WebView remote site and reward videos

I have a simple game developed in PHP. I have loaded the remote site in Android WebView. I want to find out that if user clicks on a FREE life button which is on my remote PHP site, I want to start a reward video on my Android app.

But how can I know whether the user clicked on the FREE life button in my WebView and start the video instantly in my android app?

There is an Android mechanism that alows you to run Android function from javascript:

        <input class="button" type="button" value="FREE life" onclick="startRewardVideo('some parameters can be passed to Android from here')">
            <script type="text/javascript">
                function startRewardVideo(paramFromJS) {
                    Android.startRewardVideoAndroidFunction(paramFromJS);
                }
            </script>

now you need class that knows what to do with your javascript:

public class MyJavaScriptInterface {

   @JavascriptInterface // this annotation is importatn
   public void startRewardVideoAndroidFunction(String paramFromJS) {

      //here you need to start showing reward movie 
      //because this function will be called after webView button click.
   }
}

last step is to connect webView with your javascript interface:

webView.addJavascriptInterface(new MyJavaScriptInterface(), "Android");

and of course don't forget to enable javascript for your webView:

webView.getSettings().setJavaScriptEnabled(true);

Hope it helps :) Ask if you have any questions on this.

Here you have full tutorial