//倒计时时间
__block int timeout= 2;
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(), ^{
//倒计时结束，开始设置操作
aButton.userInteractionEnabled = YES;
});
}else{
// int minutes = timeout / 60;
// int seconds = timeout % 60;
// NSString *strTime = [NSString stringWithFormat:@"%d分%.2d秒后重新获取验证码",minutes, seconds];
dispatch_async(dispatch_get_main_queue(), ^{
//开始倒计时，设置倒计时显示
aButton.userInteractionEnabled = NO;
});
timeout--;
}
});
dispatch_resume(_timer);
