我正在使用颤振文本字段(不是文本表单字段)制作温度转换器应用程序我需要限制多个点和多个符号(+-)？

Question

我需要限制有多个符号，并且我只需要有+、-、.和数字(Flutter文本字段(

Answer 1

class MyHomePage extends StatefulWidget {
@override
MyHomePageState createState() {
return new MyHomePageState();
}
}
class MyHomePageState extends State<MyHomePage> {
final _text = TextEditingController();
bool _validate = false;
@override
void dispose() {
_text.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('TextField Demo'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
TextField(
controller: _text,
decoration: InputDecoration(
labelText: 'Enter the Value',
errorText: !_validate ? 'Your Message' : null,
),
),
RaisedButton(
onPressed: () {
setState(() {
// **The Condition**
if ('.'.allMatches(_text.text).length > 1 &&
('+'.allMatches(_text.text).length > 1 ||
'-'.allMatches(_text.text).length > 1)) {
_validate = true;
} else {
_validate = false;
}
});
},
child: Text('Submit'),
textColor: Colors.white,
color: Colors.blueAccent,
)
],
),
),
);
}
}