NSTimer不準，scheduleTimer放在runloop里面，受runloop模式影響會不準
//? ? [NSTimer scheduledTimerWithTimeInterval:<#(NSTimeInterval)#> target:<#(nonnull id)#> selector:<#(nonnull SEL)#> userInfo:<#(nullable id)#> repeats:<#(BOOL)#>];
所以創建GCD定時器
//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#>
//});
//? ? [NSTimer scheduledTimerWithTimeInterval:<#(NSTimeInterval)#> target:<#(nonnull id)#> selector:<#(nonnull SEL)#> userInfo:<#(nullable id)#> repeats:<#(BOOL)#>];
所以創建GCD定時器
//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);
看下面實例：
#import "ViewController.h"@interface ViewController ()
/** 定時器（這里不用帶*，因為dispatch_source_t就是個類，內部包含了） */
@property (nonatomic, strong) dispatch_source_t timer;
@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];//獲得隊列dispatch_queue_t dispatchQueue = dispatch_get_global_queue(0, 0);//創建一個gcd定時器 (dispatch_source_t timer:dispatch_source_t本質還是個OC對象，是個局部變量，需要強引用，不然下面使用無效)self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatchQueue);//OC對象%@可以打印NSLog(@"%@", self.timer);//設置定時器的各種屬性（幾時開始，每隔多長時間執行一次）//GCD時間參數，一般是納秒 NSEC_PER_SEC 納秒單位等于一秒；DISPATCH_TIME_NOW當前時間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]);});//啟動定時器dispatch_resume(self.timer);
}-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {NSLog(@"----touchesBegan點擊取消定時器!");dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{//取消定時器dispatch_cancel(self.timer);self.timer = nil;NSLog(@"%@",self.timer);});
}
@end實例可直接使用，可以封裝成timer類使用，懂了的請點贊哦！！！
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