flutter Slide拖动滑条

main.dart 

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'This is a Slide Example',
        home: Scaffold(
            appBar: AppBar(
              title: Text('ABC'),
            ),
            body: Column(children: [
              Padding(
                child: Text(
                  'This is a Slide Example',
                  style: TextStyle(fontSize: 20),
                ),
                padding: EdgeInsets.all(50),
              ),
              SlideExample(),
              RangeSliderExample()
            ])));
  }
}

class SlideExample extends StatefulWidget {
  @override
  _Slider1State createState() => _Slider1State();
}

class _Slider1State extends State {
  double rating = 0;
  @override
  Widget build(BuildContext context) {
    // TODO: implement build

    return Slider(
      label: "$rating",
      divisions: 10,
      value: rating,
      onChanged: (newRating) {
        setState(() => rating = newRating);
      },
    );
  }
}

class RangeSliderExample extends StatefulWidget {
  @override
  _RangeSliderExampleState createState() => _RangeSliderExampleState();
}

class _RangeSliderExampleState extends State {
  var selectedRange = RangeValues(0.2, 0.8);

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return RangeSlider(
      values: selectedRange,
      onChanged: (RangeValues newRange) {
        setState(() {
          selectedRange = newRange;
        });
      },
    );
  }
}