dart – Flutter – ListView中的DropdownButton溢出

Overflow of DropdownButton widget in ListView

代码是：

class DataInput extends StatefulWidget {

      @override
      State createState() => new DataInputState("");
    }


    enum DismissDialogAction {
      cancel,discard,save,}

    class DataInputState extends State<DataInput> {
      final String _data;
      static const types = const <Map<String,String>>[
        const {
          "id": "103","desc": "0001 - lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum lorem ipsum"
        },const {
          "id": "804","desc": "0002 - lorem ipsum lorem ipsum"
        },];

      DataInputState(this._data);

      @override
      Widget build(BuildContext context) {
        final ThemeData theme = Theme.of(context);
        return new Scaffold(
          appBar: new AppBar(
            title: const Text("Details"),actions: <Widget>[
              new FlatButton(
                  onPressed: () => Navigator.pop(context,DismissDialogAction.save),child: new Row(
                    children: <Widget>[
                      new Icon(Icons.save,color: Colors.white,),new Text(
                          "Save",style: theme.textTheme.body1.copyWith(
                            color: Colors.white,)
                      )
                    ],)
              ),],body: new ListView(
            shrinkWrap: true,children: <Widget>[
              new Text("Set Label"),new TextField(
                autocorrect: false,new Text("Select Type"),new Container(
                width: new FractionColumnWidth(0.5).value,child: new DropdownButton(
                    items: types.map((m) =>
                    new DropdownMenuItem(
                        key: new Key(m["id"]),child: new Text(m["desc"]))
                    ).toList(growable: false),onChanged: null
                ),);
      }
    }

错误：

══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
    The following message was thrown during layout:
    A horizontal RenderFlex overflowed by 433 pixels.

    The edge of the RenderFlex that is overflowing has been marked in the rendering with a yellow and
    black striped pattern. This is usually caused by the contents being too big for the RenderFlex.
    RenderFlex to fit within the available space instead of being sized to their natural size.
    This is considered an error condition because it indicates that there is content that cannot be
    seen. If the content is legitimately bigger than the available space,consider clipping it with a
    RectClip widget before putting it in the flex,or using a scrollable container rather than a Flex,for example using ListView.
    The specific RenderFlex in question is:
    RenderFlex#cc264 relayoutBoundary=up12 OVERFLOWING
    creator: Row ← SizedBox ← DefaultTextStyle ← Stack ← Listener ← _GestureSemantics ←
    RawGestureDetector ← GestureDetector ← DropdownButton ← ConstrainedBox ← Container ←
    RepaintBoundary-[<3>] ← ?
    direction: horizontal
    mainAxisAlignment: space-between
    mainAxisSize: min
    crossAxisAlignment: center
    textDirection: ltr
    verticalDirection: down

我尝试了以下方法,但它们不起作用：

>在行,列,填充和ClipRect中包含下拉列表

有人可以帮助我理解这一点,并说明如何解决它？

更新
使用FittedBox可以防止溢出,但文本大小会缩小到不可读.