Checking Internet Connection using SmartGWT or GWT?

Question

How can we check if there is Internet connectivity in the application or not in SmartGWT or GWT? I have to determine that whether there is internet connection or not and based on that change the icon for Internet connectivity to either green or red so is there a way to do it in SmartGWT or GWT?

Answer 1

You can create a native method in which you create a new image object (new Image()) and attach handler to it's onload and onerror properties. You can point the image's src property to some URL that you feel indicates being online. Then from your onload and onerror methods you can call methods in your GWT component to update your connectivity indicator. You need to set img.src after you set img.onload and img.onerror.

For example:

native void checkConnectivity(Example obj) /*-{
    var img = new Image();
    img.onload = function() {           
      obj.@com.example.client.Example::online()();
    }
    img.onerror = function() {                    
      obj.@com.example.client.Example::offline()();
    }
    img.src = "http://exampleapp.com/test.gif";
}-*/;