[Flutter]使用Dismissible组件实现滑动删除过程遇到“A dismissed Dismissible widget is still part of the tree.”

freddon 发表于2019-08-12   阅读 2337 | 评论 0

“滑动删除”模式,在ListItem组件外层包裹Dismissible组件,滑动删除操作后,报错: A dismissed Dismissible widget is still part of the tree.
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。

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