时器
                dispatch_cancel(self.timer);
                self.timer = nil;
            NSLog(@"%@",self.timer);
        });
    }
    @end

实例可直接使用，可以封装成timer类使用，懂了的请点赞哦！！！