无法在 Isolate 中执行 Firebase 查询

Question

我正在使用 Flutter 开发一个应用程序。我想使用 Isolate 执行一些 Firebase 查询。但是每次我运行该应用程序时都会出现此错误并且没有显示任何内容。

这是我的代码

class HomePage extends StatefulWidget {
    HomePage({Key key, this.title}) : super(key: key);
    final String title;

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


class HomePageState extends State<HomePage>{
    Isolate _isolate;
    ReceivePort _receivePort;
    String _data;

  @override
  Widget build(BuildContext context){
    return WillPopScope(
    child: Scaffold(){
     child : Center(child:Text('${_data}'))
     });
  }


 //To start
  void _start() async {
  _receivePort = ReceivePort();
  _isolate = await Isolate.spawn(getData, _receivePort.sendPort);
  _receivePort.listen(_displayData, onDone: () {
     print("done!");
  });
}

 //Display data;
void _displayData(dynamic data) {
  setState(() {
    _data = data;
  });
 }

  static void getData(SendPort sendPort) async{
   var fire = Firestore.instance;
   fire.settings(persistenceEnabled: true); //I get an error here
   fire.document('MODEL/${id}')
    .snapshots()
    .listen((d) {//I get an error here
     sendPort.send(d);
    }
 }
}

 //I call the method _start in the initState
@override
 void initState() {
    _start();
   super.initState();
  }

这是我得到的错误

E/flutter (14817): [ERROR:flutter/runtime/dart_isolate.cc(808)] 未处理的异常：E/flutter (14817): 错误：找不到本机函数 'Window_sendPlatformMessage' (4 个参数) E/flutter (14817) ): #0 Window.sendPlatformMessage (dart:ui/window.dart:1133:9) E/flutter (14817): #1 _DefaultBinaryMessenger._sendPlatformMessage (package:flutter/src/services/binary_messenger.dart:85:15) E /flutter (14817): #2 _DefaultBinaryMessenger.send (package:flutter/src/services/binary_messenger.dart:129:12) E/flutter (14817): #3 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel .dart:309:51) E/flutter (14817)：E/flutter (14817)：#4 Query.snapshots。(package:cloud_firestore/src/query.dart:61:37) E/flutter (14817): #5 _runGuarded (dart:async/stream_controller.dart:805: 24) E/flutter (14817): #6 _BroadcastStreamController._subscribe (dart:async/broadcast_stream_controller.dart:213:7) E/flutter (14817): #7 _ControllerStream._createSubscription (dart:async/stream_controller.dart:818: 19) E/flutter (14817): E/flutter (14817): #4 Firestore.settings (package:cloud_firestore/src/firestore.dart:154:19) E/flutter (14817): E/flutter (14817): #5 HomePageState.getData (package:flutter_app/HelpFile/HomePage.dart:207:10) E/flutter (14817): #8 _StreamImpl.listen (dart:async/stream_impl.dart:472:9) E/flutter (14817) ): #9 HomePageState.getData (package:flutter_app/HomePage.dart:201:10) E/flutter (14817): E/flutter (14817): #10 _startIsolate。(dart:isolate-patch/isolate_patch.dart:308:17) E/flutter (14817): #11 _RawReceivePortImpl。

Answer 1

检查此链接https://firebase.google.com/docs/reference/android/com/google/firebase/FirebaseApp

任何 FirebaseApp 初始化都必须仅在应用程序的主进程中进行。不支持在主进程以外的进程中使用 Firebase，并且可能会导致与资源争用相关的问题。