fix(sample): address review feedback on full customization demo

Intercept back on the login/sign-up steps so it returns to email entry
instead of leaving the auth flow, make the other-sign-in-methods sheet
scrollable (nine providers plus the ToS footer overflow shorter screens),
compare the confirmation email trimmed and case-insensitively and give the
field an email keyboard, and take the configured FirebaseAuth instance
rather than reaching for the global default.

Author: demolaf

app/src/main/java/com/firebaseui/android/demo/auth/fullcustomization/FullCustomizationDemoActivity.kt

@@ -173,6 +173,7 @@ private fun MainUI(
             ) { state ->
                 AuthMethodPickerUI(
                     state = state,
+                    auth = authUI.auth,
                     otherProviders = providers.filterNot { it is AuthProvider.Email },
                     onProviderSelected = onProviderSelected,
                     tosUrl = configuration.tosUrl,

app/src/main/java/com/firebaseui/android/demo/auth/fullcustomization/common/CtaButton.kt

@@ -45,6 +45,11 @@ fun CtaButton(
                 .height(80.dp),
         ) {
             if (isLoading) {
+                // Left on the M3 default (colorScheme.primary). Every caller passes
+                // `enabled = ... && !isLoading`, so the button is disabled exactly while the
+                // spinner shows: the container is the translucent disabled fill, and primary
+                // reads clearly against it. Using LocalContentColor here would instead pick up
+                // disabledContentColor (onSurface at 38%) and wash the spinner out.
                 CircularProgressIndicator(modifier = Modifier.size(20.dp))
             } else {
                 Text(text = text, style = MaterialTheme.typography.titleMedium)

app/src/main/java/com/firebaseui/android/demo/auth/fullcustomization/common/OtherSignInMethodsSheet.kt

@@ -6,6 +6,8 @@ import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.ModalBottomSheet
@@ -32,9 +34,12 @@ fun OtherSignInMethodsSheet(
         onDismissRequest = onDismissRequest,
         containerColor = MaterialTheme.colorScheme.primaryContainer,
     ) {
+        // Scrollable: the demo offers nine alternative providers plus the ToS footer, which
+        // overflows a bottom sheet on shorter screens and in landscape.
         Column(
             modifier = Modifier
                 .fillMaxWidth()
+                .verticalScroll(rememberScrollState())
                 .padding(horizontal = 64.dp),
         ) {
             Text(

app/src/main/java/com/firebaseui/android/demo/auth/fullcustomization/screens/AuthMethodPickerUI.kt

@@ -1,6 +1,7 @@
 package com.firebaseui.android.demo.auth.fullcustomization.screens
 
 import android.util.Log
+import androidx.activity.compose.BackHandler
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.Composable
@@ -25,6 +26,7 @@ private enum class FlowStep { EnterEmail, Login, SignUp }
 @Composable
 fun AuthMethodPickerUI(
     state: EmailAuthContentState,
+    auth: FirebaseAuth,
     otherProviders: List<AuthProvider>,
     onProviderSelected: (AuthProvider) -> Unit,
     tosUrl: String?,
@@ -45,6 +47,10 @@ fun AuthMethodPickerUI(
         flowStep = FlowStep.EnterEmail
     }
 
+    // customMethodPickerLayout is the NavHost's start destination and these steps are local
+    // state, so without this the system back press would leave the auth flow entirely.
+    BackHandler(enabled = flowStep != FlowStep.EnterEmail) { onUseDifferentEmail() }
+
     Box(modifier = Modifier.fillMaxSize()) {
         when (flowStep) {
             FlowStep.EnterEmail -> EmailEntryStep(
@@ -54,7 +60,7 @@ fun AuthMethodPickerUI(
                 onContinue = {
                     isCheckingEmail = true
                     coroutineScope.launch {
-                        val signInMethods = fetchLegacySignInMethods(state.email)
+                        val signInMethods = fetchLegacySignInMethods(auth, state.email)
                         flowStep = if (signInMethods.isEmpty()) FlowStep.SignUp else FlowStep.Login
                         isCheckingEmail = false
                     }
@@ -90,11 +96,10 @@ fun AuthMethodPickerUI(
  * deprecated by Firebase ("legacy") and, depending on the project's Email Enumeration Protection
  * setting, may always return an empty list regardless of whether the email exists.
  */
-private suspend fun fetchLegacySignInMethods(email: String): List<String> {
+private suspend fun fetchLegacySignInMethods(auth: FirebaseAuth, email: String): List<String> {
     return try {
         @Suppress("DEPRECATION")
-        FirebaseAuth.getInstance()
-            .fetchSignInMethodsForEmail(email)
+        auth.fetchSignInMethodsForEmail(email)
             .await()
             .signInMethods
             ?.filter { it.isNotBlank() }

app/src/main/java/com/firebaseui/android/demo/auth/fullcustomization/screens/email/pages/SignUpStep.kt

@@ -14,6 +14,7 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.safeDrawingPadding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.text.KeyboardOptions
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.MaterialTheme
@@ -29,6 +30,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.input.KeyboardType
 import androidx.compose.ui.text.input.PasswordVisualTransformation
 import androidx.compose.ui.unit.dp
 import com.firebase.ui.auth.ui.screens.email.EmailAuthContentState
@@ -61,7 +63,10 @@ fun SignUpStep(
     var lastName by remember { mutableStateOf("") }
     var confirmEmail by remember { mutableStateOf("") }
 
-    val emailsMatch = confirmEmail.isNotBlank() && confirmEmail == state.email
+    // Compared case-insensitively and trimmed: this field uses the default keyboard, which
+    // auto-capitalises on many IMEs, so an exact match would reject the user's own address.
+    val emailsMatch = confirmEmail.isNotBlank() &&
+        confirmEmail.trim().equals(state.email.trim(), ignoreCase = true)
     val passwordsMatch = state.confirmPassword.isNotBlank() && state.confirmPassword == state.password
     val canSignUp = firstName.isNotBlank() &&
         lastName.isNotBlank() &&
@@ -153,6 +158,9 @@ fun SignUpStep(
                                     onValueChange = { confirmEmail = it },
                                     label = "Confirm Email",
                                     enabled = !state.isLoading,
+                                    keyboardOptions = KeyboardOptions(
+                                        keyboardType = KeyboardType.Email,
+                                    ),
                                     isError = confirmEmail.isNotBlank() && !emailsMatch,
                                     supportingText = if (confirmEmail.isNotBlank() && !emailsMatch) {
                                         "Emails don't match"