ui bootstrap append dropdown-append-不起作用

Question

我具有带有ui-bootstrap下拉列表的代码：

 <div class="btn-group" style="float: right" uib-dropdown keyboard-nav dropdown-append-to="projectTreeBtn.add">
            <button type="button" class="btn btn-default projectTreeBtn" ng-click="deleteElement()"><span class="glyphicon glyphicon-remove"></span> Löschen</button>
            <button type="button" class="btn btn-default projectTreeBtn" id="projectTreeBtn.add"><span class="glyphicon glyphicon-plus"></span> Hinzufügen</button>
            <button type="button" class="btn btn-default projectTreeBtn" uib-dropdown-toggle><span class="caret"></span></button>
            <ul class="dropdown-menu" uib-dropdown-menu role="menu" aria-labelledby="projectTreeBtn.add">
                <li role="menuitem"><a href="#" ng-bind-html="menu.servicepackage"></a></li>
                <li role="menuitem"><a href="#" ng-bind-html="menu.projectphase"></a></li>
                <li role="menuitem"><a href="#" ng-bind-html="menu.servicemodular"></a></li>
                <li role="menuitem"><a href="#" ng-bind-html="menu.task"></a></li>
            </ul>
        </div>

我希望将下拉列表附加到第二个按钮上，但它始终显示为like this