java.lang.IllegalStateException : Default FirebaseApp is not initialized in this process com. example.bottomnav

Question

我制作了包含 Firebase 身份验证的应用程序的基本版本，在将应用程序与 firebase 连接之前，我在 Android 模拟器中测试了该应用程序。我收到以下错误，然后我自己修复了一些东西。
- 连接火力基地
-添加了依赖 classpath 'com.google.gms:google-services:4.2.0'仍然遇到以下错误-

/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.bottomnav, PID: 2049
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bottomnav/com.example.bottomnav.login}: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.bottomnav. Make sure to call FirebaseApp.initializeApp(Context) first.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.bottomnav. Make sure to call FirebaseApp.initializeApp(Context) first.
        at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@19.3.0:184)
        at com.google.firebase.auth.FirebaseAuth.getInstance(com.google.firebase:firebase-auth@@19.3.1:1)
        at com.example.bottomnav.login.onCreate(login.java:40)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)

我在早期的项目中使用过 Firebase 工具，我的印象是使用 Android Studio 中的内置 firebase 工具可以自动完成所有工作。那么，有没有我可能跳过的步骤？

Answer 1

对我来说，问题是使用谷歌服务插件版本 4.3.9。只是
改变

        classpath 'com.google.gms:google-services:4.3.9'  

至

       classpath 'com.google.gms:google-services:4.3.8'