anchor.diff:              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
  -          ],
  +        child: Form(
  +          key: _formKey,
  +          child: Column(
  +            crossAxisAlignment: CrossAxisAlignment.stretch,
  +            children: <Widget>[
  +              Icon(Icons.person_outline, size: 120.0, color: Colors.green),
  +              TextFormField(
  +                keyboardType: TextInputType.number,
  +                decoration: InputDecoration(
  +                    labelText: "Peso (kg)",
  +                    labelStyle: TextStyle(color: Colors.green)),
  +                textAlign: TextAlign.center,
  +                style: TextStyle(color: Colors.green, fontSize: 25.0),
  +                controller: weightController,
  +                validator: (value) {
  +                  if(value.isEmpty){
  +                    return "Insira seu Peso!";
  +                  }
  +                },
  +              ),
  +              TextFormField(
  +                keyboardType: TextInputType.number,
  +                decoration: InputDecoration(
  +                    labelText: "Altura (cm)",
  +                    labelStyle: TextStyle(color: Colors.green)),
  +                textAlign: TextAlign.center,
  +                style: TextStyle(color: Colors.green, fontSize: 25.0),
  +                controller: heightController,
  +                validator: (value) {
  +                  if(value.isEmpty){
  +                    return "Insira sua Altura!";
  +                  }
  +                },
  +              ),
  +              Padding(
  +                padding: EdgeInsets.only(top: 10.0, bottom: 10.0),
  +                child: Container(
  +                  height: 50.0,
  +                  child: RaisedButton(
  +                    onPressed: () {
  +                      if(_formKey.currentState.validate()){
  +                        _calculate();
  +                      }
  +                    },
  +                    child: Text(
  +                      "Calcular",
  +                      style: TextStyle(color: Colors.white, fontSize: 25.0),
  +                    ),
  +                    color: Colors.green,
  +                  ),
  +                ),
  +              ),
  +              Text(
  +                _infoText,
  +                textAlign: TextAlign.center,
  +                style: TextStyle(color: Colors.green, fontSize: 25.0),
  +              )
  +            ],
  +          ),
           ),
  -      )
  -    ); // Scaffold
  +      ),
  +    );
     }
   }
  
positive.code:   TextEditingController weightController = TextEditingController();
    TextEditingController heightController = TextEditingController();
  
    String _infoText = "Informe seus dados!";
  
    void _resetFields(){
      weightController.text = "";
      heightController.text = "";
      _infoText = "Informe seus dados!";
    }
  
  
    void calculate(){
      setState(() {
        double weight = double.parse(weightController.text);
        double height = double.parse(heightController.text) / 100;
  
negative.code:     });
    }
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
  