anchor.diff:    TextEditingController weightController = TextEditingController();
     TextEditingController heightController = TextEditingController();
   
  +  GlobalKey<FormState> _formKey = GlobalKey<FormState>();
  +
     String _infoText = "Informe seus dados!";
   
     void _resetFields(){
       weightController.text = "";
       heightController.text = "";
  -    _infoText = "Informe seus dados!";
  +    setState(() {
  +      _infoText = "Informe seus dados!";
  +      _formKey = GlobalKey<FormState>();
  +    });
     }
   
  -
  -  void calculate(){
  +  void _calculate(){
       setState(() {
         double weight = double.parse(weightController.text);
         double height = double.parse(heightController.text) / 100;
  
positive.code:             onPressed: _resetFields,
            )
          ],
        ), //AppBar
        backgroundColor: Colors.white,
        body: SingleChildScrollView(
          padding: EdgeInsets.fromLTRB(10.0, 0.0, 10.0, 0.0),
          child:  Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            // Ocupa toda a largura da coluna
            children: <Widget>[
              Icon(Icons.person_outline, size: 120.0, color: Colors.green),
              TextField(
                keyboardType: TextInputType.number,
                decoration: InputDecoration(
                    labelText: "Peso (kg)",
                    labelStyle: TextStyle(color: Colors.green)), // InputDecoration
                textAlign: TextAlign.center,
                style: TextStyle(color: Colors.green, fontSize: 25.0),
                controller: weightController,
              ), // TextField
              TextField(
                keyboardType: TextInputType.number,
                decoration: InputDecoration(
                    labelText: "Altura (cm)",
                    labelStyle: TextStyle(color: Colors.green)), // InputDecoration
                textAlign: TextAlign.center,
                style: TextStyle(color: Colors.green, fontSize: 25.0),
                controller: heightController,
              ), // TextField
              Padding(
                padding: EdgeInsets.only(top: 10.0, bottom: 10.0),
                child: Container(
                  height: 50.0,
                  child: RaisedButton(
                    onPressed: calculate,
                    child: Text("Calcular", style: TextStyle(color: Colors.white, fontSize: 25.0),),
                    color: Colors.green,
                  ), //RaisedButton,
                ),//Container,
              ),
              Text( _infoText ,
                textAlign: TextAlign.center,
                style: TextStyle(color: Colors.green, fontSize: 25.0),
              ) // Text
            ],
          ),
        )
      ); // Scaffold
    }
  }
  
negative.code:     });
    }
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
  