title: problems with setting parameters query objects
body: <p>Why <code>app.getElementById('myTextBox').setValue('default')</code> work in <code>showDialog()</code> but didnt work in <code>respondToSubmit(e)</code>?</p>
  
  <pre><code>function showDialog() {
    var app = UiApp.createApplication();
    var panel = app.createVerticalPanel();
  
    var textBox = app.createTextBox();
    textBox.setName('myTextBox').setId('myTextBox');
    app.getElementById('myTextBox').setValue('default');
  
    var button = app.createButton(Modify');
    panel.add(textBox);
    panel.add(button);
  
    var clickHandler = app.createServerClickHandler("respondToSubmit");
    button.addClickHandler(clickHandler);
    clickHandler.addCallbackElement(panel);
  
    app.add(panel);
    var doc = SpreadsheetApp.getActive();
    doc.show(app);
  }
  
  function respondToSubmit(e) {
    var app = UiApp.getActiveApplication();
    app.getElementById('myTextBox').setText('Modifed');
  }
  </code></pre>