无法获取 FirebaseDatabase 实例。在 FirebaseApp 中指定 DatabaseURL

FirebaseApp 调用时抛出异常FirebaseDatabase.getInstance().

错误信息

无法获取 FirebaseDatabase 实例：在其中指定 DatabaseURL FirebaseApp 或来自您的 getInstance() 调用。

Firebase项目配置正确。Authentication工作正常，但无法连接到firebase.

这是我的应用程序级别 gradle.build 文件

构建.gradle

dependencies {
    .....

    //Firebase database
    implementation 'com.google.firebase:firebase-database:11.6.2'
    // Firebase Invitation
    implementation 'com.google.firebase:firebase-invites:11.6.2'
    // Firebase Authentication
    implementation 'com.google.firebase:firebase-auth:11.6.2'
    // Google Sign In SDK (only required for Google Sign In)
    implementation 'com.google.android.gms:play-services-auth:11.6.2'

    // people api request libraries
    implementation 'com.google.api-client:google-api-client:1.22.0'
    implementation 'com.google.api-client:google-api-client-android:1.22.0'
    implementation 'com.google.apis:google-api-services-people:v1-rev4-1.22.0'
    compile project(':customsupport')
}

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

以及项目级别构建.gradle file

buildscript {
    repositories {
        jcenter()
        maven { url 'https://maven.fabric.io/public' }
    }

    dependencies {
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
        classpath 'com.android.tools.build:gradle:3.0.1'
        classpath 'com.google.gms:google-services:3.1.2'

        // We recommend changing it to the latest version from our changelog:
        // https://docs.fabric.io/android/changelog.html#fabric-gradle-plugin
        classpath 'io.fabric.tools:gradle:1.24.4'
    }
}

An 数据库异常将发生在FirebaseDatabase.class

public static synchronized FirebaseDatabase getInstance(FirebaseApp var0, String var1) {
        if(TextUtils.isEmpty(var1)) {
            throw new DatabaseException("Failed to get FirebaseDatabase instance: Specify DatabaseURL within FirebaseApp or from your getInstance() call.");
        } else {
...
}

如果有人在 2021 年遇到此问题，只需按照以下步骤操作：- 在 build.gradle/app 中添加这些依赖项

  implementation platform('com.google.firebase:firebase-bom:26.3.0')
implementation 'com.google.firebase:firebase-database-ktx'

然后使用数据库引用对象

databaseReference=Firebase.database.getReference("Users")

仍然很困惑然后在这里阅读这个文档1 https://firebase.google.com/docs/database/android/start