home_page.dart

gistfile1.dart

import 'package:flutter/material.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  
  //regra de negócio
  double _value = 0.0;

  _onChangeValue(double v) {
    setState(() {
      _value = v;
    });
  }

  //fim da regra de negócio

  Widget _textValue() {
    return Text(
      "Value: ${_value.toStringAsPrecision(1)}",
      style: TextStyle(
        color: Colors.white,
        fontSize: 24,
        fontWeight: FontWeight.bold,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    print("reconstruindo");

    return Material(
      color: Color.lerp(Colors.red, Colors.purple, 0.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          _textValue(),
          Container(
            height: 25,
          ),
          Slider(
              activeColor: Colors.white,
              inactiveColor: Colors.white,
              min: 0.0,
              max: 1.0,
              onChanged: _onChangeValue,
              value: _value),
        ],
      ),
    );
  }
}