Flutter Autogrowth TextField

autogrowth_textfield.dart

class _MyScreenState extends State<MyScreen> {
  double _inputHeight = 50;
  final TextEditingController _textEditingController = TextEditingController();

  @override
  void initState() {
    super.initState();
    _textEditingController.addListener(_checkInputHeight);
  }

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

  void _checkInputHeight() async {
    int count = _textEditingController.text.split('\n').length;

    if (count == 0 && _inputHeight == 50.0) {
      return;
    }
    if (count <= 5) {  // use a maximum height of 6 rows 
    // height values can be adapted based on the font size
      var newHeight = count == 0 ? 50.0 : 28.0 + (count * 18.0);
      setState(() {
        _inputHeight = newHeight;
      });
    }
  }


  // ... build method here
  TextField(
    controller: _textEditingController,
    textInputAction: TextInputAction.newline,
    keyboardType: TextInputType.multiline,
    maxLines: null,
  )