Handle webkit.messageHandler postMessage on Android

Question

I tried to execute code in android from the web view through events. So I implemented the good way with a JavascriptInterface, but since I have a iOS Application, I wanted to use the same method. So is this possible to use the message handler on Android (just a simple JS event) rather than the Bridging of the interface ? I also tried to the other way : Make a bridge on iOS the same way of Android, but it doesn't work with WKWebview (but it's another problem) Thanks !

Answer 1

This is not recommended, if you have the option to change your JS-code and add a conditional handler, you should do that instead.

If you have implemented a handler in iOS using userContentController and want to reuse it in Android, you can inject JS to replace the window.webkit.messageHandlers property with your android equivalent.

Say this is your swift code:

webView.configuration.userContentController.add(self, name: "iosListener")

func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
  //handle message
}

And your JS code:

window.webkit.messageHandlers.iosListener.postMessage("some message")

You can reuse it in android/kotlin without changing your JS code like this:

inner class MyJsInterface() {

    @JavascriptInterface
    fun postMessage(value: String) {
        //handle message
    }
}

webView.run {
    settings.javaScriptEnabled = true
    addJavascriptInterface(MyJsInterface(), "AndroidListener")
    webViewClient = object : WebViewClient() {
        override fun onPageStarted(view: WebView?, url: String?, favicon: Bitmap?) {
            super.onPageStarted(view, url, favicon)
            evaluateJavascript("window.webkit = { messageHandlers: { iosListener: window.AndroidListener} }") {}
        }
    }
}