Wicket Retrieving A CheckGroup's model when clicking a checkbox

Question

I have a form with a checkbox column.

ArrayList<MyObject> myObjectsList = // Load from database ...
ArrayList<MyObject> selectedObjects = new ArrayList<MyObject>();

Form form = new Form("my-form");

CheckGroup<MyObject> myObjectGroup = new CheckGroup<MyObject>("object-check-group", new AbstractReadOnlyModel() {
  @Override
  public Object getObject() {
    return selectedObjects;
  }
});

WebMarkupContainer container = new WebMarkupContainer("table-container");

DataView dataView = new DataView("table-body", new ListDataProvider<MyObject>(myObjectsList)) {
  public void populateItem(final Item item) {
    final MyObject myObject = (MyObject) item.getModelObject();
    item.add(new Check("check-box", item.getModel())); // Checkbox for each item
    // And a couple more columns
  }
};

container.add(dataView);
group.add(container);
form.add(group);
add(form);

Now what I would want is to update a form whenever the number of selected objects change :

item.add(new Check("check-box", item.getModel()).add(new AjaxEventBehavior("onclick") {
  @Override
  protected void onEvent(AjaxRequestTarget target) {
    selectedObjects = (ArrayList<MyGroup>) myObjectGroup.getModelObject(); // this does not work sadly :(
    // Update form elements
  }
}));

Is there an easy way to achieve this with Wicket??

Answer 1

Add a AjaxFormChoiceComponentUpdatingBehavior to your checkgroup. The ajax will trigger everytime a check in your group is clicked.

    myObjectGroup.add(new AjaxFormChoiceComponentUpdatingBehavior() 
    {
        @Override
        protected void onUpdate(AjaxRequestTarget target) 
        {
            //update form elements  
        }         
    });