title: Flutter Dismissible in AnimatedList make animation twice
body: <p>I've an app with two rows in a AnimatedList and each row has a dismissible for remove item by swipe. 
  I'd noticed when you swipe a row for remove it then animation run twice.</p>
  
  <p>This is code:</p>
  
  <pre><code>  Widget _buildItem(BuildContext context, int index, Animation&lt;double&gt; animation) {
      Key k = new Key(_list[index]['item1'].toString());
      return Dismissible(
        key: k,
        background: Container(color: Colors.red),
        child:
        buildList(
          animation: animation,
          selected: _selectedItem == _list[index],
          item: _list[index],
        ),
        onDismissed: (direction) {
          _remove(index);
        },);
    }
  
    void _remove(int index) {
      _list.removeAt(index);
    }
  </code></pre>
  
  <p>How to fix that?</p>