Question

我有一个奇怪的问题，我需要动画if (chbInsurance.Checked == true) txtCost.Text = ((Convert.ToDouble(txtHours.Text.ToString())) * costPerHour + costOfInsurance).ToString();当我从Activity Indicator选择Cell时。

我的问题是在使用断点调试代码时，CollectionView是动画的，但在运行应用Activity Indicator时没有出现断点。请帮助。

Activity Indicator

Answer 1

看起来dispatch_get_global_queue根本没用过！

一切都在主线程上运行，这对它来说是一个巨大的负担。删除'dispatch_async'块仅在主线程中使用，ui元素会更新。

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
 dispatch_async(dispatch_get_main_queue(), ^{
   //Keep rest of code lines here...
   });
});

如果仍然看不到活动指标，则尝试将繁重的任务移至后台线程并显示活动指示符，如

 loading = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
loading.frame = CGRectMake(round((self.view.frame.size.width - 25) / 2), round((self.view.frame.size.height - 25) / 2), 25, 25);

[self.view addSubview:loading];
[loading startAnimating];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

    //Heavy tasks at background thread
      NSString *videoStringUrl=[NSString stringWithFormat:@"%@",[[arrayPhotos objectAtIndex:indexPath.row]valueForKey:@"source"]];
      VideoURL=[NSURL URLWithString:videoStringUrl];

    dispatch_async(dispatch_get_main_queue(), ^{

     //After completion stop animating activity indicator 
      [loading stopAnimating];

        AVURLAsset *sourceAsset = [AVURLAsset URLAssetWithURL:VideoURL options:nil];
        CMTime duration = sourceAsset.duration;
        float seconds = CMTimeGetSeconds(duration);
        if (seconds<4) {
            [self performSegueWithIdentifier:@"Edit" sender:self];
        }
        else
        {
            [self performSegueWithIdentifier:@"Trimmer" sender:self];
        }

    });});

Answer 2

你正在改变队列，所以经常有一些延迟来解决它。

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC),     dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
     dispatch_async(dispatch_get_main_queue(), ^{
      //Keep rest of code lines here...
   });
});

活动指标不可见

2 个答案: