如何在AngularJs ng-nestable插件中捕获拖动事件？

<div ng-nestable ng-model="list">
  <ul>
    <li ng-repeat="item in list" ng-nestable-item>
      {{ item.name }}
      <div ng-nestable-handle></div>
      <ol ng-nestable-list ng-model="item.children">
        <li ng-repeat="child in item.children" ng-nestable-item>
          {{ child.name }}
          <div ng-nestable-handle></div>
        </li>
      </ol>
    </li>
  </ul>
</div>

$scope.onDragStart = function(event, ui) {
  // 处理拖动开始事件
};

$scope.onDragStop = function(event, ui) {
  // 处理拖动停止事件
};

$scope.onDragMove = function(event, ui) {
  // 处理拖动移动事件
};

<div ng-nestable ng-model="list" ng-drag-start="onDragStart" ng-drag-stop="onDragStop" ng-drag-move="onDragMove">
  <!-- 列表内容 -->
</div>