__block int timeout = 59; //倒计时时间 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue); dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行 dispatch_source_set_event_handler(_timer, ^{ if(timeout<=0){ //倒计时结束,关闭 dispatch_source_cancel(_timer); dispatch_async(dispatch_get_main_queue(), ^{ //设置界面的按钮显示 根据自己需求设置 [fetchVerifyCodeButton_ setEnabled:YES]; [fetchVerifyCodeButton_ setTitle:@"获取验证码" forState:UIControlStateNormal]; }); }else{ int seconds = timeout % 60; NSString *strTime = [NSString stringWithFormat:@"%2d秒重新获取", seconds]; dispatch_async(dispatch_get_main_queue(), ^{ //设置界面的按钮显示 根据自己需求设置 [fetchVerifyCodeButton_ setTitle:strTime forState:UIControlStateDisabled]; }); timeout--; } }); dispatch_resume(_timer);
普通写法
secondsCountDown = 60;//60秒倒计时 countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeFireMethod) userInfo:nil repeats:YES]; -(void)timeFireMethod{ secondsCountDown--; if(secondsCountDown==0){ [countDownTimer invalidate]; } }