正如接受的答案所述，指定keyboardType会触发一个数字键盘:

keyboardType: TextInputType.number

其他好的回答指出，一个简单的基于正则表达式的格式化器可以用来只允许输入整数:

inputFormatters: [
  FilteringTextInputFormatter.allow(RegExp(r'[0-9]')),
],

这样做的问题是正则表达式一次只匹配一个符号，因此限制小数点的数量(例如)不能通过这种方式实现。

另外，其他人也表明，如果一个人想验证一个十进制数，它可以通过使用TextFormField和它的验证器参数来实现:

new TextFormField(
    keyboardType: TextInputType.number, 
    validator: (v) => num.tryParse(v) == null ? "invalid number" : null, 
    ...

这样做的问题是，它不能交互式地实现，而只能在表单提交时实现。

我希望只允许输入十进制数字，而不是稍后验证。我的解决方案是编写一个自定义格式化器利用int.tryParse:

/// Allows only decimal numbers to be input.
class DecimalNumberFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue, TextEditingValue newValue) {
    // Allow empty input and delegate formatting decision to `num.tryParse`.
    return newValue.text != '' && num.tryParse(newValue.text) == null
        ? oldValue
        : newValue;
  }
}

另外，也可以为自定义格式化器使用regex，这将应用于整个输入，而不仅仅是单个符号:

/// Allows only decimal numbers to be input. Limits decimal plates to 3.
class DecimalNumberFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue, TextEditingValue newValue) {
    // Allow empty input.
    if (newValue.text == '') return newValue;

    // Regex: can start with zero or more digits, maybe followed by a decimal
    // point, followed by zero, one, two, or three digits.
    return RegExp('^\\d*\\.?\\d?\\d?\\d?\$').hasMatch(newValue.text)
        ? newValue
        : oldValue;
  }
}

这样，我还可以将小数板的数量限制为3。

您可以将这两个属性与TextFormField一起使用

 TextFormField(
         keyboardType: TextInputType.number
         inputFormatters: [WhitelistingTextInputFormatter.digitsOnly],

它只允许输入数字，没有其他的东西。

https://api.flutter.dev/flutter/services/TextInputFormatter-class.html

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();
  }
}

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),
),

对于那些需要在文本字段中使用货币格式的人:

只使用:，(逗号)和。(期)

并阻止符号:-(连字符，减号或破折号)

以及:⌴(空格)

在你的TextField，只需设置以下代码:

keyboardType: TextInputType.numberWithOptions(decimal: true),
inputFormatters: [BlacklistingTextInputFormatter(new RegExp('[\\-|\\ ]'))],

符号连字符和空格仍然会出现在键盘上，但会被阻塞。

TextField小部件需要设置keyboardType: 和inputFormatters: <TextInputFormatter>[FilteringTextInputFormatter。digitsOnly]只接受数字作为输入。

     TextField(
            keyboardType: TextInputType.number,
            inputFormatters: <TextInputFormatter>[
              FilteringTextInputFormatter.digitsOnly
            ], // Only numbers can be entered
          ),

在DartPad中的例子

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

    void main() => runApp(new MyApp());
    
    class MyApp extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          home: HomePage(),
          theme: ThemeData(primarySwatch: Colors.blue),
        );
      }
    }
    
    class HomePage extends StatefulWidget {
      @override
      State<StatefulWidget> createState() {
        return HomePageState();
      }
    }
    
    class HomePageState extends State<HomePage> {
      @override
      Widget build(BuildContext context) {
        return Scaffold(
          backgroundColor: Colors.white,
          body: Container(
              padding: const EdgeInsets.all(40.0),
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  Text("This Input accepts Numbers only"),
                  SizedBox(height: 20),
                  TextField(
                    decoration: InputDecoration(
                      focusedBorder: OutlineInputBorder(
                        borderSide:
                            BorderSide(color: Colors.greenAccent, width: 5.0),
                      ),
                      enabledBorder: OutlineInputBorder(
                        borderSide: BorderSide(color: Colors.red, width: 5.0),
                      ),
                      hintText: 'Mobile Number',
                    ),
                    keyboardType: TextInputType.number,
                    inputFormatters: <TextInputFormatter>[
                      FilteringTextInputFormatter.digitsOnly
                    ], // Only numbers can be entered
                  ),
                  SizedBox(height: 20),
                  Text("You can test be Typing"),
                ],
              )),
        );
      }
    }