title: Can't use FirebaseUI with fragments
body: <p>I'm trying to implement FirebaseAuth UI to my app, but I've ran into some issues.</p>
  
  <p>I'm trying to create the FirebaseUIActivity.kt as a fragment, but when I call the support fragment manager it crashes. </p>
  
  <pre><code>  supportFragmentManager.beginTransaction().replace(R.id.fragment_container, FirebaseUIActivity.newInstance()).commit()
  </code></pre>
  
  <p>Here is some code:</p>
  
  <p>MainActivity.kt</p>
  
  <pre><code>class MainActivity : AppCompatActivity() {
  
  private lateinit var binding: ActivityMainBinding
  
  override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
  
      binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
  
      // Support toolbar
      setSupportActionBar(binding.toolbar)
  
      supportFragmentManager.beginTransaction().replace(R.id.fragment_container, FirebaseUIActivity.newInstance()).commit()
      }
  
  }
  </code></pre>
  
  <p>FirebaseUiActivity.kt</p>
  
  <pre><code>class FirebaseUIActivity : Fragment() {
  // Choose authentication providers
  
  companion object {
      fun newInstance() = FirebaseUIActivity()
  }
  
  override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
  }
  
  override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
      val binding: FirebaseUiFragmentBinding = DataBindingUtil.inflate(inflater, R.layout.firebase_ui_fragment, container, false)
  
      return binding.root
  
  }
  
  override fun onResume() {
      super.onResume()
  }
  private val providers = arrayListOf(
      AuthUI.IdpConfig.EmailBuilder().build(),
      AuthUI.IdpConfig.GoogleBuilder().build()
  )
  
  override fun startActivityForResult(intent: Intent?, requestCode: Int) {
      super.startActivityForResult(intent, requestCode)
  
      AuthUI.getInstance().createSignInIntentBuilder()
          .setAvailableProviders(providers)
          .build()
  
      }
  }
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>     Caused by: java.lang.IllegalStateException: Check your google-services plugin configuration, the default_web_client_id string wasn't populated.
      at com.firebase.ui.auth.util.Preconditions.checkConfigured(Preconditions.java:90)
      at com.firebase.ui.auth.AuthUI$IdpConfig$GoogleBuilder.&lt;init&gt;(AuthUI.java:957)
      at com.example.katzinbetihot.Firebase.FirebaseUIActivity.&lt;init&gt;(FirebaseUIActivity.kt:40)
      at com.example.katzinbetihot.Firebase.FirebaseUIActivity$Companion.newInstance(FirebaseUIActivity.kt:21)
      at com.example.katzinbetihot.main.MainActivity.onCreate(MainActivity.kt:24)
      at android.app.Activity.performCreate(Activity.java:7149)
      at android.app.Activity.performCreate(Activity.java:7140)
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1288)
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3031)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3191) 
      at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
      at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
      at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1920) 
      at android.os.Handler.dispatchMessage(Handler.java:106) 
      at android.os.Looper.loop(Looper.java:193) 
      at android.app.ActivityThread.main(ActivityThread.java:6912) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:537) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
  </code></pre>
  
  <p>Thanks for your help in advance, Emek!</p>