How to build dropdown list from future in flutter - flutter

Question

i want to build Dropdown list from Future,here is my function for simple list view which is working,,but how to populate drop down list from it, i am really confuse about this list map etc in flutter coming from php background,
child: FutureBuilder(
future:userApi.getUsers(),
builder: (BuildContext context, AsyncSnapshot snapshot){
if(snapshot.data == null){
return Container(
child: Center(
child: Text("Loading...")
)
);
} else {
return Container(
child: DropdownButton(
items: snapshot.data.map((item) {
return DropdownMenuItem(child: Text(item.title));
}).toList(),
onChanged: (value){},
)
);
}
},
),
class UserApi{
Future<List<User>>getUsers() async {
var data = await http.get("https://jsonplaceholder.typicode.com/albums/");
var jsonData = json.decode(data.body);
List<User> users = [];
for(var u in jsonData){
User user = User(u["id"], u["title"]);
users.add(user);
}
return users;
}
class User {
final int id;
final String title;
User(this.id,this.title);
}

Answer 1

Ok I just read the comment left above if your problem is getting your data then this might not help you but if snapshot has data this will work
//initialize this outside your build method
String dropDownValue;
FutureBuilder(
future:userApi.getUsers(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
return snapshot.hasData
? Container(
child: DropdownButton<String>(
hint: Text(dropDownValue ?? 'Make a selection'),
items: snapshot.data.map<DropdownMenuItem<String>>((item) {
return DropdownMenuItem<String>(
value: item.title,
child: Text(item.title),
);
}).toList(),
onChanged: (value) {
setState(() {
dropDownValue = value;
print(value);
});
},
),
)
: Container(
child: Center(
child: Text('Loading...'),
),
);
},
),

Answer 2

you can call the map function on any list converting the elements of the list.
return DropdownButton(
items: snapshot.data.map((item) {
return DropdownMenuItem(child: Text(item.title));
}).toList(),
onChanged: (value){},
);
if you can see here we're converting the list snapshot.data to another list of DropdownMenuItem type by calling map on snapshot.data the map function takes another function that's being called on every element of snapshot.data , map returns an Iterable of type DropdownMenuItem (the returned type of the function being called on every element) and we convert the Iterable to a list by calling toList() on it
I wish that is explanatory enough, the map function is very useful.