dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2
  url_launcher: ^5.0.1

在VS Code中，儲存後就會自動下載（但並不在專案中，而是在flutter的安裝目錄下，例如：C:\tools\flutter\.pub-cache\hosted\pub.dartlang.org）

安裝使用從installing就有詳細說明，如：https://pub.dartlang.org/packages/url_launcher#-installing-tab-

完整範例：

import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: '使用工具包',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('url_launcher 工具包'),
        ),
        body: new Center(
          child: new RaisedButton(
            onPressed: (){
              const url='https://schoolweb.tn.edu.tw';
              launch(url);
            },
            child: new Text('打開集中式校網'),
          ),
        ),
      ),
    );
  }
}