How to ADD a List<String> to CheckboxListTile values? - list

Question

On this example im trying to add to the CheckboxListTile the values i have saved on my List.
But for somereason im stuck here and i cant figure it out how to solve this problem.
Global List
List<String> _lstNomeData = new List<String>();
Values Map
Map<String, bool> values = {
'$_lstNomeData[index]': false,
};
Get selected checkbox values
var tmpArray = [];
getCheckboxItems() {
values.forEach((key, value) {
if (value == true) {
tmpArray.add(key);
}
});
print(tmpArray);
tmpArray.clear();
}
Body
body: Column(
children: <Widget>[
Expanded(
child: ListView(
children: values.keys.map((String key) {
return new CheckboxListTile(
title: new Text(key),
value: values[key],
activeColor: Colors.blue,
checkColor: Colors.white,
onChanged: (bool value) {
setState(() {
values[key] = value;
});
},
);
}).toList(),
),
),
],
)
Error
Print of the error displayed

Answer 1

You are on the right track. You can do two things here:
Prefill the map with false for every key (what you are trying to do)
Assume that if the map does not have a key, the answer is false (default)
Second approach is probably even better because by prefilling the map with false you could not distinct between false being actually answered by the user or if it was set by default. If a key is not in the map you know that the user has not answered the question so far. I will go and show how to work with the second approach:
Keep your global list as it is:
List<String> _lstNomeData = [];
Initialise the map (which represents the answers from the user for each question) with an empty Map:
Map<String, bool> answers = {};
Now correctly reference those answers in your Checkbox widget and make use of the onChanged property:
ListView(
children: _lstNomeData.map((key) =>
CheckboxListTile(
title: Text(key),
// Here we check if the answers map has this key and if it does, use the bool value, otherwise set it to false (user has not answered this so far)
value: answers[key] ?? false,
activeColor: Colors.blue,
checkColor: Colors.white,
onChanged: (answer) =>
setState(() => answers[key] = answer)
),
).toList(),
),