Changing the title

MyViewImpl.java

public class MyViewImpl implements MyView, AttachEvent.Handler {
    interface Binder extends UiBinder<Widget, MyViewImpl> {}

    private final Widget widget;

    @Inject
    MyViewImpl(Binder binder) {
        widget = binder.createAndBindUi(this);
        widget.addAttachHandler(this);
    }

    @Override
    public void onAttachOrDetach(AttachEvent event) {
        if (event.isAttached()) {
            Document.get().setTitle("This is the new title of the page");
        }
    }

    // ...
}