How can I fix "Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value" in Swift

Question

我正在尝试将音乐添加到我创建的游戏中。但我收到错误：

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

我在 Stack Overflow () 上发现了另一个 post，但我不明白这如何适用于我的代码。

这是我的代码：

import UIKit
import SpriteKit
import GameplayKit
import AVFoundation

class GameViewController: UIViewController {
    var player:AVAudioPlayer = AVAudioPlayer()

    override func viewDidLoad() {
        super.viewDidLoad()

        do {
            let audioPath = Bundle.main.path(forResource: "HomeSoundtrack", ofType: "m4a")
            try player = AVAudioPlayer(contentsOf: NSURL(fileURLWithPath: audioPath!) as URL)
        }
        catch {
        }

        let session = AVAudioSession.sharedInstance()

        do {
            try session.setCategory(AVAudioSessionCategoryPlayback)
        }
        catch {
        }

        player.play()

        if let view = self.view as! SKView? {
            // Load the SKScene from 'GameScene.sks'
            if let scene = SKScene(fileNamed: "GameScene") {
                // Set the scale mode to scale to fit the window
                scene.scaleMode = .aspectFill

                // Present the scene
                view.presentScene(scene)
            }

            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
        }
    }
}

Answer 1

在您的代码中，您强制使用 !如果您强制解包的内容恰好为零，则可能会导致此错误。在

try player = AVAudioPlayer(contentsOf: NSURL(fileURLWithPath: audioPath!) as URL)

如果 audioPath 为 nil，这可能会导致错误，最好这样做

//If this line errors, there is a problem with finding HomeSoundtrack.m4a in the bundle
let audioPathURL: URL =  Bundle.main.url(forResource: "HomeSoundtrack", withExtension: "m4a")!
do {
    player = try AVAudioPlayer(contentsOf:  audioPathURL)
} catch {
    print("Couldn't load HomeSoundtrack file with error: \(error)")
}

或在

if let view = self.view as! SKView?

这个 if let 应该看起来像

if let view: SKView = self.view as? SKView {
    //Game stuff
}

Answer 2

可选值是可能包含的值nil如果你想得到它的值你必须包装它

但使用安全包装而不是强制包装!

检查这一行

let audioPath = Bundle.main.path(forResource: "HomeSoundtrack", ofType: "m4a")

audioPath 是一个 Optional 所以它可能包含 nil 值假设你写 HomeSoundtrack 错误或找不到文件那么 audioPath 将为 nil

然后你强制包装 ! 它。在这一行中，如果 audioPath 是 nil 那么它将崩溃

try player = AVAudioPlayer(contentsOf: NSURL(fileURLWithPath: audioPath!) as URL)

可以安全完成

  let audioPathURL =  Bundle.main.url(forResource: "HomeSoundtrack", withExtension: "m4a")
        {
            do {
                player = try AVAudioPlayer(contentsOf:  audioPathURL)
            }  catch {
                print("Couldn't load HomeSoundtrack file")

            }
        }

How can I fix "Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value" in Swift

How can I fix "Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value" in Swift

swift

avaudioplayer

optional

avaudiosession