RangeError (index): Invalid value: Valid value range is empty: 0 in List Map

Question

In my app, I would like to have a listView with pie chart. This is the pie_chart library I'm using.

But I get error in List<Map<String,double>>.

List<Map<String, double>> map = List<Map<String, double>>();

 ListView.builder(
          physics: NeverScrollableScrollPhysics(),
          shrinkWrap: true,
          itemCount: data.length,
          itemBuilder: (context, index) {
            var item = data[index];
            map[index].putIfAbsent("< 1 Weeks ago>", () => (2.0));
            return PieChart(
                     ...
                dataMap: map[index],
                     ...
            )
    }

Error

RangeError (index): Invalid value: Valid value range is empty: 0

The error pointed to map[index].putIfAbsent("< 1 Weeks ago>", () => (2.0));. What is wrong here?

Answer 1

To add each of the elements from data and add them to map i did this:

  @override
  Widget build(BuildContext context) {
    List map = [];

    List data = [
      {'entry_1': 1},
      {'entry_2': 2},
      {'entry_3': 3}
    ];

    return MaterialApp(
      title: MyApp._title,
      home: Scaffold(
        body: ListView.builder(
          physics: NeverScrollableScrollPhysics(),
          shrinkWrap: true,
          itemCount: data.length,
          itemBuilder: (context, index) {
            var item = data[index];
            map.add(item);
            return Container(
              height: 100,
              child: Text('Entry: ${map[index]}'),
            );
          },
        ),
      ),
    );
  }

this takes the list of maps "data", grabs each value and add it to the list "map" and then builds a list of containers with a text widget containing the corresponding entry that map took from data