Communication between Android Java and Phonegap Javascript?

I finally made it work.

• Create a class with methods you want to use:

  public class MyClass {
    private WebView mAppView;
    private DroidGap mGap;
  
    public MyClass(DroidGap gap, WebView view)
    {
      mAppView = view;
      mGap = gap;
    }
  
    public String getTelephoneNumber(){
      TelephonyManager tm = 
        (TelephonyManager) mGap.getSystemService(Context.TELEPHONY_SERVICE);
      String number = tm.getLine1Number();
      return number;
    }
  }
  

• In your main activity add a Javascript interface for this class:

  public class Main extends DroidGap
  {
      private MyClass mc;
  
      @Override
      public void onCreate(Bundle savedInstanceState)
      {
          super.onCreate(savedInstanceState);
          super.init();
  
          mc = new MyClass(this, appView);
          appView.addJavascriptInterface(mc, "MyCls");
  
          super.loadUrl(getString(R.string.url));
      }
  }
  

• In Javascript call window.MyCls methods:

  <script>
    $(function(){
      $("#phone").text("My telephone number is: " + 
              window.MyCls.getTelephoneNumber());
    });
  </script>
  

Note:

As mentioned in the comment, for Android version 4.2 and above, add @JavascriptInterface to the method which you want to access from your HTML page. Reference.