How to use sort function in list view flutter

Just check out this example I have created from your given sample code :

import 'package:flutter/material.dart';
import 'package:percent_indicator/linear_percent_indicator.dart';

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

class MyApp extends StatefulWidget {
  MyApp({Key key}) : super(key: key);

  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: SafeArea(child: SampleApp()),
      ),
    );
  }
}

class SampleApp extends StatefulWidget {
  SampleApp({Key key}) : super(key: key);

  @override
  _SampleAppState createState() => _SampleAppState();
}

class _SampleAppState extends State<SampleApp> {
  var products = [
    Product("sample", 12),
    Product("name", 50),
    Product("azpc", 78),
    Product("hplm", 3),
    Product('ampl', 2),
  ];

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    products.sort((a, b) => a.price.compareTo(b.price));
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: ListView.separated(
          itemBuilder: (context, index) {
            return Card(
              child: Padding(
                padding: const EdgeInsets.all(8.0),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(products[index].name),
                    Text(products[index].price.toString()),
                  ],
                ),
              ),
            );
          },
          separatorBuilder: (context, int) => Divider(),
          itemCount: products.length),
    );
  }
}

class Product {
  final String name;
  final double price;

  Product(this.name, this.price);
}

Let me know if it works.