Swift 3中退出全屏时AVPlayerViewController报错问题

我之前在做类似的YouTube嵌入播放功能时，也碰到过这个AVPlayerViewController的报错，结合你的代码和问题场景，给你几个针对性的解决方案：

首先还原你的问题场景：

将当应用退出全屏且界面UI向上滑动时，控制台出现如下报错信息：
-[AVPlayerViewController exitFullScreenAnimated:completionHandler:] failed with error View needs to be loaded before you can call -[AVPlayerViewController (0x1028b5000) exitFullScreenAnimated:completionHandler:]!

你的实现方式是通过UIWebView嵌入YouTube iframe播放视频，相关代码如下：

var webView = UIWebView(frame: self.view.frame)
webView.allowsInlineMediaPlayback = true
webView.mediaPlaybackRequiresUserAction = false

embededHTML = "<html><body style='margin:0px;padding:0px;'><script type='text/javascript' src='http://www.youtube.com/iframe_api'></script><script type='text/javascript'>function onYouTubeIframeAPIReady(){ytplayer=new YT.Player('playerId',{events:{onReady:onPlayerReady}})}function onPlayerReady(a){a.target.playVideo();}</script><iframe id='playerId' type='text/html' width='\(self.view.frame.size.width)' height=\(frameHeight) src='http://www.youtube.com/embed/\(youtube_code)?enablejsapi=1&rel=0&playsinline=1&autoplay=1&showinfo=0&modestbranding=0' frameborder='0'></body></html>"

@IBAction func playVideo(_ sender: Any) {
    if let webView = webView {
        self.view.bringSubview(toFront: webView)
        webView.scrollView.isScrollEnabled = false;
        webView.scrollView.bounces = false;
        // Load your webView with the HTML we just set up
        webView.loadHTMLString(embededHTML, baseURL: Bundle.main.bundleURL)
    }
}

1. 替换UIWebView为WKWebView（优先推荐） #

UIWebView已经在iOS 12之后被苹果废弃，它对媒体播放的兼容性和稳定性都远不如WKWebView。换成WKWebView后，很多底层的媒体播放问题会自动解决，这也是最彻底的解决方案。

示例代码：

import WebKit

class YourViewController: UIViewController, WKNavigationDelegate {
    var webView: WKWebView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let webConfiguration = WKWebViewConfiguration()
        // 允许内联媒体播放
        webConfiguration.allowsInlineMediaPlayback = true
        // 允许自动播放（无需用户交互触发）
        webConfiguration.mediaTypesRequiringUserActionForPlayback = []
        
        webView = WKWebView(frame: self.view.frame, configuration: webConfiguration)
        webView.navigationDelegate = self
        view.addSubview(webView)
    }
    
    @IBAction func playVideo(_ sender: Any) {
        let frameHeight = self.view.frame.size.height // 替换为你实际的高度值
        let youtube_code = "YOUR_TARGET_VIDEO_ID" // 替换为你的YouTube视频ID
        
        let embededHTML = "<html><body style='margin:0px;padding:0px;'><script type='text/javascript' src='http://www.youtube.com/iframe_api'></script><script type='text/javascript'>function onYouTubeIframeAPIReady(){ytplayer=new YT.Player('playerId',{events:{onReady:onPlayerReady}})}function onPlayerReady(a){a.target.playVideo();}</script><iframe id='playerId' type='text/html' width='\(self.view.frame.size.width)' height=\(frameHeight) src='http://www.youtube.com/embed/\(youtube_code)?enablejsapi=1&rel=0&playsinline=1&autoplay=1&showinfo=0&modestbranding=0' frameborder='0'></body></html>"
        
        webView.loadHTMLString(embededHTML, baseURL: Bundle.main.bundleURL)
        self.view.bringSubview(toFront: webView)
        // 控制WKWebView的滚动属性
        webView.scrollView.isScrollEnabled = false
        webView.scrollView.bounces = false
    }
}

2. 监听YouTube播放器全屏状态，同步控制WebView滚动 #

问题的核心可能是：播放器还没完全完成退出全屏的流程时，界面滚动触发了AVPlayerViewController的错误调用。你可以通过YouTube的JS API监听全屏状态变化，通知原生代码调整滚动权限。

步骤1：修改HTML中的JS代码，添加全屏状态监听 #

function onYouTubeIframeAPIReady(){
    ytplayer=new YT.Player('playerId',{
        events:{
            onReady:onPlayerReady,
            onStateChange:onPlayerStateChange
        }
    })
}

function onPlayerStateChange(event) {
    // 监听全屏状态切换
    if (ytplayer.isFullscreen()) {
        // 进入全屏，通知原生禁止滚动
        window.webkit.messageHandlers.fullScreenChange.postMessage("enter");
    } else {
        // 退出全屏，延迟一点再允许滚动（确保播放器状态完全稳定）
        setTimeout(() => {
            window.webkit.messageHandlers.fullScreenChange.postMessage("exit");
        }, 300);
    }
}

步骤2：原生代码中接收JS通知，控制滚动 #

// 在viewDidLoad的WKWebView配置中添加消息处理器
webConfiguration.userContentController.add(self, name: "fullScreenChange")

// 实现WKScriptMessageHandler协议
extension YourViewController: WKScriptMessageHandler {
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        if message.name == "fullScreenChange", let status = message.body as? String {
            switch status {
            case "enter":
                webView.scrollView.isScrollEnabled = false
            case "exit":
                webView.scrollView.isScrollEnabled = true
            default: break
            }
        }
    }
}

3. 调整YouTube iframe参数 #

确保你的iframe URL中包含fs=1（明确允许全屏播放），同时确认playsinline=1参数正确设置，避免播放器状态异常。修改后的iframe src示例：

http://www.youtube.com/embed/\(youtube_code)?enablejsapi=1&rel=0&playsinline=1&autoplay=1&showinfo=0&modestbranding=0&fs=1

优先推荐第一种方案，因为WKWebView是苹果当前主推的Web组件，不仅能解决这个报错，还能提升整体性能和兼容性。

内容的提问来源于stack exchange，提问作者Jasur Rajabov