名称为DEFAULT的Flatter Firebase实时数据库FirebaseApp不'；不存在。可用应用程序名称：[默认值]

我是如何进行回购的：

• flatter create--androidx-i swift-a kotlin测试\u firebase\u应用程序

• 遵循Flatter Firebase的说明
• 在

  android/build.gradle中将kotlin版本升级到
  1.3.50

• 将gradle版本升级到3.5.0

• 升级gradle包装器distributionUrl

• 在android/app/build.gradle中添加android x支持库

• 在android/app/build.gradle的末尾应用google服务插件

• 在

  main.dart

void main（）{
final firebaseApp=firebaseApp（名称：“默认”）；
final db=FirebaseDatabase(
应用程序：firebaseApp
).reference（）；
打印（'检查数据库连接！'）；
db.child（'rooms'）.once（）。然后（（result）=>print（'result=$result'）；
runApp（MyApp（））；
}

获取错误：

[        ] I/flutter (20246): checking db connection!
[  +38 ms] E/MethodChannel#plugins.flutter.io/firebase_database(20246): Failed to handle method call
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246): java.lang.IllegalStateException: FirebaseApp with name DEFAULT doesn't exist. Available app names: [DEFAULT]
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@17.0.0:269)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.plugins.firebase.database.FirebaseDatabasePlugin.onMethodCall(FirebaseDatabasePlugin.java:241)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:222)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:96)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:656)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.os.MessageQueue.nativePollOnce(Native Method)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.os.MessageQueue.next(MessageQueue.java:326)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.os.Looper.loop(Looper.java:160)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.app.ActivityThread.main(ActivityThread.java:6669)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at java.lang.reflect.Method.invoke(Native Method)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

---

我终于找到了解决办法

改变这个

final firebaseApp=firebaseApp（名称：“默认”）；

对此

final firebaseApp=firebaseApp（名称：“[默认]”）；

    dependencies {
       classpath 'com.android.tools.build:gradle:3.5.0'
    }

    distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-all.zip

    dependencies {
        // ...
        implementation 'androidx.appcompat:appcompat:1.1.0'
        implementation "androidx.core:core-ktx:1.1.0"
    }

    apply plugin: 'com.google.gms.google-services'

[        ] I/flutter (20246): checking db connection!
[  +38 ms] E/MethodChannel#plugins.flutter.io/firebase_database(20246): Failed to handle method call
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246): java.lang.IllegalStateException: FirebaseApp with name DEFAULT doesn't exist. Available app names: [DEFAULT]
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@17.0.0:269)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.plugins.firebase.database.FirebaseDatabasePlugin.onMethodCall(FirebaseDatabasePlugin.java:241)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:222)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:96)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:656)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.os.MessageQueue.nativePollOnce(Native Method)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.os.MessageQueue.next(MessageQueue.java:326)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.os.Looper.loop(Looper.java:160)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at android.app.ActivityThread.main(ActivityThread.java:6669)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at java.lang.reflect.Method.invoke(Native Method)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
[        ] E/MethodChannel#plugins.flutter.io/firebase_database(20246):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)