js调用原生webview

// Android原生代码
public class WebAppInterface {
    Context mContext;

    WebAppInterface(Context c) {
        mContext = c;
    }

    @JavascriptInterface
    public void showToast(String toast) {
        Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show();
    }
}

WebView webView = (WebView) findViewById(R.id.webview);
webView.getSettings().setJavaScriptEnabled(true);
webView.addJavascriptInterface(new WebAppInterface(this), "Android");
webView.loadUrl("file:///android_asset/index.html");

<!-- HTML中的JavaScript代码 -->
<script type="text/javascript">
    function showAndroidToast(toast) {
        Android.showToast(toast);
    }
</script>

// iOS原生代码
import WebKit

class ViewController: UIViewController, WKScriptMessageHandler {
    override func viewDidLoad() {
        super.viewDidLoad()

        let webView = WKWebView(frame: self.view.frame)
        self.view.addSubview(webView)

        let contentController = WKUserContentController()
        contentController.add(self, name: "nativeHandler")

        let config = WKWebViewConfiguration()
        config.userContentController = contentController

        webView.configuration = config
        webView.load(URLRequest(url: URL(string: "http://yourdomain.com")!))
    }

    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        if message.name == "nativeHandler", let messageBody = message.body as? String {
            print("Received message from JS: \(messageBody)")
        }
    }
}

<!-- HTML中的JavaScript代码 -->
<script type="text/javascript">
    function sendMessageToNative(message) {
        window.webkit.messageHandlers.nativeHandler.postMessage(message);
    }
</script>