我在Android Studio中使用Flutter的Dart从Firestore提取数据时遇到问题。尝试执行与null相同的数据搜索时，因为我是新手，因此希望使用该语言从堆栈厨房中获取帮助
我尝试更改软件包的版本，但到目前为止没有任何改变：
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): java.lang.IllegalStateException: FirebaseApp with name [DEFAULT] doesn't exist.
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@16.0.2:274)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin.getFirestore(CloudFirestorePlugin.java:82)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin.getCollectionReference(CloudFirestorePlugin.java:87)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin.getQuery(CloudFirestorePlugin.java:139)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin.onMethodCall(CloudFirestorePlugin.java:491)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:201)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.view.FlutterNativeView$PlatformMessageHandlerImpl.handleMessageFromDart(FlutterNativeView.java:188)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:202)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at android.os.MessageQueue.next(MessageQueue.java:325)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at android.os.Looper.loop(Looper.java:142)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at android.app.ActivityThread.main(ActivityThread.java:6592)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
E/MethodChannel#plugins.flutter.io/cloud_firestore(31512): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:769)
I/flutter (31512): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (31512): The following NoSuchMethodError was thrown building FutureBuilder<dynamic>(dirty, state:
I/flutter (31512): _FutureBuilderState<dynamic>#7e966):
I/flutter (31512): The getter 'length' was called on null.
I/flutter (31512): Receiver: null
I/flutter (31512): Tried calling: length
I/flutter (31512):
I/flutter (31512): When the exception was thrown, this was the stack:
I/flutter (31512): #0 Object.noSuchMethod (dart:core/runtime/libobject_patch.dart:50:5)
I/flutter (31512): #1 _ListPageState.build.<anonymous closure> (package:central/main.dart:74:40)
I/flutter (31512): #2 _FutureBuilderState.build (package:flutter/src/widgets/async.dart)
I/flutter (31512): #3 StatefulElement.build (package:flutter/src/widgets/framework.dart:3825:27)
I/flutter (31512): #4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3736:15)
I/flutter (31512): #5 Element.rebuild (package:flutter/src/widgets/framework.dart:3559:5)
I/flutter (31512): #6 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2273:33)
I/flutter (31512): #7 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:700:20)
I/flutter (31512): #8 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:268:5)
I/flutter (31512): #9 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:988:15)
I/flutter (31512): #10 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:928:9)
I/flutter (31512): #11 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:749:7)
I/flutter (31512): #20 _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
I/flutter (31512): #21 _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
I/flutter (31512): #22 _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:171:12)
I/flutter (31512): (elided 8 frames from package dart:async)
我正在尝试返回数据列表，但是它给出了错误，好像在Firestore中没有了