问题现象:想在页面初始化的时候,使用self.presentViewController方法弹出个告警提示框UIAlertController。但行后报了个如下告警,同时告警框也出不来。
解决办法:原来的调用代码是写在viewDidLoad方法中,这个表示视图加载完毕。我们应该把方法调用放到viewDidApper中,这个是UIViewController对象的视图已经加入到窗口时调用。
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2015 - 03 - 10 09 : 55 : 34.197 Test[ 1140 : 29622 ] Warning: Attempt to present <UIAlertController: 0x7c95ca20 > on <Test.ViewController: 0x7a6afc60 > whose view is not in the window hierarchy! |
解决办法:原来的调用代码是写在viewDidLoad方法中,这个表示视图加载完毕。我们应该把方法调用放到viewDidApper中,这个是UIViewController对象的视图已经加入到窗口时调用。
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import UIKit class ViewController : UIViewController , UIActionSheetDelegate { override func viewDidLoad() { super .viewDidLoad() } override func viewDidAppear(animated: Bool ){ super .viewDidAppear(animated) var alertController = UIAlertController (title: "系统提示" , message: "您确定要离开hangge.com吗?" , preferredStyle: UIAlertControllerStyle . Alert ) var cancelAction = UIAlertAction (title: "取消" , style: UIAlertActionStyle . Cancel , handler: nil ) var okAction = UIAlertAction (title: "好的" , style: UIAlertActionStyle . Default , handler: nil ) alertController.addAction(cancelAction) alertController.addAction(okAction) self .presentViewController(alertController, animated: true , completion: nil ) } override func didReceiveMemoryWarning() { super .didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } } |