我有一个Text()
小部件和一个带有TextFormField()
的TextInputType.number
小部件。我想要的是用户在TextFormField()
中键入减法运算应该实时进行。
[在TextFormField()
中输入的值应在用户在Text()
中键入数字时自动减去TextFormField()
小部件中的值;
[Note最终的结果应该显示在相同的Text()
小部件中,因为所有这些键入和减法都在进行。
import 'package:flutter/material.dart';
class ChangeValuesPage extends StatefulWidget {
@override
_ChangeValuesPageState createState() {
return _ChangeValuesPageState();
}
}
class _ChangeValuesPageState extends State<ChangeValuesPage> {
final pureNumbers = RegExp(r'^[0-9]+$');
int numberValue = 200;
int latestNumberValue;
final formKey = new GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: appbar(context, 'Simple App', 'otherData'),
drawer: TopDrawer(),
body: SingleChildScrollView(
child: new Card(
child: Padding(
padding: EdgeInsets.all(5.0),
child: new Column(
children: <Widget>[
/**
* Below is the Text() field where subtraction math should occure.
*/
/// The value in the Text() widget should be subtracted automatically with
/// the number values inside the TextFormField() widget automatically as the user is typing the numbers
Text(
'Number value text: ${this.numberValue}',
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.bold,
),
),
SizedBox(
height: 6,
),
new Form(
key: formKey,
child: new Column(
children: <Widget>[
TextFormField(
keyboardType: TextInputType.number,
decoration: new InputDecoration(
labelText: 'Reduce number value?',
hintText: 'Default number value is "0"',
),
validator: (val) {
if (val.isEmpty == true) {
return 'Fill in number values';
}
if (pureNumbers.hasMatch(val) == false) {
return 'Use alphanumeric characters only in nickname';
}
return null;
},
onSaved: (val) => this.latestNumberValue = int.parse(val),
),
],
),
),
],
),
),
),
),
);
}
}
我尝试了不同的方法来实现这一目标,但是没有任何效果。谢谢,用爱发表。
尝试为onChanged
的TextFormField
属性实现此功能。希望这是您要实现的目标。
onChanged: (val) {
if (val.isEmpty) {
setState(() => numberValue = 200);
} else {
numberValue = 200;
setState(() => numberValue -= int.parse(val));
}
},