ios - 尝试在 上呈现 ，它已经在 swift 中呈现

Question

好的，我正在添加一个请稍候弹出窗口，以便在我的 iOS 应用程序中执行比平时花费更长的时间的操作。

我有一个从 ViewController 到 TabController 的连接，当我像这样调用它时:

self.performSegueWithIdentifier("openMainApp", sender: self)

一切正常。

但是当我用以下内容包围它时:

let alert = UIAlertController(title: nil, message: "Please wait...", preferredStyle: .Alert)

alert.view.tintColor = UIColor.blackColor()
let loadingIndicator: UIActivityIndicatorView = UIActivityIndicatorView(frame: CGRectMake(10, 5, 50, 50)) as UIActivityIndicatorView
loadingIndicator.hidesWhenStopped = true
loadingIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.Gray
loadingIndicator.startAnimating();

alert.view.addSubview(loadingIndicator)
presentViewController(alert, animated: true, completion: nil)

    self.performSegueWithIdentifier("openMainApp", sender: self)

dismissViewControllerAnimated(false, completion: nil)

然后我收到警告:

Warning: Attempt to present <app.TabController: 0x7ff6dc00bd40>  
on <app.ViewController: 0x7ff6d9cf6600> which is already presenting 
<UIAlertController: 0x7ff6d9d78530>

如何跳过此警告？

Answer 1

虽然此警告的来源对我来说仍然是个谜，但有一种方法可以跳过该警告。

1. 从 Storyboard 中删除转场

2. 将 Storyboard ID 提供给 View Controller ，例如:

   

3. 替换self.performSegueWithIdentifier(“openMainApp”，发件人:self)与

   let viewController: UIViewController =
     self.storyboard!.instantiateViewControllerWithIdentifier("MainScene")
   self.presentViewController(viewController, animated: true, completion: nil)