如何检测在 WKWebView 中播放的电影？

Question

我想知道是否可以检测到 WKWebView 中正在播放的电影？

另外我想知道打开的流的确切 URL？

Answer 1

由于这个问题的解决方案需要大量的研究和不同的方法，我想在这里记录它，以便其他人跟随我的想法。 如果您只是对最终解决方案感兴趣，请寻找一些花哨的标题。

我开始使用的应用程序非常简单。这是一个单视图应用程序，它导入 WebKit 并打开一个带有一些 NSURL 的 WKWebView：

import UIKit
import WebKit
class ViewController: UIViewController {
    var webView: WKWebView!

    override func viewDidAppear(animated: Bool) {
        webView = WKWebView()
        view = webView
        let request = NSURLRequest(URL: NSURL(string: "http://tinas-burger.tumblr.com/post/133991473113")!)
        webView.loadRequest(request) 
    }
}

该网址包含受（某种）JavaScript 保护的视频。 我真的还没有看过这个视频，这只是我发现的第一个视频。记得在你的Info.plist 中添加NSAppTransportSecurity 和NSAllowsArbitraryLoads，否则你会看到一个空白页。 p>

WKNavigationDelegate

WKNavigationDelegate 不会通知您正在播放的视频。所以设置webView.navigationDelegate = self 并实现协议不会给你带来想要的结果。

NSNotificationCenter

我假设一定有像SomeVideoPlayerDidOpen 这样的事件。不幸的是没有，但它可能有一个SomeViewDidOpen 事件，所以我开始检查视图层次结构：

UIWindow
    UIWindow
        WKWebView
            WKScrollView
            ...
        ...
UIWindow
    UIWindow
        UIView
            AVPlayerView
        UITransitionView
            UIView
                UIView
                    UIView
                        ...
                    UIView
                        ...
                    AVTouchIgnoringView
                        ...

正如预期的那样，将添加一个额外的UIWindow，可能有一个事件，是的，它确实有！

我通过添加一个新的观察者扩展了viewDidAppear:：

NSNotificationCenter.defaultCenter().addObserver(self, selector: "windowDidBecomeVisible:", name: UIWindowDidBecomeVisibleNotification, object: nil)

并添加了相应的方法：

func windowDidBecomeVisible(notification: NSNotification) {
    for mainWindow in UIApplication.sharedApplication().windows {
        for mainWindowSubview in mainWindow.subviews {
            // this will print:
            // 1: `WKWebView` + `[WKScrollView]`
            // 2: `UIView` + `[]`
            print("\(mainWindowSubview) \(mainWindowSubview.subviews)")
}

正如预期的那样，它返回了我们之前检查过的视图层次结构。但不幸的是，AVPlayerView 似乎稍后会创建。

如果您相信您的应用程序会打开唯一的UIWindow 是媒体播放器，那么您就完成了。但是这个解决方案不会让我晚上睡觉，所以让我们更深入......

注入事件

我们需要收到有关 AVPlayerView 被添加到这个无名 UIView 的通知。很明显AVPlayerView 必须是UIView 的子类，但由于Apple 没有正式记录它，我检查了iOS Runtime Headers for AVPlayerView，它肯定是UIView。

现在我们知道AVPlayerView 是UIView 的子类，它可能会通过调用addSubview: 添加到无名UIView。因此，我们必须收到有关已添加视图的通知。不幸的是，UIView 没有提供一个可以观察到的事件。但它确实调用了一个名为didAddSubview: 的方法，这可能非常方便。

所以让我们检查一下AVPlayerView 是否会添加到我们的应用程序的某个位置并发送通知：

let originalDidAddSubviewMethod = class_getInstanceMethod(UIView.self, "didAddSubview:")
let originalDidAddSubviewImplementation = method_getImplementation(originalDidAddSubviewMethod)

typealias DidAddSubviewCFunction = @convention(c) (AnyObject, Selector, UIView) -> Void
let castedOriginalDidAddSubviewImplementation = unsafeBitCast(originalDidAddSubviewImplementation, DidAddSubviewCFunction.self)

let newDidAddSubviewImplementationBlock: @convention(block) (AnyObject!, UIView) -> Void = { (view: AnyObject!, subview: UIView) -> Void in
    castedOriginalDidAddSubviewImplementation(view, "didAddsubview:", subview)

    if object_getClass(view).description() == "AVPlayerView" {
        NSNotificationCenter.defaultCenter().postNotificationName("PlayerWillOpen", object: nil)
    }
}

let newDidAddSubviewImplementation = imp_implementationWithBlock(unsafeBitCast(newDidAddSubviewImplementationBlock, AnyObject.self))
method_setImplementation(originalDidAddSubviewMethod, newDidAddSubviewImplementation)

现在我们可以观察通知并接收相应的事件：

NSNotificationCenter.defaultCenter().addObserver(self, selector: "playerWillOpen:", name: "PlayerWillOpen", object: nil)

func playerWillOpen(notification: NSNotification) {
    print("A Player will be opened now")
}

更好的通知注入

由于AVPlayerView 不会被删除而只会被释放，我们将不得不稍微重写我们的代码并向AVPlayerViewController 注入一些通知。这样我们就会有尽可能多的通知，例如：PlayerWillAppear 和 PlayerWillDisappear：

let originalViewWillAppearMethod = class_getInstanceMethod(UIViewController.self, "viewWillAppear:")
let originalViewWillAppearImplementation = method_getImplementation(originalViewWillAppearMethod)

typealias ViewWillAppearCFunction = @convention(c) (UIViewController, Selector, Bool) -> Void
let castedOriginalViewWillAppearImplementation = unsafeBitCast(originalViewWillAppearImplementation, ViewWillAppearCFunction.self)

let newViewWillAppearImplementationBlock: @convention(block) (UIViewController!, Bool) -> Void = { (viewController: UIViewController!, animated: Bool) -> Void in
    castedOriginalViewWillAppearImplementation(viewController, "viewWillAppear:", animated)

    if viewController is AVPlayerViewController {
        NSNotificationCenter.defaultCenter().postNotificationName("PlayerWillAppear", object: nil)
    }
}

let newViewWillAppearImplementation = imp_implementationWithBlock(unsafeBitCast(newViewWillAppearImplementationBlock, AnyObject.self))
method_setImplementation(originalViewWillAppearMethod, newViewWillAppearImplementation)

let originalViewWillDisappearMethod = class_getInstanceMethod(UIViewController.self, "viewWillDisappear:")
let originalViewWillDisappearImplementation = method_getImplementation(originalViewWillDisappearMethod)

typealias ViewWillDisappearCFunction = @convention(c) (UIViewController, Selector, Bool) -> Void
let castedOriginalViewWillDisappearImplementation = unsafeBitCast(originalViewWillDisappearImplementation, ViewWillDisappearCFunction.self)

let newViewWillDisappearImplementationBlock: @convention(block) (UIViewController!, Bool) -> Void = { (viewController: UIViewController!, animated: Bool) -> Void in
    castedOriginalViewWillDisappearImplementation(viewController, "viewWillDisappear:", animated)

    if viewController is AVPlayerViewController {
        NSNotificationCenter.defaultCenter().postNotificationName("PlayerWillDisappear", object: nil)
    }
}

let newViewWillDisappearImplementation = imp_implementationWithBlock(unsafeBitCast(newViewWillDisappearImplementationBlock, AnyObject.self))
method_setImplementation(originalViewWillDisappearMethod, newViewWillDisappearImplementation)

现在我们可以观察到这两个通知，一切顺利：

 NSNotificationCenter.defaultCenter().addObserver(self, selector: "playerWillAppear:", name: "PlayerWillAppear", object: nil)
NSNotificationCenter.defaultCenter().addObserver(self, selector: "playerWillDisappear:", name: "PlayerWillDisappear", object: nil)

func playerWillAppear(notification: NSNotification) {
    print("A Player will be opened now")
}

func playerWillDisappear(notification: NSNotification) {
    print("A Player will be closed now")
}

视频的网址

我花了几个小时挖掘一些 iOS 运行时标头来猜测在哪里可以找到指向视频的 URL，但我无法找到它。当我深入研究 WebKit 本身的一些源文件时，我不得不放弃并接受没有简单的方法可以做到这一点，尽管我相信它隐藏在某个地方并且可以到达，但很可能只有付出了很多努力。

Answer 2

我尝试将一些用户脚本添加（注入）到WKWebView，这种方式比方法调配安全一点：

相关代码如下：

let contentController = WKUserContentController()

if let jsSource = NSBundle.mainBundle().URLForResource("video_play_messenger", withExtension: "js"),
    let jsSourceString = try? String(contentsOfURL: jsSource) {
    let userScript = WKUserScript(source: jsSourceString, injectionTime: .AtDocumentEnd, forMainFrameOnly: true)

    contentController.addUserScript(userScript)
    contentController.addScriptMessageHandler(self, name: "callbackHandler")
}

let webConfiguration = WKWebViewConfiguration()
webConfiguration.userContentController = contentController

webView = WKWebView(frame: CGRect.zero, configuration: webConfiguration)
let request = NSURLRequest(URL: NSURL(string: "URL_FOR_VIDEO")!)
webView.loadRequest(request)

对于WKWebView的控制器，符合WKScriptMessageHandler并实现该方法：

func userContentController(userContentController: WKUserContentController, didReceiveScriptMessage message: WKScriptMessage) {
    if message.name == "callbackHandler" {
        if let messageString = message.body as? String where messageString == "VideoIsPlaying" {
            // Vide is being played
        }
    }
}

将video_play_messenger.js 添加到您的项目中：

function videoTags() {
    return document.getElementsByTagName("video");
}

function setupVideoPlayingHandler() {
    try {
        var videos = videoTags()
        for (var i = 0; i < videos.length; i++) {
            videos.item(i).onplaying = function() {
                webkit.messageHandlers.callbackHandler.postMessage("VideoIsPlaying");
            }
        }
    } catch (error) {
        console.log(error);
    }
}

function setupVidePlayingListener() {
    // If we have video tags, setup onplaying handler
    if (videoTags().length > 0) {
        setupVideoPlayingHandler();
        return
    }

    // Otherwise, wait for 100ms and check again.
    setTimeout(setupVidePlayingListener, 100);
}

setupVidePlayingListener();

参考：http://www.kinderas.com/technology/2014/6/15/wkwebview-and-javascript-in-ios-8-using-swift