SpriteKit：解开时意外找到零，无法实现多个菜单场景

Question

我试图用2个按钮作为初始场景来呈现菜单：play,credits。当单击play时，我想用4个按钮呈现另一个菜单场景：tutorial，easy，hard,back。
该策略只是将按钮创建为SKSpriteNode对象并处理touchesBegan函数中的点击。

在我的menuScene.sks文件中，我正确放置并命名了我的节点。在这里，你可以检查menuScene.swift文件链接到了这一幕：

import SpriteKit 

class menuScene: SKScene { 

var playButton:SKSpriteNode! 
var creditsButton:SKSpriteNode! 

override func didMove(to view: SKView) { 
    playButton = self.childNode(withName: "playButton") as! SKSpriteNode 
    creditsButton = self.childNode(withName: "creditsButton") as! SKSpriteNode 
} 

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
    // transition is defined in Helper.swift 
    let touch = touches.first 

    if let location = touch?.location(in: self){ 

     let nodesArray = self.nodes(at: location) 

     if nodesArray.first?.name == "playButton" { 
      let nextScene = difScene(size: self.size) 
      self.view?.presentScene(nextScene, transition: transition) 
     } else if nodesArray.first?.name == "creditsButton" { 
      let nextScene = creditsScene(size: self.size) 
      self.view?.presentScene(nextScene, transition: transition) 
     } 
    } 
    } 
} 

当我运行，menuScene呈现没有问题。但是，当我触摸play按钮时，出现错误，它来自下一个场景：difScene。 在这里你可以找到difScene.swift：

import SpriteKit 

class difScene: SKScene { 

var tutButton:SKSpriteNode! 
var easyButton:SKSpriteNode! 
var hardButton:SKSpriteNode! 
var backButton:SKSpriteNode! 

override func didMove(to view: SKView) { 
    tutButton = self.childNode(withName: "tutButton") as! SKSpriteNode // error 
    easyButton = self.childNode(withName: "easyButton") as! SKSpriteNode 
    hardButton = self.childNode(withName: "hardButton") as! SKSpriteNode 
    backButton = self.childNode(withName: "backButton") as! SKSpriteNode 
} 

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
    let transition = SKTransition.push(with: .down, duration: 0.2) 
    let touch = touches.first 

    if let location = touch?.location(in: self){ 

     let nodesArray = self.nodes(at: location) 
     if nodesArray.first?.name == "tutButton" { 

      let nextScene = GameScene(size: self.size) 
      self.view?.presentScene(nextScene, transition: transition) 
     } 

     if nodesArray.first?.name == "easyButton" { 
      let nextScene = difScene(size: self.size) 
      self.view?.presentScene(nextScene, transition: transition) 
     } 

     if nodesArray.first?.name == "hardButton" { 
      let nextScene = difScene(size: self.size) 
      self.view?.presentScene(nextScene, transition: transition) 
     } 

     if nodesArray.first?.name == "backButton" { 
      let nextScene = menuScene(size: self.size) 
      self.view?.presentScene(nextScene, transition: transition) 
     } 
    } 
    } 
} 

在情况下，它可能是有用的，这是我GameViewController.swift：

import UIKit 
import SpriteKit 
import GameplayKit 

class GameViewController: UIViewController { 

override func viewDidLoad() { 
    super.viewDidLoad() 

    if let scene = GKScene(fileNamed: "menuScene") { 

     // Get the SKScene from the loaded GKScene 
     if let sceneNode = scene.rootNode as! menuScene? { 

      // Set the scale mode to scale to fit the window 
      sceneNode.scaleMode = .aspectFill 

      // Present the scene 
      if let view = self.view as! SKView? { 
       view.presentScene(sceneNode) 

       view.ignoresSiblingOrder = true 

       view.showsFPS = false 
       view.showsNodeCount = false 
      } 
     } 
    } 
} 

override var shouldAutorotate: Bool { 
    return true 
} 

override var supportedInterfaceOrientations: UIInterfaceOrientationMask { 
    if UIDevice.current.userInterfaceIdiom == .phone { 
     return .allButUpsideDown 
    } else { 
     return .all 
    } 
} 

override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
    // Release any cached data, images, etc that aren't in use. 
} 

override var prefersStatusBarHidden: Bool { 
    return true 
    } 
} 

我得到的错误是：

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

我知道这是不是一个唯一的错误。我有Google，看过教程，并尝试从其他StackOverflow线程获得解决方案，但未能克服此问题。

Answer 1

的错误是在这条线

tutButton = self.childNode(withName: "tutButton") as! SKSpriteNode // error 

，因为有一个名为“tutButton”无子节点，所以迫使它转换成一SKSpriteNode导致错误。

当按下播放按钮，可以调用此代码：

let nextScene = difScene(size: self.size) 
self.view?.presentScene(nextScene, transition: transition) 

这初始化一个新difScene，并提出它，进而调用代码上方时崩溃行。

对于difScene，您是否有对应的sks文件？在didMove中添加您引用的四个按钮？

如果是这样，你需要像你这样为你的菜单中的场景与sks文件初始化difScene：

let scene = GKScene(fileNamed: "difScene") 

如果没有，您需要创建这四个按钮节点并将它们添加作为孩子以编程方式进入你的场景。

---

旁注：在斯威夫特，惯例是名称以大写字母类型。您的menuScene应该是MenuScene，而您的difScene应该是DifScene。这会让其他人更容易阅读和理解你的代码。