GCD 和Timer

GCD中 进行页面切换的时候 主线程一直刷新倒计时

__block int timeout = 2400; //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); //没秒执行

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

UIAlertView * alert = [[UIAlertView alloc]initWithTitle:@"提示" message:@"即将送达"delegate:nil cancelButtonTitle:nil otherButtonTitles:@"确定",@"取消", nil];

[alert show];

});

}else{

int minutes = timeout / 60;

NSString * strTime = [NSString stringWithFormat:@"%d",minutes];

dispatch_async(dispatch_get_main_queue(), ^{

//设置界面的按钮显示 根据自己需求设置

UIView * timeView = [[UIView alloc]initWithFrame:CGRectMake(10, 140, 150, 150)];

timeView.layer.cornerRadius = 75;

timeView.layer.borderWidth = 4;

timeView.layer.borderColor = [UIColor colorWithRed:0.816 green:0.820 blue:0.824alpha:1.000].CGColor;

timeView.backgroundColor = [UIColor whiteColor];

[_mainView addSubview:timeView];

UILabel * tLabel = [[UILabel alloc]initWithFrame:CGRectMake(55, 0, 60, 60)];

tLabel.text = @"剩余";

tLabel.textColor = [UIColor blackColor];

tLabel.font = [UIFont systemFontOfSize:20];

[timeView addSubview:tLabel];

UILabel * mLabel = [[UILabel alloc]initWithFrame:CGRectMake(35, 30, 100, 100)];

mLabel.text = strTime;

mLabel.font = [UIFont systemFontOfSize:80];

mLabel.textColor = [UIColor redColor];

[timeView addSubview:mLabel];

UILabel * lLabel = [[UILabel alloc]initWithFrame:CGRectMake(55, 100, 60, 60)];

lLabel.text = @"分钟";

lLabel.textColor = [UIColor redColor];

lLabel.font = [UIFont systemFontOfSize:20];

[timeView addSubview:lLabel];

});

timeout--;

}

});

dispatch_resume(_timer);

#pragrm mark ---NSTimer---

1. int secondsCountDown; //倒计时总时长
2. NSTimer *countDownTimer;
3. UILabel *labelText;

1. //创建UILabel 添加到当前view
2. labelText=[[UILabel alloc]initWithFrame:CGRectMake(10, 120, 120, 36)];
3. [self.view addSubview:labelText];
4. //设置倒计时总时长
5. secondsCountDown = 60;//60秒倒计时
6. //开始倒计时
7. countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeFireMethod) userInfo:nil repeats:YES]; //启动倒计时后会每秒钟调用一次方法 timeFireMethod
8. //设置倒计时显示的时间
9. labelText.text=[NSString stringWithFormat:@"%d",secondsCountDown];

1. -(void)timeFireMethod{
2. //倒计时-1
3. secondsCountDown--;
4. //修改倒计时标签现实内容
5. labelText.text=[NSString stringWithFormat:@"%d",secondsCountDown];
6. //当倒计时到0时，做需要的操作，比如验证码过期不能提交
7. if(secondsCountDown==0){
8. [countDownTimer invalidate];
9. [labelText removeFromSuperview];
10. }
11. }