核心代码如下： __ListItem：__ ``` Widget _itemView(Unit item) => ListTile( title: Text( item.name, style: TextStyle( color: Colors.black, fontWeight: FontWeight.w700, fontSize: 17.0), ), leading: ClipRRect( borderRadius: BorderRadius.circular(12.0), child: Image.asset( 'assets/icon/' + item.icon, width: 48, height: 48, )), trailing: Icon( Icons.chevron_right, color: Colors.orange, size: 24, ), ); ``` __Dismissble部分：__ ``` Dismissible( key: new Key(item.name), background: new Container(color: Colors.red), secondaryBackground: Container( color: Colors.green, ), child: _itemView(item), onDismissed: (direction) { removeItem(item); }) ``` 如上所示，没一个ListItem绑定的对象为Unit类型，至少有`name`、`icon`属性。 当执行滑动删除时，报错如下： ``` flutter: ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ flutter: The following assertion was thrown building Dismissible-[<'DNF'>](dirty, dependencies: flutter: [Directionality], state: _DismissibleState#c1bbf(tickers: tracking 2 tickers)): flutter: A dismissed Dismissible widget is still part of the tree. flutter: Make sure to implement the onDismissed handler and to immediately remove the Dismissible flutter: widget from the application once that handler has fired. ``` 即：__`该widget并未从节点中移除`__ 排查步骤： 1. 检查`removeItem(item);`方法，排查是否从提供的数据源中移除该条目； 2. 检查item对象`（Unit）`的Key是否唯一。即： ``` Dismissible( key: new Key(item.name), //.... ) ``` 果然，item.name在本例中会重复，采用`new ObjectKey(item)`或`new Key(item.id)`即可。 以上。