How to solve problem with null values in column? - flutter

Question

This is the problem:
Column's children must not contain any null values, but a null value was found at index 0
I think it has something to do with the map, but i am not sure.
I am quite new to coding with dart so any help would be appreciated.
And here is the code:
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
home: Main(),
));
int counter = 0;
class Main extends StatefulWidget {
#override
_MainState createState() => _MainState();
}
class _MainState extends State<Main> {
static List<String> names = [
'name1',
'name2',
];
static List<String> difficulty = [
'easy',
'normal',
];
String currentDifficulty = difficulty[counter];
var count = names.length;
#override
Widget build(BuildContext context) {
return Container(
child: Column(
children: names.map((name) {
Container(
child: Column(
children: <Widget>[
Text(
name
),
Text(
'currentDifficulty'
),
],
),
);
counter += 1;
}).toList(),
),
);
}
}

Answer 1

If you want to know the index of each widget you are creating on a map function from a list I would suggest to use List.asMap().map((index, string)=> MapEntry(index, widget())).values.toList() since the map function alone does not allow to get the index
Try substituting your children code for:
names.asMap().map((index, name)=> MapEntry(index, Container(
child: Column(
children: <Widget>[
Text(
name
),
Text(
difficulty[index]
),
],
),
))).values.toList();

Answer 2

You are getting the errors because:
1) You are accessing the elements of your List wrongly. To access elements in a List, use the elementAt method
2) The children property of your Column is missing a return statement .
3) Instead of using a counter to iterate through the second list. You can map through the two lists using the IterableZip.
Check the code below: It solves the errors and it works fine
int counter = 0;
class MyHomePage extends StatelessWidget {
static List<String> names = [
'name1',
'name2',
];
static List<String> difficulty = [
'easy',
'normal',
];
// access elements in a list using the elementAt function
String currentDifficulty = difficulty.elementAt(counter);
#override
Widget build(BuildContext context) {
names.map((e) => print(e));
return Scaffold(
body: Center(
child: Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
// map the two lists using IterableZip and passing the two lists
children: IterableZip([names, difficulty]).map(
(element) {
// missing return statement
return Container(
child: Column(
children: <Widget>[
// access elements of your first list here
Text(element[0]),
// access elements of your second list here
Text(element[1]),
],
),
);
},
).toList(),
),
),
),
);
}
}
OUTPUT
I hope this helps.