Firebase 数据库 getInstance 导致应用程序崩溃

Question

创建 google-service.json 后运行示例时，应用在尝试在 SignInActivity 中获取数据库引用时崩溃

mDatabase = FirebaseDatabase.getInstance().getReference();

崩溃日志

05-21 09:27:27.644 488-488/com.google.firebase.quickstart.database D/AndroidRuntime: Shutting down VM
05-21 09:27:27.644 488-488/com.google.firebase.quickstart.database E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                     Process: com.google.firebase.quickstart.database, PID: 488
                                                                                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.google.firebase.quickstart.database/com.google.firebase.quickstart.database.SignInActivity}: com.google.firebase.database.DatabaseException: Failed to get 

FirebaseDatabase instance: FirebaseApp object has no DatabaseURL in its FirebaseOptions object.
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
     at android.app.ActivityThread.access$800(ActivityThread.java:151)
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
     at android.os.Handler.dispatchMessage(Handler.java:102)
     at android.os.Looper.loop(Looper.java:135)
     at android.app.ActivityThread.main(ActivityThread.java:5254)
     at java.lang.reflect.Method.invoke(Native Method)
     at java.lang.reflect.Method.invoke(Method.java:372)
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
  Caused by: com.google.firebase.database.DatabaseException: Failed to get FirebaseDatabase instance: FirebaseApp object has no DatabaseURL in its FirebaseOptions object.
     at com.google.firebase.database.FirebaseDatabase.getInstance(Unknown Source)
     at com.google.firebase.database.FirebaseDatabase.getInstance(Unknown Source)
     at com.google.firebase.quickstart.database.SignInActivity.onCreate(SignInActivity.java:39)
     at android.app.Activity.performCreate(Activity.java:5990)
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
     at android.app.ActivityThread.access$800(ActivityThread.java:151) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:135) 
     at android.app.ActivityThread.main(ActivityThread.java:5254) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:372) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 

如何解决这个问题？

Answer 1

从 Firebase console 中的项目设置下载 google-services.json 。我的错误是从https://developers.google.com/mobile/add下载它.