@Override
public void handleEvent(Event evt) {
FileTreeSection files = testFileTree();
generated.<JsElement>cast().appendChild(files.getView().getElement());
files.getTree().renderTree(0);
Popup popup = Popup.create(resources);
popup.addPartner(generated.<JsElement>cast());
popup.setContentElement(files.getView().getElement());
popup.show(new PositionerBuilder()
.setVerticalAlign(VerticalAlign.BOTTOM)
.setPosition(Position.NO_OVERLAP)
.buildAnchorPositioner(generated.<JsElement>cast()));
}
}, true);