javascript - WkWebKit - 加载页面上的 javascript 发现 window.webkit 未定义

Question

我正在试验 WkWebKit 在应用程序和页面之间来回对话。我可以使用 WkWebView evaluateJavascript 方法让 javaScript 正常执行，但是当我尝试在 JavaScript 页面上执行 window.webkit.messageHandlers.myHandler.postMessage('hello world!') 时，我发现 window.webkit 没有定义。

奇怪...我在 iOS 8.4 的 iPad 模拟器中运行。我以为这在原始版本 8 中可用，不是吗？

我找不到其他人发帖，所以也许我做错了什么？

我什至将我的 Safari Developer 附加到模拟器的浏览器，并在控制台中尝试查看 window.webkit 是什么，果然，它不存在。

请注意，我添加了一个初始脚本以在页面加载时运行(我在 javascript 编辑器中看到了这一点 - 消息已记录)。我还添加了一个脚本消息处理程序...

[编辑:在此处添加更多代码细节]这是我的代码:

- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  NSLog(@"main view Controller viewDidLoad called...");

// if we are running on an OLD ios (pre v8) WKWebView will not exist.  So don't create it if it doesn't exist...
if (NSClassFromString(@"WKWebView")) {
    // WKWebView cannot be dragged onto storyboard, so have to create it manually here.
    // We have a "ContainerView" called _webContainer that this browser view will live inside
    // First we create a web view configuration object...
    WKWebViewConfiguration *wbConfig = [WKWebViewConfiguration alloc];
    wbConfig.mediaPlaybackAllowsAirPlay = true;
    wbConfig.mediaPlaybackRequiresUserAction = false; 
    // inject some Javascript into our page before it even loads...
    NSString *scriptSource = @"console.log('Hi from the iOS app hosting this page...'); window.hostedByWkWebView=true;";
    WKUserScript *userScript = [[WKUserScript alloc]
                                initWithSource:scriptSource
                                injectionTime:WKUserScriptInjectionTimeAtDocumentStart
                                forMainFrameOnly:YES];

    [wbConfig.userContentController addUserScript:userScript];
    [wbConfig.userContentController addScriptMessageHandler:self name:@"myHandler"]; // javascript to use this would be: window.webkit.messageHandlers.myHandler.postMessage


    // Ok, the config is created, now create the WkWebView instance, passing in this config...
    _webView = [[WKWebView alloc] initWithFrame: [_webContainer bounds] configuration:wbConfig];
    _webView.autoresizesSubviews = true;
    _webView.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight;
    _webView.navigationDelegate = self;

    // Add the web view to the container view, and tell the container to automatically resize its subviews, height and width.
    [_webContainer addSubview:_webView];
    _webContainer.autoresizesSubviews = true;
    _webContainer.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight;

    // Set the URL for the webview and navigate there...
    NSString *fullURL = @"https://myurlgoeshere.com";

    NSURL *url = [NSURL URLWithString:fullURL];
    NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];

    [_webView loadRequest:requestObj];
}
else {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Cannot create Web View" message:@"The web view used requires iOS 8 or higher.  Sorry." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:@"", nil];
    [alert show];
}

//...

Answer 1

我解决了它，问题是如果你将 userContentController 设置为一个新对象，那么 userContentController 的 WKScriptMessageHandler 将不会被注册在 Apple 的内部代码中正确:

WKUserContentController *userContentController = [WKUserContentController new];
userContentController.addScriptMessageHandler(self, name: "jockey")
userContentController.addScriptMessageHandler(self, name: "observe")
webView.configuration.userContentController = userContentController

通过使用 Apple 已经实例化的 userContentController 修复:

webView.configuration.userContentController.addScriptMessageHandler(self, name: "jockey")
webView.configuration.userContentController.addScriptMessageHandler(self, name: "observe")