如何在fluttter中添加整数作为TextFormField的默认值/初始值？

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = TextEditingController(text: '10');
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      controller: _controller,
      keyboardType: TextInputType.number,
      decoration: InputDecoration(
        labelText: '整数值',
      ),
    );
  }
}