Flutter: How to map a list of maps? - flutter

Question

I have a very simple list of maps.
List<Map<String, String>> items = [
{ 'a': 'Some Text' },
{ 'b': 'Another Text' },
];
I want to map the above list to a dropdown list.
DropdownButton<String>(
hint: Text('Select a value'),
items: items.map((item) {
return DropdownMenuItem<String>(
value: // how to get key here a, b
child: // how to get value 'Some Text', 'Another Text'
);
}).toList(),
onChanged: (String newValue) {
setState(() {
// ...
});
},
),
)
How to get the key of the map, item has a property keys but not key and values and not value.

Answer 1

For this particular input:
List<Map<String, String>> items = [
{ 'a': 'Some Text' },
{ 'b': 'Another Text' },
];
You can do a workaround by accessing all the keys/values using getters and locating its very first element like this.
DropdownButton<String>(
items: items.map((item) {
return DropdownMenuItem<String>(
value: item.keys.first,
child: Text(item.values.first),
);
}).toList(),
onChanged: (value){},
)

Answer 2

You can copy paste run full code below
You need to use DropdownButton<Map<String, String>>
You can adjust Text("${value.keys.first} ${value.values.first}") per your request
code snippet
DropdownButton<Map<String, String>>(
value: dropdownValue,
icon: Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: TextStyle(color: Colors.deepPurple),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (Map<String, String> newValue) {
setState(() {
dropdownValue = newValue;
print(
"${dropdownValue.keys.first} ${dropdownValue.values.first}");
});
},
items: items.map<DropdownMenuItem<Map<String, String>>>(
(Map<String, String> value) {
return DropdownMenuItem<Map<String, String>>(
value: value,
child: Text("${value.keys.first} ${value.values.first}"),
);
}).toList(),
),
working demo
full code
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<Map<String, String>> items = [
{'a': 'Some Text'},
{'b': 'Another Text'},
];
Map<String, String> dropdownValue;
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
DropdownButton<Map<String, String>>(
value: dropdownValue,
icon: Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: TextStyle(color: Colors.deepPurple),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (Map<String, String> newValue) {
setState(() {
dropdownValue = newValue;
print(
"${dropdownValue.keys.first} ${dropdownValue.values.first}");
});
},
items: items.map<DropdownMenuItem<Map<String, String>>>(
(Map<String, String> value) {
return DropdownMenuItem<Map<String, String>>(
value: value,
child: Text("${value.keys.first} ${value.values.first}"),
);
}).toList(),
),
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}