设置键盘和验证器

String numberValidator(String value) {
  if(value == null) {
    return null;
  }
  final n = num.tryParse(value);
  if(n == null) {
    return '"$value" is not a valid number';
  }
  return null;
}

new TextFormField(
    keyboardType: TextInputType.number, 
    validator: numberValidator, 
    textAlign: TextAlign.right
    ...

https://docs.flutter.io/flutter/material/TextFormField/TextFormField.html https://docs.flutter.io/flutter/services/TextInputType-class.html

你可以试试这个:

TextFormField(
     keyboardType: TextInputType.number,
     decoration: InputDecoration(
              prefixIcon: Text("Enter your number: ")
     ),
     initialValue: "5",
     onSaved: (input) => _value = num.tryParse(input),
),

keyboardType: TextInputType。number会在焦点上打开一个num pad，当用户输入/经过任何其他内容时，我将清除文本字段。

keyboardType: TextInputType.number,
onChanged: (String newVal) {
    if(!isNumber(newVal)) {
        editingController.clear();
    }
}

// Function to validate the number
bool isNumber(String value) {
    if(value == null) {
        return true;
    }
    final n = num.tryParse(value);
    return n!= null;
}

为避免粘贴的不是数字值，添加后

keyboardType: TextInputType.number

这段代码:

inputFormatters: [FilteringTextInputFormatter.digitsOnly] 

从https://api.flutter.dev/flutter/services/FilteringTextInputFormatter-class.html

只需将此添加到您的TextFormField

  keyboardType: TextInputType.number,
  inputFormatters: <TextInputFormatter>[
  FilteringTextInputFormatter.allow(RegExp(r'[0-9]')), ],

的例子,

TextFormField(
        controller: textController,
        onChanged: (value) {
         print(value);
        },
        keyboardType: TextInputType.number,
        inputFormatters: <TextInputFormatter>[
          FilteringTextInputFormatter.allow(RegExp(r'[0-9]')),
        ],
      ),

U可以安装intl_phone_number_input包

dependencies:
  intl_phone_number_input: ^0.5.2+2

试试下面的代码:

import 'package:flutter/material.dart';
import 'package:intl_phone_number_input/intl_phone_number_input.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var darkTheme = ThemeData.dark().copyWith(primaryColor: Colors.blue);

    return MaterialApp(
      title: 'Demo',
      themeMode: ThemeMode.dark,
      darkTheme: darkTheme,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(title: Text('Demo')),
        body: MyHomePage(),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final GlobalKey<FormState> formKey = GlobalKey<FormState>();

  final TextEditingController controller = TextEditingController();
  String initialCountry = 'NG';
  PhoneNumber number = PhoneNumber(isoCode: 'NG');

  @override
  Widget build(BuildContext context) {
    return Form(
      key: formKey,
      child: Container(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            InternationalPhoneNumberInput(
              onInputChanged: (PhoneNumber number) {
                print(number.phoneNumber);
              },
              onInputValidated: (bool value) {
                print(value);
              },
              selectorConfig: SelectorConfig(
                selectorType: PhoneInputSelectorType.BOTTOM_SHEET,
                backgroundColor: Colors.black,
              ),
              ignoreBlank: false,
              autoValidateMode: AutovalidateMode.disabled,
              selectorTextStyle: TextStyle(color: Colors.black),
              initialValue: number,
              textFieldController: controller,
              inputBorder: OutlineInputBorder(),
            ),
            RaisedButton(
              onPressed: () {
                formKey.currentState.validate();
              },
              child: Text('Validate'),
            ),
            RaisedButton(
              onPressed: () {
                getPhoneNumber('+15417543010');
              },
              child: Text('Update'),
            ),
          ],
        ),
      ),
    );
  }

  void getPhoneNumber(String phoneNumber) async {
    PhoneNumber number =
        await PhoneNumber.getRegionInfoFromPhoneNumber(phoneNumber, 'US');

    setState(() {
      this.number = number;
    });
  }

  @override
  void dispose() {
    controller?.dispose();
    super.dispose();
  }
}