iOS开发中获取短信验证码倒计时按钮的实现

-(void)startTime{
__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（倒计时结束后调用）
[l_timeButton setTitle:@"发送验证码" forState:UIControlStateNormal];
//设置不可点击
l_timeButton.userInteractionEnabled = YES;
l_timeButton.backgroundColor = [UIColor orangeColor];

});
}else{
//            int minutes = timeout / 60;    //这里注释掉了，这个是用来测试多于60秒时计算分钟的。
int seconds = timeout % 60;
NSString *strTime = [NSString stringWithFormat:@"%d", seconds];
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面的按钮显示 根据自己需求设置
NSLog(@"____%@",strTime);
[l_timeButton setTitle:[NSString stringWithFormat:@"%@秒后可重新发送",strTime] forState:UIControlStateNormal];
//设置可点击
l_timeButton.userInteractionEnabled = NO;
l_timeButton.backgroundColor = [UIColor lightGrayColor];
});
timeout--;
}
});

dispatch_resume(_timer);

}