尝试在视图不在窗口层次结构中的 UIViewController 上呈现 GKGameCenterViewController

Question

当用户按下我的 SecondViewController 上的按钮（带有得分/最高得分的游戏结束屏幕）时，我无法显示 Game Center 排行榜。 UIbutton 是 ShowLeaderboard，您将在下面看到。

我得到的错误是：

Warning: Attempt to present <GKGameCenterViewController: 0x7fb1c88044a0> on <UIViewController: 0x7fb1c2624e90> whose view is not in the window hierarchy!

我尝试过先关闭视图，但无论我做什么，我都不能只显示排行榜视图。下面是我的 SecondViewController 代码：

import UIKit
import GameKit

class SecondViewController: UIViewController, GKGameCenterControllerDelegate {


@IBOutlet var scoreLabel: UILabel!
@IBOutlet var HighScoreLabel: UILabel!
var receivedString: String = ""
var receivedHighScore: String = ""


override func viewDidLoad() {
    super.viewDidLoad()
    scoreLabel.text = receivedString
    HighScoreLabel.text = receivedHighScore

}


@IBAction func ShowLeaderboard(sender: UIButton) {
    dismissViewControllerAnimated(true, completion:nil)
    showLeader()
}


func showLeader() {
    var vc = self.view?.window?.rootViewController
    var gc = GKGameCenterViewController()
    gc.gameCenterDelegate = self
    vc?.presentViewController(gc, animated: true, completion: nil)
}



func gameCenterViewControllerDidFinish(gameCenterViewController: GKGameCenterViewController!)
{
    gameCenterViewController.dismissViewControllerAnimated(true, completion: nil)

}






override func prefersStatusBarHidden() -> Bool {
    return true
}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}


@IBAction func retryButton(sender: AnyObject) {
    self.dismissViewControllerAnimated(true, completion: nil)
}
}

编辑 搞定了！我所要做的就是改变

var vc = self.view?.window?.rootViewController

到

var vc = self

Answer 1

Here is my Code. Hope it helps! 

if (self.levelGameAttemptCount == 3)
                    {
                        self.canRestart = false

                        let mainStoryboard = UIStoryboard(name: "Main", bundle: nil)
                        let vc = mainStoryboard.instantiateViewControllerWithIdentifier("gameOverControllerID") as! GameOverController
                        self.view!.window!.rootViewController!.dismissViewControllerAnimated(false, completion: nil)
                        UIApplication.sharedApplication().keyWindow!.rootViewController!.presentViewController(vc, animated: true, completion: nil)
                    }
                    else
                    {
                        self.canRestart = true
                    }

Answer 2

您可能会看到此警告，因为您在 dismissViewControllerAnimated 完成动画之前显示排行榜。您应该将showLeader() 放在dismissViewControllerAnimated 的完成参数中。