how do you map index value to text for dropdownButton - flutter

Question

In flutter I how do you map index to string. Example I have a List for numbers. I want to display text and capture the value in the back ground that would be numbers. I am using Dropdown menu item but you can only pass one value.
final List nums = ['1', '2', '3','4','5', '6',]
DropdownButton(
items: nums.map((e) {
return DropdownMenuItem(
value: e,
child: Text(e));
}).toList(),
);
I want to do something like:
final List nums = ['1': 'one', '2': 'two', '3': 'three','4': 'four','5': 'five', '6': 'six'];
i represent the number
e represent the text
DropdownButton(
items: nums.map((i, e) {
return DropdownMenuItem(
value: i,
child: Text(e));
}).toList(),
);

Answer 1

You could use the dropdown as here :
final Map nums = ['1': 'one', '2': 'two', '3': 'three','4': 'four','5': 'five', '6': 'six'];
String dropdownValue = nums["one"]; //set the dropdown's default value
DropdownButton(
value: dropdownValue,
onChanged: (String newValue) {
setState(() {
dropdownValue = nums[newValue]; //update the dropdown's value
});
},
items: nums.map((i, e) {
return DropdownMenuItem(
value: i,
child: Text(e));
}).toList(),
);

Answer 2

To capture the index or incremental value for the the string value. You should use indexof. Here is an example:
final List nums = ['one', 'two', 'three','four', 'five', 'six'];
int dropdownValue;
DropdownButton(
onChanged: (String newValue) {
setState(() {
dropdownValue = nums.indexOf(newValue) + 1;
});
},
items: nums.map((e) {
return DropdownMenuItem(
value: i,
child: Text(e));
}).toList(),
);