gl.setCaption("Change theme by clicking a button");
for (final String theme : new String[] { "reindeer", "runo",
"chameleon", "base", null }) {
Button b = new Button(theme);
b.setId(theme + "");
b.addClickListener(new ClickListener() {
@Override
public void buttonClick(ClickEvent event) {
getUI().setTheme(theme);
}