Android fix system prompt part (#100)

Author: kirklandsign

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

@@ -90,6 +90,7 @@ public class MainActivity extends AppCompatActivity implements Runnable, LlmCall
   private Executor executor;
   private boolean sawStartHeaderId = false;
   private String mAudioFileToPrefill;
+  private boolean shouldAddSystemPrompt = true;
 
   @Override
   public void onResult(String result) {
@@ -652,7 +653,8 @@ private int getInputImageSideSize() {
       case GEMMA_3:
         return 896;
       default:
-        throw new IllegalArgumentException("Unsupported model type: " + mCurrentSettingsFields.getModelType());
+        throw new IllegalArgumentException(
+            "Unsupported model type: " + mCurrentSettingsFields.getModelType());
     }
   }
 
@@ -774,7 +776,9 @@ private void onModelRunStopped() {
           addSelectedImagesToChatThread(mSelectedImageUri);
           String rawPrompt = mEditTextMessage.getText().toString();
           String finalPrompt =
-              mCurrentSettingsFields.getFormattedSystemAndUserPrompt(rawPrompt, mThinkMode);
+              (shouldAddSystemPrompt ? mCurrentSettingsFields.getFormattedSystemPrompt() : "")
+                  + mCurrentSettingsFields.getFormattedUserPrompt(rawPrompt, mThinkMode);
+          shouldAddSystemPrompt = false;
           // We store raw prompt into message adapter, because we don't want to show the extra
           // tokens from system prompt
           mMessageAdapter.add(new Message(rawPrompt, true, MessageType.TEXT, promptID));

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

@@ -18,14 +18,10 @@ public class PromptFormat {
 
   public static String getSystemPromptTemplate(ModelType modelType) {
     switch (modelType) {
-      case GEMMA_3:
-        return SYSTEM_PLACEHOLDER;
       case LLAMA_3:
         return "<|begin_of_text|><|start_header_id|>system<|end_header_id|>\n"
             + SYSTEM_PLACEHOLDER
             + "<|eot_id|>";
-      case LLAVA_1_5:
-        return "USER: ";
       case QWEN_3:
         return "<|im_start|>system\n" + "You are a helpful assistant.\n" + "<|im_end|>\n";
       default:
@@ -51,6 +47,7 @@ public static String getUserPromptTemplate(ModelType modelType) {
             + "<|im_start|>assistant\n"
             + THINKING_MODE_PLACEHOLDER;
       case LLAVA_1_5:
+        return "User: " + USER_PLACEHOLDER;
       default:
         return USER_PLACEHOLDER;
     }

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

@@ -38,10 +38,6 @@ public String getUserPrompt() {
     return userPrompt;
   }
 
-  public String getFormattedSystemAndUserPrompt(String prompt, boolean thinkingMode) {
-    return getFormattedSystemPrompt() + getFormattedUserPrompt(prompt, thinkingMode);
-  }
-
   public String getFormattedSystemPrompt() {
     return PromptFormat.getSystemPromptTemplate(modelType)
         .replace(PromptFormat.SYSTEM_PLACEHOLDER, systemPrompt);