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Flutter – How to fix error data table 'columns.isNotEmpty': is not true

I am using flutter datatable.

I am using List<DataColumn> and List<DataRow>.

After I click a button, I need to see the table populated.

I am getting the error during runtime: 'columns.isNotEmpty' is not true

I cannot find the source of the error.

Please advise how to fix the error.

Thank You,

This is my code:

class MyHomePageState extends State<MyHomePage> {
  List<DataColumn> myDataColumnList = [];
  List<DataRow> myDataRowList = [];
  int i = 0;

  @override
  void initState() {
    super.initState();
  }

  addToList(){
   setState(() {
     myDataColumnList.add(DataColumn(label: Text('Column Label: '+i.toString())));
     myDataRowList.add(DataRow(cells: <DataCell>[DataCell(placeholder: true,Text('x1: '+i.toString())),DataCell(placeholder: true,Text('x2: '+i.toString()))]));
     i = i + 1;
   });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: Scaffold(resizeToAvoidBottomInset: true,
        body: LayoutBuilder(
            builder: (BuildContext ctx, BoxConstraints constraints) {
              return Container(child: SingleChildScrollView(child: Column(mainAxisAlignment: MainAxisAlignment.spaceEvenly,mainAxisSize: MainAxisSize.min,
                children: <Widget>[
                  TextButton(onPressed: addToList, child: const Text('addToList')),
                  Table(children: [TableRow(children: <Widget>[ListView.builder(shrinkWrap: true,itemBuilder: (BuildContext context, int index) {
                    return DataTable(columns: myDataColumnList, rows: myDataRowList);
                  },)])]),],),),);
            })));
  }
}
Tags:

2

Answers


  1. 0

    Remove updating myDataColumnList in setState method,

    addToList() {
    setState(() {
      // myDataColumnList
      //     .add(DataColumn(label: Text('Column Label: ' + i.toString())));
      myDataRowList.add(DataRow(cells: <DataCell>[
        DataCell(placeholder: true, Text('x1: ' + i.toString())),
        DataCell(placeholder: true, Text('x2: ' + i.toString()))
      ]));
      i = i + 1;
    });   
}

    Instead, you can initialize your myDataColumnList in initstate

    Try something like:

    return Scaffold(
      resizeToAvoidBottomInset: true,
      body: SingleChildScrollView(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          TextButton(onPressed: addToList, child: const Text('addToList')),
          DataTable(
            columns: [
              ///Create your column list in initstate and use it here
              DataColumn(label: Text('Column Label: 1')),
              DataColumn(label: Text('Column Label: 2')),
            ],
            rows: myDataRowList,
          ),
        ],
      ),
    ),
   );
    Login or Signup to reply.
  2. 0

    Add this condition to avoid the error the first time you run the app.

    if (myDataColumnList.isNotEmpty)
  Table(children: [
   ....
   ]),
    Login or Signup to reply.
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