公司项目新增开屏广告的业务，涉及到关闭倒秒的功能。使用的nstimer去处理这里逻辑
NSTimer的回调方法会被后置的UI更新阻塞，出现卡顿，跳秒的现象
子线程启动NSTImer，回调方法中回归主线程更新UI
__weak __typeof(self) weakSelf = self; dispatch_async(dispatch_get_global_queue(0, 0), ^{ __strong __typeof(weakSelf) strongSelf = weakSelf; if (strongSelf) { strongSelf.countTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:strongSelf selector:@selector(countDown) userInfo:nil repeats:YES]; NSRunLoop *runloop = [NSRunLoop currentRunLoop]; [runloop addTimer:strongSelf.countTimer forMode:NSDefaultRunLoopMode]; [runloop run]; } });
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ [self.jumpBTN setTitle:[NSString stringWithFormat:@"跳过 %lds",(long)self.count] forState:UIControlStateNormal]; });
原文：https://www.cnblogs.com/widgetbox/p/12605871.html