WkWebKit - javascript on loaded page finds window.webkit is undefined

Question

I\'m experimenting with WkWebKit talking back and forth between app and page. I can get javaScript to execute fine using WkWebView evaluateJavascript method, but when I try

Answer 1

I solved it and problem was that if you set userContentController to a new object, that userContentController's WKScriptMessageHandlers will not be registered correctly in Apple's internal code:

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

fixed by using the already instantiated userContentController by Apple:

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

Answer 2

I ran into this SO because I was experiencing the same issue and this is how I solved it using a custom CustomContentController (subclass of WKUserContentController) instance.

let userContentController = CustomContentController()
let webViewConfiguration = WKWebViewConfiguration()
webViewConfiguration.userContentController = userContentController
webView = WKWebView(frame: .zero, configuration: webViewConfiguration)

In my case the CustomContentController is a subclass of WKUserContentController in which the add(_ scriptMessageHandler: WKScriptMessageHandler, name: String) method is called, but I don't believe that is significant.

I believe that the WKUserContentController must be instantiated and applied to a WKWebViewConfiguration before the WKWebView is initialized via WKWebView(frame: .zero, configuration: webViewConfiguration)

If the WKWebView has been created and then you try change the WKWebViewConfiguration you will encounter window.webkit not being available in the JSContext.

Answer 3

The window.webkit namespace only appears in webview with script message handlers. Make sure that you have called addScriptMessageHandler method of WKUserContentController.

Answer 4

I met the same problem. And after wasting 2 hours, I found this below to work fine. But I don't know why.

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    WKUserContentController *userCctrl = [[WKUserContentController alloc] init];
    [userCctrl addScriptMessageHandler:self name:@"jscall"];
    WKWebViewConfiguration *wbConfiger = [[WKWebViewConfiguration alloc] init];
    wbConfiger.userContentController = userCctrl;
    CGSize size = [UIScreen mainScreen].bounds.size;
    WKWebView *webView = [[WKWebView alloc] initWithFrame:CGRectMake(0, 20, size.width, size.height - 20)  configuration:wbConfiger];
    [self.view addSubview:webView];
    webView.UIDelegate = self;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [webView evaluateJavaScript:@"if (window.webkit === undefined) { alert('未注册的 window.webkit'); } else { window.webkit.messageHandlers.jscall.postMessage({title:'标题'}); }" completionHandler:^(id obj, NSError *error) {
            NSLog(@"run js completion with error = %@", error);
    }];
    });
}
#pragma mark -
- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(void))completionHandler {
    NSLog(@"run js alert panel message = %@", message);
    completionHandler();
}
#pragma mark -
- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message {
    NSLog(@"wkwebview run javascript name = %@, body = %@", message.name, message.body);
}