@Override
public void onSelectionChange(final SelectionChangeEvent event) {
updateToolButtons();
}
});
DefaultCellBrowser cellBrowser = new DefaultCellBrowser.Builder(treeModel, null).build();
cellBrowser.setHeight("250px");
String add = principalType == Principal.Type.USER ? Console.CONSTANTS.role_assignment_add_user() : Console
.CONSTANTS.role_assignment_add_group();
String delete = principalType == Principal.Type.USER ? Console.CONSTANTS.role_assignment_delete_user() : Console
.CONSTANTS.role_assignment_delete_group();