我如何将数据转储到两个以上的文本字段与一个建议?(颤振)

Question

我想用一个建议自动填充几个文本字段，例如:如果我选择华盛顿州作为我居住的州，我希望另一个字段将作为国家字段填充为U.S.

感谢您的关注!

Answer 1

您需要在onChanged中使用setState( )。在这个setState里面，你将改变另一个领域otherDropdownValue的值。下面是一个关于下拉菜单的小例子。

别忘了你需要一个StatefulWidget(而不是StateLess)

代码:

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
String dropdownValue = 'One';
String otherDropdownValue = 'Two';
@override Widget build(BuildContext context) {
return Column(children: [
DropdownButton<String>(
value: dropdownValue,
onChanged: (String? newValue) {
//******************************************
//*****Here is what you are looking for*****
//******************************************
setState(() {
dropdownValue = newValue;
otherDropdownValue = newValue; ///Changes the other one
});
},
items: <String>['One', 'Two', 'Free', 'Four'].map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(value: value, child: Text(value),);}).toList(),
),
DropdownButton<String>(
value: otherDropdownValue,
onChanged: (String? newValue) {
setState(() {
otherDropdownValue = newValue; 
});
},
items: <String>['One', 'Two', 'Free', 'Four'].map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(value: value, child: Text(value),);}).toList(),
),
],
);
}
}

如果没有帮助，请告诉我。

编辑回复你最后的评论:

同样的逻辑适用于TextField或textformfield。您需要添加一个TextEditingController()来控制显示的文本。下面是一个完整的工作示例(您需要查看的部分在末尾)

，这里是一个解释代码的链接(注意，我根据您的特定用例调整了代码)

https://flutter.dev/docs/cookbook/forms/text-field-changes

import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Retrieve Text Input',
home: MyCustomForm(),
);
}
}
// Define a custom Form widget.
class MyCustomForm extends StatefulWidget {
const MyCustomForm({Key? key}) : super(key: key);
@override
_MyCustomFormState createState() => _MyCustomFormState();
}
// Define a corresponding State class.
// This class holds data related to the Form.
class _MyCustomFormState extends State<MyCustomForm> {
// Create a text controller and use it to retrieve the current value
// of the TextField.
final myController = TextEditingController();
@override
void initState() {
super.initState();
// Start listening to changes.
myController.addListener(_printLatestValue);
}
@override
void dispose() {
// Clean up the controller when the widget is removed from the widget tree.
// This also removes the _printLatestValue listener.
myController.dispose();
super.dispose();
}
void _printLatestValue() {
print('Second text field: ${myController.text}');
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Retrieve Text Input'),
),
body: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
children: [
///********************
///**** LOOK HERE  ****
///********************
TextField(
onChanged: (text) {
myController.text = text;
},
),
TextField(
controller: myController,
),
],
),
),
);
}
}