实际开发中，我们需要用到验证码这个功能，那么问题就来了，怎么实现Button的动态显示倒计时呢？效果图如下：
示意图.png
实现代码如下：
//获取验证码
-(void)getVerifyCode:(UIButton *)sender{
__block int timeout = 60; //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(), ^{
sender.userInteractionEnabled = YES;
sender.backgroundColor = [UIColor whiteColor];
[sender setTitle:@"再次获取验证码" forState:UIControlStateNormal];
});
}
else
{
dispatch_async(dispatch_get_main_queue(), ^{
sender.userInteractionEnabled = NO;
sender.backgroundColor = [UIColor lightGrayColor];
[sender setTitle:[NSString stringWithFormat:@"%ds",timeout] forState:UIControlStateNormal];
});
timeout--;
}
});
dispatch_resume(timer);
}
