Revert "[Android] Enable multi-model selection and fix Gemma image prefill"

This reverts commit 4ccc896.

Author: kirklandsign

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ModuleSettings.kt

@@ -12,7 +12,7 @@ package com.example.executorchllamademo
  * Holds module-specific settings for the current model/tokenizer configuration.
  */
 data class ModuleSettings(
-    val modelFilePath: List<String> = emptyList(),
+    val modelFilePath: String = "",
     val tokenizerFilePath: String = "",
     val dataPath: String = "",
     val temperature: Double = DEFAULT_TEMPERATURE,

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/PromptFormat.kt

@@ -93,21 +93,6 @@ object PromptFormat {
         return "USER: $USER_PLACEHOLDER ASSISTANT:"
     }
 
-    @JvmStatic
-    fun getGemmaPreImagePrompt(): String {
-        return "<start_of_turn>user\n"
-    }
-
-    @JvmStatic
-    fun getGemmaPostImagePrompt(): String {
-        return "<end_of_image>"
-    }
-
-    @JvmStatic
-    fun getGemmaMultimodalUserPrompt(): String {
-        return "$USER_PLACEHOLDER<end_of_turn>\n<start_of_turn>model"
-    }
-
     @JvmStatic
     fun getFormattedLlamaGuardPrompt(userPrompt: String): String {
         return getUserPromptTemplate(ModelType.LLAMA_GUARD_3)

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ui/screens/ModelSettingsScreen.kt

@@ -439,12 +439,12 @@ private fun ModelDialog(viewModel: ModelSettingsViewModel) {
                 }
             )
         } else {
-            MultiChoiceDialog(
+            SingleChoiceDialog(
                 title = "Select model path",
                 options = viewModel.modelFiles.toList(),
-                selectedOptions = viewModel.moduleSettings.modelFilePath,
                 onSelect = { selected ->
-                    viewModel.toggleModel(selected)
+                    viewModel.selectModel(selected)
+                    viewModel.showModelDialog = false
                 },
                 onDismiss = { viewModel.showModelDialog = false }
             )
@@ -658,51 +658,6 @@ private fun InvalidPromptDialog(viewModel: ModelSettingsViewModel) {
     }
 }
 
-@Composable
-private fun MultiChoiceDialog(
-    title: String,
-    options: List<String>,
-    selectedOptions: List<String>,
-    onSelect: (String) -> Unit,
-    onDismiss: () -> Unit
-) {
-    AlertDialog(
-        onDismissRequest = onDismiss,
-        title = { Text(title) },
-        text = {
-            Column {
-                options.forEach { option ->
-                    val isSelected = selectedOptions.contains(option)
-                    Row(
-                        modifier = Modifier
-                            .fillMaxWidth()
-                            .clickable { onSelect(option) }
-                            .padding(vertical = 8.dp),
-                        verticalAlignment = Alignment.CenterVertically
-                    ) {
-                        androidx.compose.material3.Checkbox(
-                            checked = isSelected,
-                            onCheckedChange = { onSelect(option) }
-                        )
-                        Text(
-                            text = option.substringAfterLast('/'),
-                            modifier = Modifier
-                                .padding(start = 8.dp)
-                                .weight(1f),
-                            fontSize = 14.sp
-                        )
-                    }
-                }
-            }
-        },
-        confirmButton = {
-            TextButton(onClick = onDismiss) {
-                Text("Done")
-            }
-        }
-    )
-}
-
 @Composable
 private fun SingleChoiceDialog(
     title: String,

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ui/viewmodel/ChatViewModel.kt

@@ -185,23 +185,22 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
     }
 
     private fun loadLocalModelAndParameters(
-        modelFilePaths: List<String>,
+        modelFilePath: String,
         tokenizerFilePath: String,
         dataPath: String,
         temperature: Float
     ) {
         Thread {
-            setLocalModel(modelFilePaths, tokenizerFilePath, dataPath, temperature)
+            setLocalModel(modelFilePath, tokenizerFilePath, dataPath, temperature)
         }.start()
     }
 
     private fun setLocalModel(
-        modelPaths: List<String>,
+        modelPath: String,
         tokenizerPath: String,
         dataPath: String,
         temperature: Float
     ) {
-        val modelPath = modelPaths.joinToString(separator = ",")
         val modelLoadingMessage = Message("Loading model...", false, MessageType.SYSTEM, 0)
         ETLogging.getInstance().log(
             "Loading model $modelPath with tokenizer $tokenizerPath data path $dataPath"
@@ -346,7 +345,6 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
                             img.height,
                             ModelUtils.VISION_MODEL_IMAGE_CHANNELS
                         )
-                        module?.prefillPrompt(PromptFormat.getGemmaPostImagePrompt())
                     }
                 }
             }
@@ -387,9 +385,6 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
         } else if (currentSettingsFields.modelType == ModelType.GEMMA_3 && _selectedImages.isNotEmpty()) {
             finalPrompt = PromptFormat.getGemmaMultimodalUserPrompt()
                 .replace(PromptFormat.USER_PLACEHOLDER, rawPrompt)
-        } else if (currentSettingsFields.modelType == ModelType.GEMMA_3 && _selectedImages.isNotEmpty()) {
-            finalPrompt = PromptFormat.getGemmaMultimodalUserPrompt()
-                .replace(PromptFormat.USER_PLACEHOLDER, rawPrompt)
         } else {
             finalPrompt = (if (shouldAddSystemPrompt) currentSettingsFields.getFormattedSystemPrompt() else "") +
                     currentSettingsFields.getFormattedUserPrompt(rawPrompt, thinkMode)

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ui/viewmodel/ModelSettingsViewModel.kt

@@ -86,7 +86,7 @@ class ModelSettingsViewModel : ViewModel() {
     private fun applyBackendDefaults(settings: ModuleSettings): ModuleSettings {
         return if (settings.backendType == BackendType.MEDIATEK) {
             settings.copy(
-                modelFilePath = if (settings.modelFilePath.isEmpty()) listOf("/in/mtk/llama/runner") else settings.modelFilePath,
+                modelFilePath = settings.modelFilePath.ifEmpty { "/in/mtk/llama/runner" },
                 tokenizerFilePath = settings.tokenizerFilePath.ifEmpty { "/in/mtk/llama/runner" }
             )
         } else {
@@ -95,18 +95,9 @@ class ModelSettingsViewModel : ViewModel() {
     }
 
     // Model selection
-    fun toggleModel(modelPath: String) {
-        val currentModels = moduleSettings.modelFilePath.toMutableList()
-        if (currentModels.contains(modelPath)) {
-            currentModels.remove(modelPath)
-        } else {
-            currentModels.add(modelPath)
-        }
-        var newSettings = moduleSettings.copy(modelFilePath = currentModels)
-        // Auto-select type based on the last added model or the first one
-        if (currentModels.isNotEmpty()) {
-             newSettings = autoSelectModelType(newSettings, modelPath)
-        }
+    fun selectModel(modelPath: String) {
+        var newSettings = moduleSettings.copy(modelFilePath = modelPath)
+        newSettings = autoSelectModelType(newSettings, modelPath)
         moduleSettings = newSettings
     }
 
@@ -202,10 +193,6 @@ class ModelSettingsViewModel : ViewModel() {
         return if (path.isEmpty()) "" else path.substringAfterLast('/')
     }
 
-    fun getFilenameFromPath(paths: List<String>): String {
-        return if (paths.isEmpty()) "" else paths.joinToString(", ") { it.substringAfterLast('/') }
-    }
-
     // Appearance mode selection (app-wide setting)
     fun selectAppearanceMode(mode: AppearanceMode) {
         appSettings = appSettings.copy(appearanceMode = mode)