The @JavascriptInterface annotation is required in Jelly Bean and later

If the target API level is JELLY_BEAN_MR1 (SDK version 17) or above, the interface object methods aren't visible to JavaScript unless the [@JavascriptInterface](http://developer.android.com/reference/android/webkit/JavascriptInterface.html) annotation is used.

See also [Binding JavaScript code to Android code](http://developer.android.com/guide/webapps/webview.html#BindingJavaScript) in the WebView documentation.