sample(auth): full customization demo

[demolaf]

Preview

• Full Customization Flow

full-customization-flow.webm

• Other sign in methods via bottom sheet

other-sign-in-methods.webm

• Error Dialog (Inherits font change)

[gemini-code-assist]

Code Review

This pull request introduces a fully customized authentication flow demo (FullCustomizationDemoActivity and associated steps) to showcase the capabilities of customMethodPickerLayout in FirebaseAuthScreen, alongside minor inset adjustments in the default auth screens. The review feedback is highly constructive and should be addressed: it recommends implementing a BackHandler for proper step-back navigation, making the alternative sign-in methods sheet scrollable to prevent clipping on smaller screens, passing the FirebaseAuth instance dynamically to support custom configurations, performing case-insensitive and trimmed email validation, and ensuring the loading indicator in CtaButton has sufficient contrast.

[gemini-code-assist]

When the user is on the Login or SignUp step, pressing the system back button will exit the entire activity/screen instead of returning to the EnterEmail step. Adding a BackHandler when flowStep != FlowStep.EnterEmail intercepts the back press and routes the user back to the email entry step, matching standard Android navigation expectations.

    var flowStep by remember { mutableStateOf(FlowStep.EnterEmail) }
    var showOtherMethods by remember { mutableStateOf(false) }
    var isCheckingEmail by remember { mutableStateOf(false) }
    val coroutineScope = rememberCoroutineScope()

    // Password/confirmPassword are hoisted in EmailAuthContentState, not local to LoginStep/
    // SignUpStep — they survive a round trip back to EnterEmail, so a stale password typed for
    // one email could carry over if a different email also routes to the same step. Clear them
    // whenever the user backs out via "Use a different email".
    val onUseDifferentEmail: () -> Unit = {
        state.onPasswordChange("")
        state.onConfirmPasswordChange("")
        flowStep = FlowStep.EnterEmail
    }

    androidx.activity.compose.BackHandler(enabled = flowStep != FlowStep.EnterEmail) {
        onUseDifferentEmail()
    }

[gemini-code-assist]

With up to 9 alternative identity providers configured, the list of buttons and the Terms of Service footer will easily exceed the available screen height on smaller devices or in landscape orientation. Since the sheet's Column is not scrollable, this will cause content to be clipped and become inaccessible. Wrapping the column in a scrollable modifier (e.g., .verticalScroll(rememberScrollState())) ensures all options remain accessible.

        Column(
            modifier = Modifier
                .fillMaxWidth()
                .verticalScroll(androidx.compose.foundation.rememberScrollState())
                .padding(horizontal = 64.dp),
        ) {

[gemini-code-assist]

To support multi-app configurations or custom Firebase Auth instances (such as when using the emulator), avoid calling FirebaseAuth.getInstance() directly. Instead, pass the configured FirebaseAuth instance from the parent screen.

fun SingleFieldSignInUI(
    state: EmailAuthContentState,
    auth: FirebaseAuth,
    otherProviders: List<AuthProvider>,
    onProviderSelected: (AuthProvider) -> Unit,
    tosUrl: String?,
    ppUrl: String?,
)

[gemini-code-assist]

Pass the auth instance to fetchLegacySignInMethods.

Suggested change

	onContinue = {
	isCheckingEmail = true
	coroutineScope.launch {
	val signInMethods = fetchLegacySignInMethods(state.email)
	flowStep = if (signInMethods.isEmpty()) FlowStep.SignUp else FlowStep.Login
	isCheckingEmail = false
	}
	},
	onContinue = {
	isCheckingEmail = true
	coroutineScope.launch {
	val signInMethods = fetchLegacySignInMethods(auth, state.email)
	flowStep = if (signInMethods.isEmpty()) FlowStep.SignUp else FlowStep.Login
	isCheckingEmail = false
	}
	},

[gemini-code-assist]

Update fetchLegacySignInMethods to accept and use the passed FirebaseAuth instance instead of retrieving the default global instance.

private suspend fun fetchLegacySignInMethods(auth: FirebaseAuth, email: String): List<String> {
    return try {
        @Suppress("DEPRECATION")
        auth.fetchSignInMethodsForEmail(email)
            .await()
            .signInMethods
            ?.filter { it.isNotBlank() }
            ?: emptyList()
    } catch (e: Exception) {
        Log.w("SingleFieldSignInUI", "fetchSignInMethodsForEmail failed for $email", e)
        emptyList()
    }
}

[gemini-code-assist]

Pass authUI.auth to SingleFieldSignInUI to match the updated signature.

            ) { state ->
                SingleFieldSignInUI(
                    state = state,
                    auth = authUI.auth,
                    otherProviders = providers.filterNot { it is AuthProvider.Email },
                    onProviderSelected = onProviderSelected,
                    tosUrl = configuration.tosUrl,
                    ppUrl = configuration.privacyPolicyUrl,
                )
            }

[gemini-code-assist]

Email addresses should be compared case-insensitively and ignoring leading/trailing whitespace, as mobile keyboards often auto-capitalize the first letter or append spaces. Using equals(..., ignoreCase = true) and trim() prevents validation failures due to casing or accidental spacing differences.

Suggested change

	val emailsMatch = confirmEmail.isNotBlank() && confirmEmail == state.email
	val emailsMatch = confirmEmail.isNotBlank() && confirmEmail.trim().equals(state.email.trim(), ignoreCase = true)

[gemini-code-assist]

By default, CircularProgressIndicator uses the theme's primary color. Since CtaButton also uses the primary color as its default background, the progress indicator will have extremely low contrast or be completely invisible. Setting its color to LocalContentColor.current ensures it matches the button's text color (e.g., onPrimary) and remains clearly visible.

            if (isLoading) {
                CircularProgressIndicator(
                    modifier = Modifier.size(20.dp),
                    color = androidx.compose.material3.LocalContentColor.current
                )
            } else {