How to create a gwt composite component with child

Question

I would like to create a component to decorate its children, such as:

mycomponent.ui.xml:

<g:FlowPanel addStyleNames="myStyle">
    <!-- how can i render children ? -->
</g:FlowPanel>

and then others can use:

<myapp:mycomponent>
    <g:Label>Decorated child</g:Label>
</myapp:mycomponent>

How can i render the children in uibinder? (or in Java, if i must)

Answer 1

Let MyComponent implement the HasWidgets interface for adding/removing child widgets.

The MyComponent.ui.xml looks as simple as

<g:FlowPanel ui:field="main" />

while you delegate the methods specified ind HasWidgets to the FlowPanel:

public class MyComponent extends Composite implements HasWidgets {

    private static MyComponentUiBinder uiBinder = GWT.create(MyComponentUiBinder.class);

    interface MyComponentUiBinder extends UiBinder<Widget, MyComponent> {}

    @UiField
    FlowPanel main;

    public MyComponent() {
        initWidget(uiBinder.createAndBindUi(this));
    }

    @Override
    public void add(Widget w) {
        main.add(w);
    }

    @Override
    public void clear() {
        main.clear();
    }

    @Override
    public Iterator<Widget> iterator() {
        return main.iterator();
    } 

    @Override
    public boolean remove(Widget w) {
        return main.remove(w);
    }
}

Calling

<M:MyComponent>
    <g:Label text="some text" />
</M:MyComponent>

will work this way.

Answer 2

Using this XML:

<myapp:mycomponent>
    <g:Label>Decorated child</g:Label> 
</myapp:mycomponent>

will instantiate MyComponent and then call MyComponent.add(label). All you have to do is override .add(..) in your class MyComponent and apply any styles that you want to passed components.