title: flutter import firebase_core,Auth,database,... but a lot error
body: <p>Error: Can't use '/C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_core_platform_interface-4.4.0/lib/src/method_channel/method_channel_firebase.dart' as a part, because it has no 'part of' declaration.</p>
  <pre><code>import 'package:firebase_core/firebase_core.dart';
  import 'package:flutter/material.dart';
  import 'package:firebase_database/firebase_database.dart';
  
  void main()  {
    
    runApp(const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyApp(),
    ));
  }
  
  class MyApp extends StatefulWidget {
    const MyApp({ Key? key }) : super(key: key);
  
    @override
    State&lt;MyApp&gt; createState() =&gt; _MyAppState();
  }
  
  class _MyAppState extends State&lt;MyApp&gt; {
     //final  DatabaseReference database = FirebaseDatabase.instance.ref();
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(&quot;Realtime database1234&quot;),
          ),
      );
    }
  }
  
  </code></pre>
  <p><a href="https://i.stack.imgur.com/63nmF.png" rel="nofollow noreferrer">enter image description here</a></p>