<manifest package="com.example.sample">
    <queries>
        <package android:name="com.kakao.talk" />
    </queries>
    ...
</manifest>

webView = // main WebView

// common settings
webView.settings.run {
    javaScriptEnabled = true
    javaScriptCanOpenWindowsAutomatically = true
    setSupportMultipleWindows(true)
}

webView.webViewClient = object: WebViewClient() {

    override fun shouldOverrideUrlLoading(view: WebView,request: WebResourceRequest): Boolean {
        Log.d(TAG, request.url.toString())

        if (request.url.scheme == "intent") {
            try {
                // Create Intent
                val intent = Intent.parseUri(request.url.toString(), Intent.URI_INTENT_SCHEME)

                // run an app if there is an executable app.
                if (intent.resolveActivity(packageManager) != null) {
                    startActivity(intent)
                    Log.d(TAG, "ACTIVITY: ${intent.`package`}")
                    return true
                }

                // Load the WebView if there is Fallback URL
                val fallbackUrl = intent.getStringExtra("browser_fallback_url")
                if (fallbackUrl != null) {
                    view.loadUrl(fallbackUrl)
                    Log.d(TAG, "FALLBACK: $fallbackUrl")
                    return true
                }

                Log.e(TAG, "Could not parse anythings")

            } catch (e: URISyntaxException) {
                Log.e(TAG, "Invalid intent request", e)
            }
        }

        // Implement the rest logic for a service.

        return false
    }
}

webView = // Main WebView
webViewLayout = // The layout that the WebView is included

// Common settings
webView.settings.run {
    javaScriptEnabled = true
    javaScriptCanOpenWindowsAutomatically = true
    setSupportMultipleWindows(true)
}

webView.webChromeClient = object: WebChromeClient() {

    /// ---------- Open pop-up  ----------
    /// - Use a pop-up for Kakao Login in the JavaScript SDK.
    /// - Must create a seperate WebView when calling window.open()
    ///
    override fun onCreateWindow(
        view: WebView,
        isDialog: Boolean,
        isUserGesture: Boolean,
        resultMsg: Message
    ): Boolean {

        // Create a WebView
        var childWebView = WebView(view.context)

        // Set the same WebView as a parent WebView.
        childWebView.run {
            settings.run {
                javaScriptEnabled = true
                javaScriptCanOpenWindowsAutomatically = true
                setSupportMultipleWindows(true)
            }
            layoutParams = view.layoutParams
            webViewClient = view.webViewClient
            webChromeClient = view.webChromeClient
        }

        // Add a WebView to the layout
        webViewLayout.addView(childWebView)
        // TO DO: It is recommended to manage a seperate WebView
        //       to handle navigation action of users
        //       such as onBackPressed() besides adding a layout.
        //   ex) childWebViewList.add(childWebView)

        // Syncronize between WebViews
        val transport = resultMsg.obj as WebView.WebViewTransport
        transport.webView = childWebView
        resultMsg.sendToTarget()

        return true
    }

    /// ---------- Close a pop-up  ----------
    /// - Must close the created WebView when window.close() is called.
    ///
    override fun onCloseWindow(window: WebView) {
        super.onCloseWindow(window)

        // Remove a pop-up from the layout
        webViewLayout.removeView(window)
        // TO DO: It is recommended to manage a seperate WebView array
        //       to handle navigation action of users
        //       such as onBackPressed() besides adding a layout.
        //   ex) childWebViewList.remove(childWebView)
    }
}

func webView(_ webView: WKWebView,
             decidePolicyFor navigationAction: WKNavigationAction,
             decisionHandler: @escaping (WKNavigationActionPolicy) -> Void
) {
    print(navigationAction.request.url?.absoluteString ?? "")

    // If the Custom URL Scheme is invoked, open(_ url:) is called.
    if let url = navigationAction.request.url , ["kakaolink"].contains(url.scheme) {

        // If the system can handle the url, Kakao Talk is launched.
        if UIApplication.shared.canOpenURL(url) {
            UIApplication.shared.open(url, options: [:], completionHandler: nil)
        }

        decisionHandler(.cancel)
        return
    }

    // Implement the rest logic for your service.


    decisionHandler(.allow)
}

class ViewController: UIViewController, WKUIDelegate, WKNavigationDelegate {

    // Manage a list of WebViews
    var webViews = [WKWebView]()

    ...

    /// ---------- Open pop-up  ----------
    /// - Use a pop-up for Kakao Login in the JavaScript SDK.
    /// - Must create a seperate WebView when calling window.open()
    ///
    func webView(_ webView: WKWebView,
                 createWebViewWith configuration: WKWebViewConfiguration,
                 for navigationAction: WKNavigationAction,
                 windowFeatures: WKWindowFeatures
    ) -> WKWebView? {
        guard let frame = self.webViews.last?.frame else {
            return nil
        }

        // If creating a WebView and returning the WebView, the WebView becomes a child of the current WebView as a parent
        return createWebView(frame: frame, configuration: configuration)
    }

    /// ---------- Close a pop-up  ----------
    /// - Must close the created WebView when window.close() is called.
    ///
    func webViewDidClose(_ webView: WKWebView) {
        destroyCurrentWebView()
    }

    // An example of methods to create a WebView
    func createWebView(frame: CGRect, configuration: WKWebViewConfiguration) -> WKWebView {
        let webView = WKWebView(frame: frame, configuration: configuration)

        // Set delegate
        webView.uiDelegate = self
        webView.navigationDelegate = self

        // Add to the layout
        self.view.addSubview(webView)

        // Add to the list of WebViews
        self.webViews.append(webView)

        // Add other views to optimize for a service environment


        return webView
    }

    // an example of methods to delete a WebView
    func destroyCurrentWebView() {
        // Remove a WebView from the layout abd list of WebViews
        self.webViews.popLast()?.removeFromSuperview()
    }

}