断言失败：第 235 行 pos 15：“数据！= null”：不正确

Question

尝试在标签栏中添加小部件时出现此错误。请检查以下代码

return Scaffold(
      appBar: new AppBar(
        bottom: PreferredSize(
            child: _tabBar,
            preferredSize: Size.fromHeight(_tabBar.preferredSize.height - 50),
        ),
      ),

      body:  new TabBarView(
        controller: _tabController,
        children: <Widget>[
          new PicMee(),
          new PicMee()
        ],
      ),
    );

对于 Picmee 文件：

class PicMee extends StatefulWidget{
  @override
  _PicMeeState createState() => new _PicMeeState();
}

    class _PicMeeState extends State<PicMee>{
      @override
      Widget build(BuildContext context) {
        // TODO: implement build
        return new Scaffold(
          body: new ListView.builder(
              itemCount: 20,
              itemBuilder: (BuildContext context, int index){
                return new CustomWidget(date: null, content: null, trailingIconOne: null, trailingIconTwo: null)
              }

    //          https://stackoverflow.com/questions/47233209/flutter-group-listviews-with-separator?rq=1
          ),
        );
      }
    }

    class CustomWidget extends StatelessWidget {
      String date;
      String content;

      Icon trailingIconOne;

      Icon trailingIconTwo;

      CustomWidget(
          {@required this.date, @required this.content, @required this.trailingIconOne, @required this.trailingIconTwo});

      @override
      Widget build(BuildContext context) {
        return new Container(
          decoration: new BoxDecoration(
              border: new Border.all(color: Colors.grey[500])
          ),
          child: new Column(
            children: <Widget>[
              new Container (child: new Text(date), color: Colors.yellow[200],),
              new Container(height: 15.0,),
              new Text(content),
              new Row(
                mainAxisAlignment: MainAxisAlignment.end,
                children: <Widget>[
                  new IconButton(icon: trailingIconOne, onPressed: () {}),
                  new Container(width: 10.0,),
                  new IconButton(icon: trailingIconTwo, onPressed: () {})
                ],
              )
            ],
          ),
        );
      }
    }

我收到此错误：

flutter：又抛出了一个异常：

'package:flutter/src/widgets/text.dart'：断言失败：第 235 行 pos 15: 'data != null': 不正确。

Answer 1

替换这一行：

return new CustomWidget(date: null, content: null, trailingIconOne: null, trailingIconTwo: null)

到这里：

return new CustomWidget(date: "date", content: "content", trailingIconOne: Icon(Icons.add), trailingIconTwo: Icon(Icons.add))