FirebaseUI-Android: java.lang.ClassNotFoundException: com.firebase.ui.auth.data.model.FlowParameters

Step 1:

When trying to get the Auth UI going:

        Intent intent = AuthUI.getInstance()
                    .createSignInIntentBuilder()
                    .setTheme(R.style.SplashTheme)
                    .setAvailableProviders(idpConfigs)
                    .setTosAndPrivacyPolicyUrls(getString(R.string.terms_url), getString(R.string.privacy_url))
                    .setIsSmartLockEnabled(!BuildConfig.DEBUG)
                    .build();
        startActivityForResult(intent, RC_FIREBASE_UI_SIGNIN);

I see the following behaviour:

• if idpConfigs contains exactly one item, it correctly proceeds to the one login method
• if idpConfigs contains more than one item, the AuthMethodPickerActivity is displayed WITHOUT any of the login buttons (but it correctly shows the ToS/PP at the bottom)

Looking through the logs, I see this error:

08-23 21:01:07.343 1358-2025/? E/Parcel: Class not found when unmarshalling: com.firebase.ui.auth.data.model.FlowParameters
    java.lang.ClassNotFoundException: com.firebase.ui.auth.data.model.FlowParameters
        at java.lang.Class.classForName(Native Method)
        at java.lang.Class.forName(Class.java:453)
        at android.os.Parcel.readParcelableCreator(Parcel.java:2835)
        at android.os.Parcel.readParcelable(Parcel.java:2789)
        at android.os.Parcel.readValue(Parcel.java:2692)
        at android.os.Parcel.readArrayMapInternal(Parcel.java:3059)
        at android.os.BaseBundle.unparcel(BaseBundle.java:257)
        at android.os.BaseBundle.getString(BaseBundle.java:1086)
        at android.content.Intent.getStringExtra(Intent.java:7706)
        at com.android.server.am.ActivityStarter.startActivity(ActivityStarter.java:458)
        at com.android.server.am.ActivityStarter.startActivityLocked(ActivityStarter.java:409)
        at com.android.server.am.ActivityStarter.startActivityMayWait(ActivityStarter.java:1270)
        at com.android.server.am.ActivityManagerService.startActivityAsUser(ActivityManagerService.java:6053)
        at com.android.server.am.ActivityManagerService.startActivity(ActivityManagerService.java:5906)
        at android.app.IActivityManager$Stub.onTransact(IActivityManager.java:121)
        at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:3887)
        at android.os.Binder.execTransact(Binder.java:682)
     Caused by: java.lang.ClassNotFoundException: com.firebase.ui.auth.data.model.FlowParameters
        at java.lang.Class.classForName(Native Method)
        at java.lang.BootClassLoader.findClass(ClassLoader.java:1355)
        at java.lang.BootClassLoader.loadClass(ClassLoader.java:1415)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at java.lang.Class.classForName(Native Method) 
        at java.lang.Class.forName(Class.java:453) 
        at android.os.Parcel.readParcelableCreator(Parcel.java:2835) 
        at android.os.Parcel.readParcelable(Parcel.java:2789) 
        at android.os.Parcel.readValue(Parcel.java:2692) 
        at android.os.Parcel.readArrayMapInternal(Parcel.java:3059) 
        at android.os.BaseBundle.unparcel(BaseBundle.java:257) 
        at android.os.BaseBundle.getString(BaseBundle.java:1086) 
        at android.content.Intent.getStringExtra(Intent.java:7706) 
        at com.android.server.am.ActivityStarter.startActivity(ActivityStarter.java:458) 
        at com.android.server.am.ActivityStarter.startActivityLocked(ActivityStarter.java:409) 
        at com.android.server.am.ActivityStarter.startActivityMayWait(ActivityStarter.java:1270) 
        at com.android.server.am.ActivityManagerService.startActivityAsUser(ActivityManagerService.java:6053) 
        at com.android.server.am.ActivityManagerService.startActivity(ActivityManagerService.java:5906) 
        at android.app.IActivityManager$Stub.onTransact(IActivityManager.java:121) 
        at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:3887) 
        at android.os.Binder.execTransact(Binder.java:682) 
     Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack trace available
08-23 21:01:07.343 1358-2025/? W/Bundle: Failed to parse Bundle, but defusing quietly
    android.os.BadParcelableException: ClassNotFoundException when unmarshalling: com.firebase.ui.auth.data.model.FlowParameters
        at android.os.Parcel.readParcelableCreator(Parcel.java:2863)
        at android.os.Parcel.readParcelable(Parcel.java:2789)
        at android.os.Parcel.readValue(Parcel.java:2692)
        at android.os.Parcel.readArrayMapInternal(Parcel.java:3059)
        at android.os.BaseBundle.unparcel(BaseBundle.java:257)
        at android.os.BaseBundle.getString(BaseBundle.java:1086)
        at android.content.Intent.getStringExtra(Intent.java:7706)
        at com.android.server.am.ActivityStarter.startActivity(ActivityStarter.java:458)
        at com.android.server.am.ActivityStarter.startActivityLocked(ActivityStarter.java:409)
        at com.android.server.am.ActivityStarter.startActivityMayWait(ActivityStarter.java:1270)
        at com.android.server.am.ActivityManagerService.startActivityAsUser(ActivityManagerService.java:6053)
        at com.android.server.am.ActivityManagerService.startActivity(ActivityManagerService.java:5906)
        at android.app.IActivityManager$Stub.onTransact(IActivityManager.java:121)
        at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:3887)
        at android.os.Binder.execTransact(Binder.java:682)

Which would explain the issue. Here’s the relevant snippet of my build.gradle:

    // Play Services
    implementation "com.google.android.gms:play-services-auth:15.0.1"
    implementation "com.google.android.gms:play-services-base:15.0.1"
    implementation "com.google.android.gms:play-services-appinvite:15.0.1"
    implementation "com.google.android.gms:play-services-gcm:15.0.1"
    implementation "com.google.android.gms:play-services-location:15.0.1"
    implementation "com.google.android.gms:play-services-places:15.0.1"
    implementation "com.google.android.gms:play-services-ads:15.0.1"

    // Firebase
    implementation "com.google.firebase:firebase-core:16.0.0"
    implementation "com.google.firebase:firebase-auth:16.0.1"
    implementation "com.google.firebase:firebase-database:16.0.1"
    implementation "com.google.firebase:firebase-storage:16.0.1"
    implementation "com.google.firebase:firebase-crash:16.0.1"
    implementation "com.google.firebase:firebase-messaging:17.3.0"
    implementation "com.google.firebase:firebase-config:16.0.0"
    implementation "com.google.firebase:firebase-invites:16.0.1"
    implementation "com.google.firebase:firebase-perf:16.1.0"
    implementation 'com.firebaseui:firebase-ui:4.1.0'

This used to work, but I guess it broke with a recent update of FirebaseUI.

Step 2: Describe your environment

• Android device: S9+
• Android OS version: 8.0.0
• Google Play Services version: 12.8.74
• Firebase/Play Services SDK version: 15.0.1
• FirebaseUI version: 4.1.0