Android 4.2.1, WebView and javascript interface breaks

Question

I have a webview with added javascript interface which works perfectly on most devices, except for those running Android 4.2.1.

I removed most of the code, and stayed with a very basic code:

this.webView.getSettings().setJavaScriptEnabled(true);
this.webView.setWebChromeClient(new WebChromeClient());
this.webView.addJavascriptInterface(new Object() {
    public void handshake() {
        Log.d("JS", "handshake no params");
    }

    public void handshake(String json) {
        Log.d("JS", "handshake with params: " + json);
    }
}, "Android");

In the javascript side of things the testing code looks like this:

Android.handshake();

But I get this in the logcat:

E/Web Console: Uncaught TypeError: Object [object Object] has no method 'handshake'

Again, this same exact thing works fine in devices who are have older android os (< 4.2.1) that I have tested (the minimal version being 2.3.3).

The strange thing is that if I start a completely new project, with nothing but a single Activity which has just a WebView, with the same code, everything works fine even for 4.2.1, but when it's part of my actual project, things break. There's nothing I'm doing with the webview which is not included in this code snippets I provided.

What is the most strange to me is that the javascript finds the Android object but it just does not have the requested method (handshake), how can that be?

Any help will be greatly appreciated since this has been driving me crazy for the past 2 weeks or so (it's a bug I go back to all the time, then give up, etc). Thanks.

Answer 1

From the Android 4.2 documentation:

Caution: If you've set your targetSdkVersion to 17 or higher, you must add the @JavascriptInterface annotation to any method that you want available your web page code (the method must also be public). If you do not provide the annotation, then the method will not accessible by your web page when running on Android 4.2 or higher.