我是Flutter新手，这是我的第一个应用程序。我一直在尝试创建一个带有下拉选择框的表单模态框，它应该从服务器接收数据。但现在我正在使用我创建的数组中的值，但在我选择一个项目后，它不会设置该值。我尝试添加setState()方法，但出现错误。请问有人可以帮助我吗？
以下是我的代码：
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:erg_app/ProfilePage.dart';
void main() => runApp(
MaterialApp(
debugShowCheckedModeBanner: false,
home: StockPage(),
)
);
class StockPage extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Inventory Data',
theme: ThemeData(
primarySwatch: Colors.green,
),
home: StockInventory(),
);
}
}
class StockInventory extends StatefulWidget {
StockInventory({Key key}) : super(key: key); //Find out meaning
@override
_StockInventoryState createState() => _StockInventoryState();
}
class _StockInventoryState extends State<StockInventory> {
List<Products> products;
List<Products> selectedProducts;
bool sort;
@override
void initState() {
sort = false;
selectedProducts = [];
products = Products.getProducts();
super.initState();
}
onSortColum(int columnIndex, bool ascending) {
if (columnIndex == 0) {
if (ascending) {
products.sort((a, b) => a.name.compareTo(b.name));
} else {
products.sort((a, b) => b.name.compareTo(a.name));
}
}
}
@override
Widget build(BuildContext context){
return Scaffold(
appBar: AppBar(
title: new Center(child: new Text('Daily Stock Taking', textAlign: TextAlign.center)),
automaticallyImplyLeading: false,
iconTheme: IconThemeData(color: Colors.white),
backgroundColor: Colors.green,),
body: Container(
child: ListView(
children: <Widget>[
Container(
margin: const EdgeInsets.only(right: 20, top: 20),
child: Align(
alignment: Alignment.bottomRight,
child: RaisedButton(
padding: EdgeInsets.fromLTRB(14, 10, 14, 10),
color: Colors.green,
child: Text("Take Inventory", style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold, fontSize: 14), ),
onPressed: () {
// Navigator.of(context).push(MaterialPageRoute(builder: (context) => ProfilePage()));
showSimpleCustomDialog(context);
},
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(50),
),
),
),
),
Container(
padding: EdgeInsets.only(top: 30, bottom: 30),
child: DataTable(
sortAscending: sort,
sortColumnIndex: 0,
columns: [
DataColumn(
label: Text("S/No", style: TextStyle(fontSize: 16)),
numeric: false,
),
DataColumn(
label: Text("Item", style: TextStyle(fontSize: 16)),
numeric: false,
onSort: (columnIndex, ascending) {
setState(() {
sort = !sort;
});
onSortColum(columnIndex, ascending);
}),
DataColumn(
label: Text("QtyInStock", style: TextStyle(fontSize: 16)),
numeric: false,
),
DataColumn(
label: Text("Unit", style: TextStyle(fontSize: 16)),
numeric: false,
),
],
rows: products
.map(
(product) => DataRow(
selected: selectedProducts.contains(product),
cells: [
DataCell(
Text(product.count),
onTap: () {
print('Selected ${product.count}');
},
),
DataCell(
Text(product.name),
onTap: () {
print('Selected ${product.name}');
},
),
DataCell(
Text(product.itemqty),
onTap: () {
print('Selected ${product.itemqty}');
},
),
DataCell(
Text(product.itemqty),
onTap: () {
print('Selected ${product.itemqty}');
},
),
]),
).toList(),
),
),
Container(
child: Center(
child: RaisedButton(
padding: EdgeInsets.fromLTRB(80, 10, 80, 10),
color: Colors.green,
child: Text("Post Inventory", style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold, fontSize: 14), ),
onPressed: () {
Navigator.of(context).push(MaterialPageRoute(builder: (context) => ProfilePage()));
},
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(50),
),
),
),
),
],
),
),
);
}
}
class Products {
String count;
String name;
String measuringunit;
String itemqty;
Products({this.count, this.name, this.itemqty, this.measuringunit});
static List<Products> getProducts() {
return <Products>[
Products(count:"1", name: "NPK Fertilizer", itemqty: "50", measuringunit: "bag",),
Products(count:"2", name: "Urea Fertilizer", itemqty: "560", measuringunit: "bag",),
Products(count:"3", name: "Spray", itemqty: "150", measuringunit: "bottles",),
];
}
}
void showSimpleCustomDialog(BuildContext context) {
String dropdownValue = 'SelectItem';
// TextEditingController _controller = TextEditingController(text: dropdownValue);
Dialog simpleDialog = Dialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(12.0),
),
child: Container(
height: 300.0,
width: 300.0,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: EdgeInsets.only(top:20, bottom: 20, left: 30, right: 10),
child: Row(
children: <Widget>[
Expanded(child:
Text(
'Item',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, ),
),
),
Container(width: 2,),
Container(
child:DropdownButton<String>(
value: dropdownValue,
onChanged: (String newValue) {
// This set state is trowing an error
setState((){
dropdownValue = newValue;
});
},
items: <String>['Fertilizers', 'Bags', 'Spray', 'Equipments']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: new Text(value),
);
})
.toList(),
),
),
],
)),
Padding(
padding: EdgeInsets.only(top:5, bottom: 5, left: 30, right: 10),
child: Row(
children: <Widget>[
Expanded(child:
Text(
'Quantity',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, ),
),
),
Container(width: 2,),
Expanded(child: TextField(
keyboardType: TextInputType.number,
decoration: InputDecoration(
labelText: 'Quantity',
hintText: 'Enter Cost Quantity',
border:OutlineInputBorder(borderRadius: BorderRadius.circular(5.0))
),
)),
],
)),
Padding(
padding: const EdgeInsets.only(left: 10, right: 10, top: 10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
RaisedButton(
color: Colors.blue,
onPressed: () {
Navigator.of(context).pop();
},
child: Text(
'Add',
style: TextStyle(fontSize: 18.0, color: Colors.white),
),
),
SizedBox(
width: 20,
),
RaisedButton(
color: Colors.red,
onPressed: () {
Navigator.pop(context);
// Navigator.of(context).push(MaterialPageRoute(builder: (context) => StockPage()));
},
child: Text(
'Cancel!',
style: TextStyle(fontSize: 18.0, color: Colors.white),
),
)
],
),
),
],
),
),
);
showDialog(context: context, builder: (BuildContext context) => simpleDialog);
}
// Dropdown Menu Class below