MaskTextInputFormatter erases characters when I do the insertion about mask_text_input_formatter HOT 2 CLOSED

class _MyHomePageState extends State<MyHomePage> {
  final  maskFormatter = MaskTextInputFormatter( mask: '+### ###-##-##');
  @override
  Widget build(BuildContext context) {
    return Scaffold(
     body: Padding(
       padding: const EdgeInsets.all(8.0),
       child: Column(
        children: [
          SizedBox(height: 50,),
          TextField(
            keyboardType: TextInputType.number,
            decoration: InputDecoration(
              hintText: 'Enter Phone Number'
              ),
              inputFormatters: [
                maskFormatter
              ],
          ),
        ],
       ),
     ), 
    );
  }
}