错误：请确保先调用FacebookSdk.sdkInitialize（）

Question

I've never had to use FacebookSdk.sdkInitialize() but for some reason I'm getting an error now on my setContentView(R.layout.activity_main) in MainActivity onCreate() :

Error inflating class com.facebook.login.widget.LoginButton

Caused by: The SDK has not been initialized, make sure to call FacebookSdk.sdkInitialize() first.

At the exact same time I also recieved the error Make sure to call FirebaseApp.initializeApp(Context) first before accessing FirebaseFirestore.getInstance() - an error I've never seen before.

They must be related in a way but I'm not sure what the problem is.

class MainActivity : AppCompatActivity() {

    val callbackManager = CallbackManager.Factory.create()
    val db = FirebaseFirestore.getInstance()
    private lateinit var auth: FirebaseAuth

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val dbSettings = FirebaseFirestoreSettings.Builder().setPersistenceEnabled(false).build()
        db.firestoreSettings = dbSettings
        auth = FirebaseAuth.getInstance()
        setContentView(R.layout.activity_main)

Answer 1

Change declaration position.

class MainActivity : AppCompatActivity() {
    private lateinit var auth: FirebaseAuth

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val callbackManager = CallbackManager.Factory.create()
        val db = FirebaseFirestore.getInstance()
        val dbSettings = FirebaseFirestoreSettings.Builder().setPersistenceEnabled(false).build()
        db.firestoreSettings = dbSettings
        auth = FirebaseAuth.getInstance()

or You can use :

class MainActivity : AppCompatActivity() {
    private lateinit var auth: FirebaseAuth
    val db : FirebaseFirestore
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val callbackManager = CallbackManager.Factory.create()
        db = FirebaseFirestore.getInstance()
        val dbSettings = FirebaseFirestoreSettings.Builder().setPersistenceEnabled(false).build()
        db.firestoreSettings = dbSettings
        auth = FirebaseAuth.getInstance()