Flutter DropDownbutton not showing selected values - flutter

Question

The dropdown doesn't show it as the chosen one, it just continues as though nothing was selected. Please help me to solve the problem.
I created this custom dropdown widget for multiple usages...
class _AddItemWidgetState extends State<AddItemWidget> {
static const categoryTypes = [
"SL",
"KA",
];
static const subCategoryType = [
"10KG",
"20KG",
"5KG",
];
static const Type = [
"Big Tray",
"Small Tray",
];
String categorySelectedValue;
String subCategorySelectedValue;
String itemType;
Widget categoryFieldWidget(
{String name, List<String> nameList, String selectedValue}) {
return Container(
height: 49,
child: FormField<String>(
builder: (FormFieldState<String> state) {
return InputDecorator(
decoration: InputDecoration(
contentPadding: EdgeInsets.only(left: 10, right: 10),
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(5.0))),
child: DropdownButtonHideUnderline(
child: DropdownButton<String>(
icon: Icon(Icons.keyboard_arrow_down),
hint: Text(
name,
),
onChanged: (String newValue) {
setState(() {
selectedValue = newValue;
});
print(selectedValue);
},
value: selectedValue,
isDense: true,
items: nameList.map((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
),
),
);
},
),
);
}
Usage:-
But when I use this custom dropdown widget in other widgets, the value is not showing on the Ui.
"categorySelectedValue"'s value changes...but it's not showing on the Ui...
Expanded(
child: categoryFieldWidget(
name: "Category",
nameList: categoryTypes,
selectedValue: categorySelectedValue)),

Answer 1

Just check out this example
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Users'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
static const categoryTypes = [
"SL",
"KA",
];
static const subCategoryType = [
"10KG",
"20KG",
"5KG",
];
static const itemtype = [
"Big Tray",
"Small Tray",
];
String categorySelectedValue;
String subCategorySelectedValue;
String itemType;
#override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
child: Column(
children: <Widget>[
Container(
height: 100,
child: CustomDropDown(
callback: (value) {
print('This is the category callbackValue : $value');
},
name: 'Category',
list: categoryTypes,
selectedValue: categorySelectedValue,
),
),
Container(
height: 100,
child: CustomDropDown(
callback: (value) {
print('This is the subcategory callbackValue : $value');
},
name: 'SubCategory',
list: subCategoryType,
selectedValue: subCategorySelectedValue,
),
),
Container(
height: 100,
child: CustomDropDown(
callback: (value) {
print('This is the type callbackValue : $value');
},
name: 'Type',
list: itemtype,
selectedValue: itemType,
),
),
],
),
),
);
}
}
typedef void StringCallback(String val);
class CustomDropDown extends StatefulWidget {
final StringCallback callback;
final List<String> list;
final String name;
final String selectedValue;
const CustomDropDown(
{Key key, this.list, this.name, this.selectedValue, this.callback})
: super(key: key);
#override
_CustomDropDownState createState() => _CustomDropDownState();
}
class _CustomDropDownState extends State<CustomDropDown> {
List<String> currentList = List();
String name;
String currentSelectedValue;
#override
void initState() {
super.initState();
currentList = widget.list;
name = widget.name;
currentSelectedValue = widget.selectedValue;
}
#override
Widget build(BuildContext context) {
return Container(
height: 49,
child: FormField<String>(
builder: (FormFieldState<String> state) {
return InputDecorator(
decoration: InputDecoration(
contentPadding: EdgeInsets.only(left: 10, right: 10),
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(5.0))),
child: DropdownButtonHideUnderline(
child: DropdownButton<String>(
icon: Icon(Icons.keyboard_arrow_down),
hint: Text(
widget.name,
),
onChanged: (String newValue) {
print('This is the value on select $newValue');
setState(() {
currentSelectedValue = newValue;
});
widget.callback(currentSelectedValue);
},
value: currentSelectedValue,
isDense: true,
items: currentList.map((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
),
),
);
},
),
);
}
}
Let me know if it works.