单击UITableview行后，UIActivityIndi​​catorView无法显示？

Question

点击后指示器doest显示，首先加载下一页然后显示几毫秒。我想让它从行点击一直到下一个屏幕完全加载。

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{

UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activityIndicator.frame = CGRectMake(0,0,50,50);
activityIndicator.tintColor = [UIColor blackColor];
activityIndicator.center = self.view.center;
[self.view addSubview:activityIndicator];
[activityIndicator startAnimating];

UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
UIViewController *vc = [sb instantiateViewControllerWithIdentifier:@"6"];
vc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentViewController:vc animated:YES completion:NULL];
}

Answer 1

尝试更改代码，以便将UIActivityIndicatorView代码放在主线程上。

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    dispatch_async(dispatch_get_main_queue(), ^{
        UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
        activityIndicator.frame = CGRectMake(0,0,50,50);
        activityIndicator.tintColor = [UIColor blackColor];
        activityIndicator.center = self.view.center;
        [self.view addSubview:activityIndicator];
        [activityIndicator startAnimating];
    });


    UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    UIViewController *vc = [sb instantiateViewControllerWithIdentifier:@"6"];
    vc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self presentViewController:vc animated:YES completion:NULL];
}

Answer 2

你可以试试这个，但你仍然没有在第二个视图控制器中看到任何活动指示器，因为你在第二个视图控制器中没有。

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{

    dispatch_queue_t myQueue = dispatch_queue_create("My Queue",NULL);

    UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    activityIndicator.frame = CGRectMake(0,0,50,50);
    activityIndicator.tintColor = [UIColor blueColor];
    activityIndicator.center = self.view.center;

    dispatch_async(myQueue, ^{
        [self.view addSubview:activityIndicator];
        [activityIndicator startAnimating];
    });

    dispatch_async(dispatch_get_main_queue(), ^{
        UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
        UIViewController *vc = [sb instantiateViewControllerWithIdentifier:@"6"];
        vc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
        [self presentViewController:vc animated:YES completion:^{
            [activityIndicator stopAnimating];
        }];
    });

}

Answer 3

为什么不在下一页显示UIActivityIndicator，直到它加载？

在下一个屏幕上的viewWillappear或viewDidLoad中启动它，在完成加载后结束

Answer 4

您启动UIActivityIndicator，然后转到下一个View Controller。由于快速转换，您只能看一段时间的指标。您可以在其他View Controller上添加活动指示器，并根据需要显示它。