test-gadget.xml

<?xml version="1.0" encoding="UTF-8" ?> 
<Module>
<ModulePrefs title="State Example" height="120">
  <Require feature="wave" /> 
</ModulePrefs>
<Content type="html">
<![CDATA[ 
<div id="content_div" style="height: 50px;"></div>
    <script type="text/javascript">

    var div = document.getElementById('content_div');

    function buttonClicked() {
      var value = parseInt(wave.getState().get('count', '0'));
      wave.getState().submitDelta({'count': value + 1});
    }

    function stateUpdated() {
      if(!wave.getState().get('count')) {
        div.innerHTML = "The count is 0."
      }
      else {
        div.innerHTML = "The count is " + wave.getState().get('count');
      } 
    }
 
    function init() {
      if (wave && wave.isInWaveContainer()) {
        wave.setStateCallback(stateUpdated);
      }
    }
    gadgets.util.registerOnLoadHandler(init);

    // Reset value of "count" to 0
    function resetCounter(){
      wave.getState().submitDelta({'count': '0'});
    }

    </script>
    <input type=button value="Click Me!" id="butCount" onClick="buttonClicked()">
    <input type=button value="Reset" id="butReset" onClick="resetCounter()">
  ]]> 
  </Content>
</Module>