Swift Mac OS-如何在单击按钮时使用Avplayer播放另一个视频/更改视频的URL

Question

我是Swift的新手，我正在尝试制作一个Mac OS应用程序，该应用程序使用Avplayer从应用程序的资源中循环视频后，将其作为窗口的背景。当用户选择菜单项/单击按钮时，背景视频将立即更改为来自应用程序资源的其他视频，并开始将视频循环为窗口的背景。

在本教程之后，该应用程序启动后，我就可以播放第一个视频：（ https：//youtu.be/qgeqcc587w70），我还成功地使视频循环本身无缝地使视频循环本身无缝：（ looping avplayer seameamly seameamlyly looping avplayer）。

我现在面临的问题是选择菜单项/单击一个按钮后，将视频更改为另一个视频。我要使用的方法是更改URL并使用新的URL创建新的Avplayer，并将其影响到Playerview.player.player之后：（单击按钮时，Swift如何在Avplayer中更新视频网址？）但是，每次选择菜单项时，应用程序崩溃都会带有错误" thread 1 exc_bad_instruction（code = exc_i386_invop subcode = 0x0）"。这显然是由于游戏宣言为零而引起的。我并不真正理解这样的原因，因为PlayerView是我使用XIB文件创建的Avplayerview对象，并通过控制拖动链接到Swift文件，我似乎找不到另一种适当的方法来完成我想要的事情去做。如果您知道这样做的原因和解决方法，请为我提供一些帮助，或者如果您知道上面提到的更好的方法，请告诉我。任何帮助将不胜感激！

我的代码如下，崩溃应用程序的行在底部：

import Cocoa
import AppKit
import AVKit
import AVFoundation
struct videoVariables {
    static var videoName = "Test_Video" //declaring the video name as a global variable
}
    var videoIsPlaying = true
    var theURL = Bundle.main.url(forResource:videoVariables.videoName, withExtension: "mp4") //creating the video url
    var player = AVPlayer.init(url: theURL!)
class BackgroundWindow: NSWindowController {    
    @IBOutlet weak var playerView: AVPlayerView! // AVPlayerView Linked using control-drag from xib file
    @IBOutlet var mainWindow: NSWindow!
    @IBOutlet weak var TempBG: NSImageView!
    override var windowNibName : String! {
        return "BackgroundWindow"
    }

//function used for resizing the temporary background image and the playerView to the window’s size
    func resizeBG() {
        var scrn: NSScreen = NSScreen.main()!
        var rect: NSRect = scrn.frame
        var height = rect.size.height
        var width = rect.size.width
        TempBG.setFrameSize(NSSize(width: Int(width), height: Int(height)))
        TempBG.frame.origin = CGPoint(x: 0, y: 0)
        playerView!.setFrameSize(NSSize(width: Int(width), height: Int(height)))
        playerView!.frame.origin = CGPoint(x: 0, y: 0)
    }
    override func windowDidLoad() {
        super.windowDidLoad()   
        self.window?.titleVisibility = NSWindowTitleVisibility.hidden //hide window’s title
        self.window?.styleMask = NSBorderlessWindowMask //hide window’s border
        self.window?.hasShadow = false //hide window’s shadow
        self.window?.level = Int(CGWindowLevelForKey(CGWindowLevelKey.desktopWindow)) //set window’s layer as desktopWindow layer
        self.window?.center()
        self.window?.makeKeyAndOrderFront(nil)
        NSApp.activate(ignoringOtherApps: true)
        if let screen = NSScreen.main() {
            self.window?.setFrame(screen.visibleFrame, display: true, animate: false) //resizing the window to cover the whole screen
        }
        resizeBG() //resizing the temporary background image and the playerView to the window’s size
        startVideo() //start playing and loop the first video as the window’s background  
    }
//function used for starting the video again once it has been played fully
    func playerItemDidReachEnd(notification: NSNotification) {
        playerView.player?.seek(to: kCMTimeZero)
        playerView.player?.play()
    }
//function used for starting and looping the video    
    func startVideo() {
        //set the seeking time to be 2ms ahead to prevent a black screen every time the video loops
        let playAhead = CMTimeMake(2, 100); 
            //loops the video
            NotificationCenter.default.addObserver(forName: .AVPlayerItemDidPlayToEndTime, object:
                playerView.player?.currentItem, queue: nil, using: { (_) in
                    DispatchQueue.main.async {
                        self.playerView.player?.seek(to: playAhead)
                        self.playerView.player?.play()
                    }
                })
        var playerLayer: AVPlayerLayer?
        playerLayer = AVPlayerLayer(player: player)
        playerView?.player = player
        print(playerView?.player)
        playerLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
        player.play()

    }

//changing the url to the new url and create a new AVPlayer then affect it to the playerView.player once the menu item is being selected
    @IBAction func renderBG(_ sender: NSMenuItem) {
        videoVariables.videoName = "Test_Video_2"
        var theNewURL = Bundle.main.url(forResource:videoVariables.videoName, withExtension: "mp4")
        player = AVPlayer.init(url: theNewURL!)
        //!!this line crashes the app with the error "thread 1 exc_bad_instruction (code=exc_i386_invop subcode=0x0)" every time the menu item is being selected!!
        playerView.player = player       
    }
}

此外，背景视频不应该是互动的（例如，用户不能暂停/快速前向视频），因此可以忽略用户互动引起的任何问题。该应用的目的是在用户桌面上播放视频，从而创建运行命令的完全相同的效果：

"/system/library/frameworks/screensaver.framework/resources/screensaverengine.app/contents/macos/screensaverengine-background in Terminal。

任何帮助将不胜感激！

Answer 1

您不需要从URL创建Avplayer。有AVPlayerItem类来操纵播放器播放队列。

let firstAsset = AVURLAsset(url: firstVideoUrl)
let firstPlayerItem = AVPlayerItem(asset: firstAsset)
let player = AVPlayer(playerItem: firstPlayerItem)
let secondAsset = AVURLAsset(url: secondVideoUrl)    
let secondPlayerItem = AVPlayerItem(asset: secondAsset)
player.replaceCurrentItem(with: secondPlayerItem)

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