/**重新發(fā)送短信的計時*/
-(void)fireTimer{
 __block int timeout=180; //倒計時時間
 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); //每秒執(zhí)行

 dispatch_source_set_event_handler(_timer, ^{
  if(timeout<=0){ //倒計時結束，關閉
   dispatch_source_cancel(_timer);
   dispatch_async(dispatch_get_main_queue(), ^{
    //設置界面的按鈕顯示 根據自己需求設置
    [_changeCodeButton setTitle:@"獲取驗證碼" forState:UIControlStateNormal];
    _changeCodeButton.userInteractionEnabled = YES;
   });
  }else{
   int seconds = timeout ;//% 60;
   NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];
   dispatch_async(dispatch_get_main_queue(), ^{
    //設置界面的按鈕顯示 根據自己需求設置
    //NSLog(@"____%@",strTime);
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1];
    _changeCodeButton.titleLabel.font = [UIFont systemFontOfSize:14];
    [_changeCodeButton setTitle:[NSString stringWithFormat:@"(%@s)后重新獲取",strTime] forState:UIControlStateNormal];
    [UIView commitAnimations];
    _changeCodeButton.userInteractionEnabled = NO;
   });
   timeout--;
  }
 });
 dispatch_resume(_timer);
}