Select/deselect CheckBoxGroup via CheckBox

[listirer]

I have a CheckBoxGroup of some CheckBox and another CheckBox for select/deselect all CheckBox of CheckBoxGroup.
How can I implements this?
My code have some bug:

public class CheckBoxGroupExample extends LayoutContainer {

    private CheckBox a;
    private CheckBox b;
    private CheckBox c;
    private CheckBox all;

    @Override
    protected void onRender(Element parent, int index) {
        super.onRender(parent, index);

        CheckBoxGroup groupCheck = new CheckBoxGroup();
        groupCheck.setOrientation(Orientation.VERTICAL);

        a = new CheckBox();
        a.setBoxLabel("A");
        a.addListener(Events.Change, new Listener<FieldEvent>() {

            @Override
            public void handleEvent(FieldEvent fe) {
                manageAll();
            }
        });
        groupCheck.add(a);

        b = new CheckBox();
        b.setBoxLabel("B");
        b.addListener(Events.Change, new Listener<FieldEvent>() {

            @Override
            public void handleEvent(FieldEvent fe) {
                manageAll();
            }
        });
        groupCheck.add(b);

        c = new CheckBox();
        c.setBoxLabel("C");
        c.addListener(Events.Change, new Listener<FieldEvent>() {

            @Override
            public void handleEvent(FieldEvent fe) {
                manageAll();
            }
        });
        groupCheck.add(c);

        super.add(groupCheck);

        all = new CheckBox();
        all.setBoxLabel("Select/Deselect all");
        all.addListener(Events.Change, new Listener<FieldEvent>() {

            @Override
            public void handleEvent(FieldEvent fe) {
                Boolean checkedRaw = Boolean.valueOf(((CheckBox) fe.getField()).getRawValue());

                boolean allSelected = false;
                if (checkedRaw) {
                    allSelected = true;
                }

                a.setValue(allSelected);
                b.setValue(allSelected);
                c.setValue(allSelected);
            }
        });
        super.add(all);
    }

    private void manageAll() {
        if (a.getValue() && b.getValue() && c.getValue()) {
            all.setRawValue("true");
        } else {
            all.setRawValue("false");
        }
    }
}

Thanks

[listirer]

Problem fixed: I use setValue method disabling the firing change event for checkbox all, instead of setRawValue method.

The snipped code fix:

all.addListener(Events.Change, new Listener<FieldEvent>() {

    @Override
    public void handleEvent(FieldEvent fe) {
        Boolean allSelected = (Boolean) fe.getValue();

        a.setValue(allSelected);
        b.setValue(allSelected);
        c.setValue(allSelected);
    }
});

...

private void manageAll() {
    all..setFireChangeEventOnSetValue(false); // Disable the firing of Events.Change
    if (a.getValue() && b.getValue() && c.getValue()) {
        all.setValue(true);
    } else {
        all.setValue(false);
    }
    all.setFireChangeEventOnSetValue(true); // Enable the firing of Events.Change
}