试试这个：

TextField(
                      decoration: InputDecoration(
                        labelText: 'Enter a number:',
                      ),
                      keyboardType:
                          TextInputType.numberWithOptions(decimal: true),
                      inputFormatters: [
                        FilteringTextInputFormatter(
                            RegExp(r'^\d*\.?\d{0,1}$'),
                            allow: true),
                      ],
                    ),

解决了。

List<TextInputFormatter>? inputFormatters = [
  FilteringTextInputFormatter.allow(
    RegExp(r'(^\d*\.?\d*)'),
  ),

  FilteringTextInputFormatter.deny(
    RegExp(r'\.\.+'), 
    replacementString: '.',
  ),

  FilteringTextInputFormatter.deny(
    RegExp(r'^\.'), 
    replacementString: '0.',
  ),

  FilteringTextInputFormatter.deny(
    RegExp(r'\d+-'), 
  ),

  FilteringTextInputFormatter.deny(
    RegExp(r'\.-'),
    replacementString: '.',
  ),

  FilteringTextInputFormatter.deny(
    RegExp(r'-\.+'),
  ),

  FilteringTextInputFormatter.deny(
    RegExp(r'^0\d+'),
    replacementString: '0.',
  ),
];