如何强制 WKWebView 忽略 iOS 上的硬件静音开关？

Question

这里的要求是不管硬件静音开关如何播放各种网络声音，静音和未静音设备都必须在应用程序处于前台时继续在 HTML 页面中播放声音。deprecated 的解决方案UIWebView很简单

let localWebView = UIWebView(frame: .zero)
localWebView.allowsInlineMediaPlayback = true
localWebView.mediaPlaybackRequiresUserAction = false

如何实现相同的行为WKWebView？

Answer 1

既然我有这个非平凡问题的解决方案，我想分享一下：

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(didBecomeActive),
                                               name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(willResignActive),
                                               name: NSNotification.Name.UIApplicationWillResignActive, object: nil)
    let configuration = WKWebViewConfiguration()
    configuration.allowsInlineMediaPlayback = true
    configuration.mediaTypesRequiringUserActionForPlayback = []
    wkWebView = WKWebView(frame: .zero, configuration: configuration)
}

@objc func willResignActive() {
    disableIgnoreSilentSwitch(wkWebView)
}

@objc func didBecomeActive() {
    //Always creates new js Audio object to ensure the audio session behaves correctly
    forceIgnoreSilentHardwareSwitch(wkWebView, initialSetup: false)
}   

最重要的是WKNavigationDelegate：

private func disableIgnoreSilentSwitch(_ webView: WKWebView) {
    //Nullifying the js Audio object src is critical to restore the audio sound session to consistent state for app background/foreground cycle
    let jsInject = "document.getElementById('wkwebviewAudio').src=null;"
    webView.evaluateJavaScript(jsInject, completionHandler: nil)
}

private func forceIgnoreSilentHardwareSwitch(_ webView: WKWebView, initialSetup: Bool) {
    //after some trial and error this seems to be minimal silence sound that still plays
    let silenceMono56kbps100msBase64Mp3 = "data:audio/mp3;base64,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"
    //Plays 100ms silence once the web page has loaded through HTML5 Audio element (through Javascript)
    //which as a side effect will switch WKWebView AudioSession to AVAudioSessionCategoryPlayback

    var jsInject: String
    if initialSetup {
        jsInject = "var s=new Audio('\(silenceMono56kbps100msBase64Mp3)');s.id='wkwebviewAudio';s.controls=false;s.loop=true;s.play();document.body.appendChild(s)"
    } else {
        jsInject = "var s=document.getElementById('wkwebviewAudio');s.src=null;s.parentNode.removeChild(s);s=null;s=new Audio('\(silenceMono56kbps100msBase64Mp3)');s.id='wkwebviewAudio';s.controls=false;s.loop=true;s.play();document.body.appendChild(s)"
    }
    webView.evaluateJavaScript(jsInject, completionHandler: nil)
}

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    //As a result the WKWebView ignores the silent switch
    forceIgnoreSilentHardwareSwitch(webView, initialSetup: true)
}

有趣的是，这里提到了一个相关的 Safari 问题：IOS WebAudio 仅适用于@Spencer Evans 解决方法与我的非常相似的耳机。

然而，当我尝试应用他较短的 base64 静音声音时，它不起作用WKWebView，所以我提供了我自己在 iOS12 上测试的最小静音声音。

为什么有效？

播放<audio>或<video>元素（在变通方法中恰好是听不见的静音）将WKWebView音频会话类别从更改AVAudioSessionCategoryAmbient为AVAudioSessionCategoryPlayback。这将一直有效，直到下一个加载请求将其重置。

一切都很好，直到应用程序成为后台。但是在随后的前景化过程中，事情会以两种可能的方式中断：

• 用户需要点击声音才能重新出现
• 很少有用户输入会有所帮助，并且 WKWebView 处于半冻结状态

为了解决这个问题^ hack被恢复，disableIgnoreSilentSwitch(wkWebView)然后重新启用forceIgnoreSilentHardwareSwitch(wkWebView, initialSetup: false)

由于WKWebView核心在外部进程中运行，因此无法像UIWebView共享（与我们的应用程序）那样访问它AVAudioSession。

已针对 iOS 11.4 - 13.3 进行验证