在flutter中的TextFormField中，用户输入url或网站链接以将其保存到firebase数据库，并应使用浏览器打开该链接

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

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyFormPage extends StatefulWidget {
  @override
  _MyFormPageState createState() => _MyFormPageState();
}

class _MyFormPageState extends State<MyFormPage> {
  final _formKey = GlobalKey<FormState>();
  TextEditingController _urlController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('URL保存与打开'),
      ),
      body: Form(
        key: _formKey,
        child: Column(
          children: [
            TextFormField(
              controller: _urlController,
              decoration: InputDecoration(
                labelText: 'URL',
              ),
              validator: (value) {
                if (value.isEmpty) {
                  return '请输入URL';
                }
                return null;
              },
            ),
            RaisedButton(
              onPressed: () {
                if (_formKey.currentState.validate()) {
                  saveUrlToFirebase(_urlController.text);
                }
              },
              child: Text('保存到Firebase'),
            ),
          ],
        ),
      ),
    );
  }

  void saveUrlToFirebase(String url) {
    FirebaseFirestore.instance.collection('urls').add({
      'url': url,
    }).then((value) {
      launchUrl(url);
    }).catchError((error) {
      print('保存到Firebase时出错：$error');
    });
  }

  void launchUrl(String url) async {
    if (await canLaunch(url)) {
      await launch(url);
    } else {
      print('无法打开链接：$url');
    }
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'URL保存与打开',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyFormPage(),
    );
  }
}