你可以添加键盘类型的输入格式，就像这样

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

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;
}

以下是Flutter中实际手机键盘的代码:

     //Mobile
            const TextField(
              keyboardType: TextInputType.number,
              decoration: InputDecoration(
                  prefixIcon: Icon(Icons.phone), hintText: 'Mobile'),
            ),

对于那些正在寻找使TextField或TextFormField只接受数字作为输入的人，尝试以下代码块:

用于flutter 1.20或更新版本

TextFormField(
  controller: _controller,
  keyboardType: TextInputType.number,
  inputFormatters: <TextInputFormatter>[
   // for below version 2 use this
 FilteringTextInputFormatter.allow(RegExp(r'[0-9]')), 
// for version 2 and greater youcan also use this
 FilteringTextInputFormatter.digitsOnly

  ],
  decoration: InputDecoration(
    labelText: "whatever you want",
    hintText: "whatever you want",
    icon: Icon(Icons.phone_iphone)
  )
)

对于1.20的早期版本

TextFormField(
    controller: _controller,
    keyboardType: TextInputType.number,
    inputFormatters: <TextInputFormatter>[
        WhitelistingTextInputFormatter.digitsOnly
    ],
    decoration: InputDecoration(
        labelText:"whatever you want", 
        hintText: "whatever you want",
        icon: Icon(Icons.phone_iphone)
    )
)

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

TextField(
  controller: _controller,
  keyboardType: TextInputType.number,
  inputFormatters: <TextInputFormatter>[
  FilteringTextInputFormatter.allow(RegExp(r'[0.0-9.9]')),
 ])