Support offline Gemma model, fix scrollbar, and update build script

app/build.gradle.kts

@@ -1,5 +1,4 @@
 
-
 plugins {
     id("com.android.application")
     id("org.jetbrains.kotlin.android")
@@ -91,5 +90,10 @@ dependencies {
     implementation("com.google.ai.client.generativeai:generativeai:0.9.0")
     implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.0")
     implementation("androidx.localbroadcastmanager:localbroadcastmanager:1.1.0")
-}
 
+    // MediaPipe GenAI for offline inference (LLM)
+    implementation("com.google.mediapipe:tasks-genai:0.10.20")
+
+    // Camera Core to potentially fix missing JNI lib issue
+    implementation("androidx.camera:camera-core:1.4.0")
+}

app/src/main/kotlin/com/google/ai/sample/GenerativeAiViewModelFactory.kt

@@ -17,7 +17,13 @@ enum class ApiProvider {
     CEREBRAS
 }
 
-enum class ModelOption(val displayName: String, val modelName: String, val apiProvider: ApiProvider = ApiProvider.GOOGLE) {
+enum class ModelOption(
+    val displayName: String,
+    val modelName: String,
+    val apiProvider: ApiProvider = ApiProvider.GOOGLE,
+    val downloadUrl: String? = null,
+    val size: String? = null
+) {
     GPT_5_1_CODEX_MAX("GPT-5.1 Codex Max (Vercel)", "openai/gpt-5.1-codex-max", ApiProvider.VERCEL),
     GPT_5_1_CODEX_MINI("GPT-5.1 Codex Mini (Vercel)", "openai/gpt-5.1-codex-mini", ApiProvider.VERCEL),
     GPT_5_NANO("GPT-5 Nano (Vercel)", "openai/gpt-5-nano", ApiProvider.VERCEL),
@@ -30,7 +36,13 @@ enum class ModelOption(val displayName: String, val modelName: String, val apiPr
     GEMINI_FLASH("Gemini 2.0 Flash", "gemini-2.0-flash"),
     GEMINI_FLASH_LITE("Gemini 2.0 Flash Lite", "gemini-2.0-flash-lite"),
     GEMMA_3_27B_IT("Gemma 3 27B IT", "gemma-3-27b-it"),
-    GEMMA_3N_E4B_IT("Gemma 3n E4B it (online)", "gemma-3n-e4b-it")
+    GEMMA_3N_E4B_IT(
+        "Gemma 3n E4B it (offline)",
+        "gemma-3n-e4b-it",
+        ApiProvider.GOOGLE,
+        "https://huggingface.co/na5h13/gemma-3n-E4B-it-litert-lm/resolve/main/gemma-3n-E4B-it-int4.litertlm?download=true",
+        "4.92 GB"
+    )
 }
 
 val GenerativeViewModelFactory = object : ViewModelProvider.Factory {
@@ -73,6 +85,7 @@ val GenerativeViewModelFactory = object : ViewModelProvider.Factory {
                         )
 
                         val viewModel = PhotoReasoningViewModel(
+                            application,
                             fallbackModel, 
                             currentModel.modelName, 
                             liveApiManager
@@ -88,6 +101,7 @@ val GenerativeViewModelFactory = object : ViewModelProvider.Factory {
                             generationConfig = config
                         )
                         PhotoReasoningViewModel(
+                            application,
                             generativeModel, 
                             currentModel.modelName,
                             null // No LiveApiManager for regular models

app/src/main/kotlin/com/google/ai/sample/MainActivity.kt

@@ -381,12 +381,8 @@ class MainActivity : ComponentActivity() {
 
         apiKeyManager = ApiKeyManager.getInstance(this)
         Log.d(TAG, "onCreate: ApiKeyManager initialized.")
-        if (apiKeyManager.getApiKeys(ApiProvider.GOOGLE).isEmpty() && apiKeyManager.getApiKeys(ApiProvider.CEREBRAS).isEmpty()) {
-             showApiKeyDialog = true
-             Log.d(TAG, "onCreate: No API key found, showApiKeyDialog set to true.")
-        } else {
-             Log.d(TAG, "onCreate: API key found.")
-        }
+        // API key dialog logic removed from onCreate as requested.
+        // It will be triggered when needed (e.g., when the user tries to use an online model).
 
         // Log.d(TAG, "onCreate: Calling checkAndRequestPermissions.") // Deleted
         // checkAndRequestPermissions() // Deleted

app/src/main/kotlin/com/google/ai/sample/MenuScreen.kt

@@ -41,6 +41,10 @@ import android.Manifest // For Manifest.permission.POST_NOTIFICATIONS
 import androidx.compose.material3.AlertDialog // For the rationale dialog
 import androidx.compose.runtime.saveable.rememberSaveable
 import android.util.Log
+import android.os.Environment
+import android.os.StatFs
+import com.google.ai.sample.feature.multimodal.ModelDownloadManager
+import java.io.File
 
 data class MenuItem(
     val routeId: String,
@@ -67,6 +71,8 @@ fun MenuScreen(
     val currentModel = GenerativeAiViewModelFactory.getCurrentModel()
     var selectedModel by remember { mutableStateOf(currentModel) }
     var expanded by remember { mutableStateOf(false) }
+    var showDownloadDialog by remember { mutableStateOf(false) }
+    var downloadDialogModel by remember { mutableStateOf<ModelOption?>(null) }
 
     Column(
         modifier = Modifier
@@ -152,11 +158,24 @@ fun MenuScreen(
 
                                 orderedModels.forEach { modelOption ->
                                     DropdownMenuItem(
-                                        text = { Text(modelOption.displayName) },
+                                        text = {
+                                            Text(modelOption.displayName + (modelOption.size?.let { " - $it" } ?: ""))
+                                        },
                                         onClick = {
-                                            selectedModel = modelOption
-                                            GenerativeAiViewModelFactory.setModel(modelOption)
                                             expanded = false
+                                            if (modelOption == ModelOption.GEMMA_3N_E4B_IT) {
+                                                val isDownloaded = ModelDownloadManager.isModelDownloaded(context)
+                                                if (!isDownloaded) {
+                                                    downloadDialogModel = modelOption
+                                                    showDownloadDialog = true
+                                                } else {
+                                                    selectedModel = modelOption
+                                                    GenerativeAiViewModelFactory.setModel(modelOption)
+                                                }
+                                            } else {
+                                                selectedModel = modelOption
+                                                GenerativeAiViewModelFactory.setModel(modelOption)
+                                            }
                                         },
                                         enabled = true // Always enabled
                                     )
@@ -195,6 +214,19 @@ fun MenuScreen(
                                 } else {
                                     if (menuItem.routeId == "photo_reasoning") {
                                         val mainActivity = context as? MainActivity
+                                        val currentModel = GenerativeAiViewModelFactory.getCurrentModel()
+                                        // Check API Key for online models
+                                        if (currentModel.apiProvider != ApiProvider.GOOGLE || !currentModel.modelName.contains("litert")) { // Simple check, refine if needed. Actually offline model has specific Enum
+                                             if (currentModel != ModelOption.GEMMA_3N_E4B_IT) {
+                                                 val apiKey = mainActivity?.getCurrentApiKey(currentModel.apiProvider)
+                                                 if (apiKey.isNullOrEmpty()) {
+                                                     // Show API Key Dialog
+                                                     onApiKeyButtonClicked() // Or a specific callback to show dialog
+                                                     return@TextButton
+                                                 }
+                                             }
+                                        }
+
                                         if (mainActivity != null) { // Ensure mainActivity is not null
                                             if (!mainActivity.isNotificationPermissionGranted()) {
                                                 Log.d("MenuScreen", "Notification permission NOT granted.")
@@ -351,6 +383,41 @@ GPT-5 nano Input: $0.05/M Output: $0.40/M
             }
         )
     }
+
+    if (showDownloadDialog && downloadDialogModel != null) {
+        val context = LocalContext.current
+        val statFs = StatFs(Environment.getExternalStorageDirectory().path)
+        val bytesAvailable = statFs.availableBlocksLong * statFs.blockSizeLong
+        val gbAvailable = bytesAvailable.toDouble() / (1024 * 1024 * 1024)
+        val formattedGbAvailable = String.format("%.2f", gbAvailable)
+
+        AlertDialog(
+            onDismissRequest = { showDownloadDialog = false },
+            title = { Text("Download Model? (4.92 GB)") },
+            text = { Text("Should the Gemma 3n E4B be downloaded?\n\n$formattedGbAvailable GB of storage available.") },
+            confirmButton = {
+                TextButton(
+                    onClick = {
+                        showDownloadDialog = false
+                        downloadDialogModel?.downloadUrl?.let { url ->
+                            ModelDownloadManager.downloadModel(context, url)
+                            // We set the model, but the user will have to wait for download
+                            selectedModel = downloadDialogModel!!
+                            GenerativeAiViewModelFactory.setModel(downloadDialogModel!!)
+                        }
+                    }
+                ) { Text("OK") }
+            },
+            dismissButton = {
+                TextButton(
+                    onClick = {
+                        showDownloadDialog = false
+                        // Do not change model
+                    }
+                ) { Text("ABORT") }
+            }
+        )
+    }
 }
 
 @Preview(showSystemUi = true)

app/src/main/kotlin/com/google/ai/sample/feature/multimodal/ModelDownloadManager.kt

@@ -0,0 +1,82 @@
+package com.google.ai.sample.feature.multimodal
+
+import android.app.DownloadManager
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.database.Cursor
+import android.net.Uri
+import android.util.Log
+import android.widget.Toast
+import java.io.File
+
+object ModelDownloadManager {
+    private const val TAG = "ModelDownloadManager"
+    const val MODEL_FILENAME = "gemma-3n-e4b-it-int4.litertlm"
+    private var downloadId: Long = -1
+
+    fun isModelDownloaded(context: Context): Boolean {
+        val file = getModelFile(context)
+        return file != null && file.exists() && file.length() > 0
+    }
+
+    fun getModelFile(context: Context): File? {
+        val externalFilesDir = context.getExternalFilesDir(null)
+        return if (externalFilesDir != null) {
+            File(externalFilesDir, MODEL_FILENAME)
+        } else {
+            Log.e(TAG, "External files directory is not available.")
+            null
+        }
+    }
+
+    fun downloadModel(context: Context, url: String) {
+        if (isModelDownloaded(context)) {
+            Toast.makeText(context, "Model already downloaded.", Toast.LENGTH_SHORT).show()
+            return
+        }
+
+        val file = getModelFile(context)
+        if (file != null && file.exists()) {
+            file.delete() // Clean up partial or old file
+        }
+
+        try {
+            val request = DownloadManager.Request(Uri.parse(url))
+                .setTitle("Downloading Gemma Model")
+                .setDescription("Downloading offline AI model (4.92 GB)...")
+                .setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED)
+                .setDestinationInExternalFilesDir(context, null, MODEL_FILENAME)
+                .setAllowedOverMetered(true)
+                .setAllowedOverRoaming(true)
+
+            val downloadManager = context.getSystemService(Context.DOWNLOAD_SERVICE) as? DownloadManager
+
+            if (downloadManager != null) {
+                downloadId = downloadManager.enqueue(request)
+                Toast.makeText(context, "Download started. Please do not pause the download, as it cannot be resumed.", Toast.LENGTH_LONG).show()
+                Log.d(TAG, "Download started with ID: $downloadId")
+            } else {
+                Log.e(TAG, "DownloadManager service not available.")
+                Toast.makeText(context, "Download service unavailable.", Toast.LENGTH_SHORT).show()
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Error starting download: ${e.message}")
+            Toast.makeText(context, "Failed to start download.", Toast.LENGTH_SHORT).show()
+        }
+    }
+
+    fun cancelDownload(context: Context) {
+        if (downloadId != -1L) {
+            val downloadManager = context.getSystemService(Context.DOWNLOAD_SERVICE) as? DownloadManager
+            if (downloadManager != null) {
+                downloadManager.remove(downloadId)
+                downloadId = -1
+                Toast.makeText(context, "Download cancelled.", Toast.LENGTH_SHORT).show()
+            } else {
+                Log.e(TAG, "DownloadManager service not available for cancellation.")
+            }
+        }
+    }
+}