Input box assembly of the shutter package

class LoginInput extends StatefulWidget {
    
  final String title;
  final String hint;
  final ValueChanged<String> onChanged; //  Input the callback in the input box 
  final ValueChanged<bool> focusChanged; //  Get focus callback 
  final bool lineStretch; //  Whether extensibility is supported 
  final bool obscureText; //
  final TextInputType keyboardType; //  Input type 

  LoginInput(this.title, this.hint,
      {
    Key key,
      this.onChanged,
      this.focusChanged,
      this.lineStretch,
      this.obscureText,
      this.keyboardType})
      : super(key: key);

  @override
  _LoginInputState createState() => _LoginInputState();
}

class _LoginInputState extends State<LoginInput> {
    
  final _focusNode = FocusNode();

  @override
  void initState() {
    
    super.initState();
    //  Whether to get cursor monitoring 
    _focusNode.addListener(() {
    
      print("Has focus: ${_focusNode.hasFocus}");
      //  Callback the input box to get focus 
      widget.focusChanged(_focusNode.hasFocus);
    });
  }

  @override
  void dispose() {
    
    super.dispose();
    //  Cancel getting focus 
    _focusNode.dispose();
  }

  @override
  Widget build(BuildContext context) {
    
    return Column(
      children: [
        Row(
          children: [
            Container(
              padding: EdgeInsets.only(left: 15),
              width: 100,
              child: Text(
                widget.title,
                style: TextStyle(fontSize: 16),
              ),
            ),
            _input(),
          ],
        ),
        Padding(
          padding: EdgeInsets.only(left: !widget.lineStretch ? 15 : 0),
          child: Divider(
            //  line 
            height: 1,
            thickness: 0.5, //  The thickness of the thread 
          ),
        ),
      ],
    );
  }

  _input() {
    
    return Expanded(
        child: TextField(
      focusNode: _focusNode,
      onChanged: widget.onChanged,
      //  Input box content change callback 
      obscureText: widget.obscureText,
      //  Whether to hide the input text , Common words input password 
      keyboardType: widget.keyboardType,
      //  Input type 
      autofocus: !widget.obscureText,
      //  Get focus automatically 
      cursorColor: primary,
      //  Cursor color 
      style: TextStyle(
          fontSize: 16, color: Colors.black, fontWeight: FontWeight.w300),
      decoration: InputDecoration(
          //  Input text decoration 
          contentPadding: EdgeInsets.only(left: 20, right: 20), //  padding 
          border: InputBorder.none, //  Do not display the input box border 
          hintText: widget.hint ?? '',
          hintStyle: TextStyle(fontSize: 15, color: Colors.grey)),
    ));
  }
}