How to make a Grid occupy the rest of Tab's space

Hi all,

      I want to add a Grid to a Tab and make the Grid occupy the rest of Tab's space, but setExpandRatio(grid, 1f) does not work. The snapshot is attached.  Any help is appreciated.

p.s. I'm using Vaadin 7.6.6

Thanks in advance,
Daniel.Sun

TabSheet tabSheet = new TabSheet();
tabSheet.addTab(createIndexTab(request), "Index");

private VerticalLayout createIndexTab(VaadinRequest request) {
        VerticalLayout root = new VerticalLayout();
        root.setSizeFull();


        TextField textField = new TextField();
        textField.setWidth("100%");
        root.addComponent(textField);

        Grid grid = new Grid();
        grid.setWidth("100%");
        grid.setHeightMode(HeightMode.CSS);
        grid.setHeight("100%");

        grid.setSelectionMode(Grid.SelectionMode.SINGLE);
        grid.setHeaderVisible(false);

        grid.addColumn("item");

        for (int i = 0; i < 1000; i++) {
            grid.addRow("String" + i);
        }

        root.addComponent(grid);
        root.setExpandRatio(grid, 1f);

        root.setHeight("100%");

        return root;
    }