I want to set value (number or string) to checkbox. This code

```
final CheckBox checkBox = new CheckBox("Some label");
checkBox.getElement().setAttribute("value", i.toString());
checkBox.getElement().getStyle().setProperty("color", colorList.get(i));
checkBox.addClickHandler(new ClickHandler() {
        @Override
        public void onClick(ClickEvent event) {
            Object sender = event.getSource();
            if (sender == checkBox) {
                CheckBox checkBox = (CheckBox)event.getSource();
                Window.alert(checkBox.getFormValue());
            }
        }
});

```

creates the following HTML:

```
<td align="left" style="vertical-align: top;">
<span class="gwt-CheckBox" value="3" style="color: rgb(128, 105, 155);">
<input id="gwt-uid-4" type="checkbox" value="on" tabindex="0">
<label for="gwt-uid-4">Some label</label>
</span>
</td>

```

The attribute `value` is set to `span` instead of `input`. The `Window.alert(checkBox.getFormValue())` shows message with string 'on', instead of '3'.