android: routine maintenance - Dec 2025 (#18338)

* Fix `msg` typo

* Fix thread safety in destroy() to support generation abortion in lifecycle callbacks.

* UI polish: stack new message change from below; fix GGUF margin not in view port

* Bug fixes: rare racing condition when main thread updating view and and default thread updating messages at the same time; user input not disabled during generation.

* Bump dependencies' versions; Deprecated outdated dsl usage.

examples/llama.android/app/src/main/java/com/example/llama/MainActivity.kt

@@ -6,6 +6,7 @@ import android.util.Log
 import android.widget.EditText
 import android.widget.TextView
 import android.widget.Toast
+import androidx.activity.addCallback
 import androidx.activity.enableEdgeToEdge
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.appcompat.app.AppCompatActivity
@@ -18,6 +19,7 @@ import com.arm.aichat.gguf.GgufMetadata
 import com.arm.aichat.gguf.GgufMetadataReader
 import com.google.android.material.floatingactionbutton.FloatingActionButton
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.onCompletion
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -36,6 +38,7 @@ class MainActivity : AppCompatActivity() {
 
     // Arm AI Chat inference engine
     private lateinit var engine: InferenceEngine
+    private var generationJob: Job? = null
 
     // Conversation states
     private var isModelReady = false
@@ -47,11 +50,13 @@ class MainActivity : AppCompatActivity() {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContentView(R.layout.activity_main)
+        // View model boilerplate and state management is out of this basic sample's scope
+        onBackPressedDispatcher.addCallback { Log.w(TAG, "Ignore back press for simplicity") }
 
         // Find views
         ggufTv = findViewById(R.id.gguf)
         messagesRv = findViewById(R.id.messages)
-        messagesRv.layoutManager = LinearLayoutManager(this)
+        messagesRv.layoutManager = LinearLayoutManager(this).apply { stackFromEnd = true }
         messagesRv.adapter = messageAdapter
         userInputEt = findViewById(R.id.user_input)
         userActionFab = findViewById(R.id.fab)
@@ -157,33 +162,35 @@ class MainActivity : AppCompatActivity() {
      * Validate and send the user message into [InferenceEngine]
      */
     private fun handleUserInput() {
-        userInputEt.text.toString().also { userSsg ->
-            if (userSsg.isEmpty()) {
+        userInputEt.text.toString().also { userMsg ->
+            if (userMsg.isEmpty()) {
                 Toast.makeText(this, "Input message is empty!", Toast.LENGTH_SHORT).show()
             } else {
                 userInputEt.text = null
+                userInputEt.isEnabled = false
                 userActionFab.isEnabled = false
 
                 // Update message states
-                messages.add(Message(UUID.randomUUID().toString(), userSsg, true))
+                messages.add(Message(UUID.randomUUID().toString(), userMsg, true))
                 lastAssistantMsg.clear()
                 messages.add(Message(UUID.randomUUID().toString(), lastAssistantMsg.toString(), false))
 
-                lifecycleScope.launch(Dispatchers.Default) {
-                    engine.sendUserPrompt(userSsg)
+                generationJob = lifecycleScope.launch(Dispatchers.Default) {
+                    engine.sendUserPrompt(userMsg)
                         .onCompletion {
                             withContext(Dispatchers.Main) {
+                                userInputEt.isEnabled = true
                                 userActionFab.isEnabled = true
                             }
                         }.collect { token ->
-                            val messageCount = messages.size
-                            check(messageCount > 0 && !messages[messageCount - 1].isUser)
-
-                            messages.removeAt(messageCount - 1).copy(
-                                content = lastAssistantMsg.append(token).toString()
-                            ).let { messages.add(it) }
-
                             withContext(Dispatchers.Main) {
+                                val messageCount = messages.size
+                                check(messageCount > 0 && !messages[messageCount - 1].isUser)
+
+                                messages.removeAt(messageCount - 1).copy(
+                                    content = lastAssistantMsg.append(token).toString()
+                                ).let { messages.add(it) }
+
                                 messageAdapter.notifyItemChanged(messages.size - 1)
                             }
                         }
@@ -195,6 +202,7 @@ class MainActivity : AppCompatActivity() {
     /**
      * Run a benchmark with the model file
      */
+    @Deprecated("This benchmark doesn't accurately indicate GUI performance expected by app developers")
     private suspend fun runBenchmark(modelName: String, modelFile: File) =
         withContext(Dispatchers.Default) {
             Log.i(TAG, "Starts benchmarking $modelName")
@@ -223,6 +231,16 @@ class MainActivity : AppCompatActivity() {
             if (!it.exists()) { it.mkdir() }
         }
 
+    override fun onStop() {
+        generationJob?.cancel()
+        super.onStop()
+    }
+
+    override fun onDestroy() {
+        engine.destroy()
+        super.onDestroy()
+    }
+
     companion object {
         private val TAG = MainActivity::class.java.simpleName
 

examples/llama.android/app/src/main/res/layout/activity_main.xml

@@ -24,7 +24,7 @@
                 android:id="@+id/gguf"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
-                android:layout_margin="16dp"
+                android:padding="16dp"
                 android:text="Selected GGUF model's metadata will show here."
                 style="@style/TextAppearance.MaterialComponents.Body2" />
 
@@ -33,8 +33,7 @@
         <com.google.android.material.divider.MaterialDivider
             android:layout_width="match_parent"
             android:layout_height="2dp"
-            android:layout_marginHorizontal="16dp"
-            android:layout_marginVertical="8dp" />
+            android:layout_marginHorizontal="16dp" />
 
         <androidx.recyclerview.widget.RecyclerView
             android:id="@+id/messages"