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),
),

你可以指定数字为keyboardType的TextField使用:

keyboardType: TextInputType.number

检查一下我的总管。飞镖文件

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new MaterialApp(
      home: new HomePage(),
      theme: new ThemeData(primarySwatch: Colors.blue),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new HomePageState();
  }
}

class HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      backgroundColor: Colors.white,
      body: new Container(
          padding: const EdgeInsets.all(40.0),
          child: new Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          new TextField(
            decoration: new InputDecoration(labelText: "Enter your number"),
            keyboardType: TextInputType.number,
            inputFormatters: <TextInputFormatter>[
    FilteringTextInputFormatter.digitsOnly
], // Only numbers can be entered
          ),
        ],
      )),
    );
  }
}

如果需要使用双位数:

keyboardType: TextInputType.numberWithOptions(decimal: true),
inputFormatters: [FilteringTextInputFormatter.allow(RegExp('[0-9.,]')),],
onChanged: (value) => doubleVar = double.parse(value),

RegExp('[0-9.，]')允许0到9之间的数字，也允许逗号和点。

double.parse()将字符串转换为double。

别忘了你需要: 导入的包:颤振/ services.dart ';

设置你的keyboardType为TextInputType.number，

例如:keyboardType: TextInputType.number，

         TextFormField(
            controller: yourcontroller,
            keyboardType: TextInputType.number,
            decoration: const InputDecoration(
              labelText: 'Mobile',
              suffixIcon: Padding(
                padding: EdgeInsets.only(),
                child:
                Icon(Icons.phone_outlined, color: Color(0xffff4876)),
              ),
            ),
            validator: (text) {
              if (text == null || text.isEmpty) {
                return 'Please enter your Mobile No.';
              }
              return null;
            },
          ),

这里是关于如何添加数字键盘，如何进行验证，如何添加样式，以及dart/flutter中的其他内容的所有细节。 我希望它能帮助你更好地学习。

Padding(
            padding: const EdgeInsets.all(3.0),
            child: TextFormField(
              maxLength: 10,
              keyboardType: TextInputType.number,
              validator: (value) {
                if (value.isEmpty) {
                  return 'Enter Number Please';
                }
                
                return null;
              },
              decoration: InputDecoration(
                prefixIcon: Icon(Icons.smartphone),
                prefixText: '+92',
                labelText: 'Enter Phone Number',
                contentPadding: EdgeInsets.zero,
                enabledBorder: OutlineInputBorder(),
                focusedBorder: OutlineInputBorder(
                    borderSide: BorderSide(
                      width: 2, color: Theme
                        .of(context)
                        .primaryColor,
                    )
                ),
                focusColor: Theme
                    .of(context)
                    .primaryColor,
              ),
            ),
          ),

对于数字输入或数字键盘，您可以使用keyboardType: TextInputType.number

TextFormField(
  decoration: InputDecoration(labelText:'Amount'),
    controller: TextEditingController(
  ),
  validator: (value) {
    if (value.isEmpty) {
      return 'Enter Amount';
    }
  },
  keyboardType: TextInputType.number
)