__block int timeout=60;
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){
dispatch_source_cancel(_timer);
dispatch_async(dispatch_get_main_queue(), ^{
[self.validBtn setTitle:@"获取短信验证码" forState:UIControlStateNormal];
//self.validBtn.backgroundColor=RGB(120, 0, 103);
[self.validBtn setBackgroundImage:[UIImage imageNamed:@"获取验证码"] forState:UIControlStateNormal];
self.validBtn.userInteractionEnabled = YES;
});
}else{
int seconds = timeout;
NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];
dispatch_async(dispatch_get_main_queue(), ^{
[self.validBtn setTitle:[NSString stringWithFormat:@"%@秒",strTime] forState:UIControlStateNormal];
//self.validBtn.backgroundColor=RGB(207, 207, 207);
[self.validBtn setBackgroundImage:[UIImage imageNamed:@"获取验证码-不可点击"] forState:UIControlStateNormal];
self.validBtn.userInteractionEnabled = NO;
});
timeout--;
}
});
dispatch_resume(_timer);
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
Terminate the thread when leaving the current page, and then initialize the countdown to 60
The timer needs to run in the Runloop
After you go to the background, if you are not declared as a program that can run in the background, NSTimer should not go away.
If it were me:
1. Stop the Timer before entering the background, record the time in the applicationDidEnterBackground of the appdelegate, compare the time when entering the foreground, calculate the difference, refresh the verification code value display, and then start the Timer.
2. Stop the Timer before entering the background, or use backgroundTask to decrement the verification code number every few seconds in the background, return to the front desk, and then start the Timer. (This is so boring...)
3. Declare your App as a program that can run in the background.
I would choose the first one. . .
My plan is as follows:
-
I am usingRecord start time.
Update the display on the interface every second, use
Current Time - Start Timeto get the number of seconds displayed on the interface当前时间 - 开始时间得到秒数显示在界面上我使用的是
GCD TimerGCD Timer. There is no need to additionally handle the situation when entering the background and then returning to the foreground. Of course, it is no problem to use other ones. Just handle the things here. 🎜🎜 🎜You can try the following solutions.
GreedTimer can solve the problem you mentioned. When using GRTimer
timeInBackground设置为YESNone of the methods mentioned above work. I found a simple and feasible one.
http://www.jianshu.com/p/8e61...