Add in-app chat with streaming, settings UI, and request indicator

Chat:
- ChatActivity with RecyclerView message list (user/AI bubbles)
- Streams tokens directly from LiteRT model via generateStreaming()
- Maintains full conversation history (multi-turn context)
- Respects auto_system_prompt setting from SharedPreferences
- "Chat" button in MainActivity, enabled only when server is running
- "⚡ Generating…" indicator while model is thinking
- Log on main screen unchanged — still shows all requests

Server:
- Settings card: temperature slider, max tokens, system prompt toggle
- "⚡ Processing request…" indicator in status card during inference
- onActiveRequest callback wired through service → activity

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -27,6 +27,11 @@
         android:networkSecurityConfig="@xml/network_security_config"
         android:theme="@style/Theme.Pixel10AI">
 
+        <activity
+            android:name=".ui.ChatActivity"
+            android:exported="false"
+            android:windowSoftInputMode="adjustResize" />
+
         <activity
             android:name=".ui.MainActivity"
             android:exported="true"

app/src/main/java/com/pixel10/ai/server/ApiServerService.kt

@@ -38,6 +38,7 @@ class ApiServerService : Service() {
 
     val isRunning: Boolean get() = server != null
     val requestCount: Long get() = server?.requestCount?.get() ?: 0
+    val currentModel: OnDeviceModel? get() = model
 
     inner class LocalBinder : Binder() {
         val service: ApiServerService get() = this@ApiServerService

app/src/main/java/com/pixel10/ai/ui/ChatActivity.kt

@@ -0,0 +1,158 @@
+package com.pixel10.ai.ui
+
+import android.content.ComponentName
+import android.content.Context
+import android.content.Intent
+import android.content.ServiceConnection
+import android.os.Bundle
+import android.os.IBinder
+import android.view.View
+import android.view.inputmethod.EditorInfo
+import androidx.appcompat.app.AppCompatActivity
+import androidx.lifecycle.lifecycleScope
+import androidx.recyclerview.widget.LinearLayoutManager
+import com.pixel10.ai.databinding.ActivityChatBinding
+import com.pixel10.ai.inference.OnDeviceModel
+import com.pixel10.ai.server.AgentConfig
+import com.pixel10.ai.server.ApiServerService
+import kotlinx.coroutines.launch
+
+class ChatActivity : AppCompatActivity() {
+
+    private lateinit var binding: ActivityChatBinding
+    private val messages = mutableListOf<ChatMessage>()
+    private lateinit var adapter: MessageAdapter
+    private var service: ApiServerService? = null
+    private var bound = false
+    private var generating = false
+
+    private val serviceConnection = object : ServiceConnection {
+        override fun onServiceConnected(name: ComponentName?, binder: IBinder?) {
+            service = (binder as ApiServerService.LocalBinder).service
+            bound = true
+        }
+        override fun onServiceDisconnected(name: ComponentName?) {
+            service = null
+            bound = false
+        }
+    }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        binding = ActivityChatBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+
+        setSupportActionBar(binding.toolbar)
+        binding.toolbar.setNavigationOnClickListener { finish() }
+
+        adapter = MessageAdapter(messages)
+        binding.rvMessages.layoutManager = LinearLayoutManager(this).also {
+            it.stackFromEnd = true
+        }
+        binding.rvMessages.adapter = adapter
+
+        binding.btnSend.setOnClickListener { sendMessage() }
+        binding.etMessage.setOnEditorActionListener { _, actionId, _ ->
+            if (actionId == EditorInfo.IME_ACTION_SEND) { sendMessage(); true } else false
+        }
+    }
+
+    override fun onStart() {
+        super.onStart()
+        bindService(
+            Intent(this, ApiServerService::class.java),
+            serviceConnection,
+            Context.BIND_AUTO_CREATE
+        )
+    }
+
+    override fun onStop() {
+        super.onStop()
+        if (bound) { unbindService(serviceConnection); bound = false }
+    }
+
+    private fun sendMessage() {
+        if (generating) return
+        val text = binding.etMessage.text.toString().trim()
+        if (text.isEmpty()) return
+
+        binding.etMessage.text?.clear()
+
+        // Add user message
+        messages.add(ChatMessage("user", text))
+        adapter.notifyItemInserted(messages.size - 1)
+        scrollToBottom()
+
+        // Add empty AI placeholder
+        messages.add(ChatMessage("assistant", ""))
+        val aiIndex = messages.size - 1
+        adapter.notifyItemInserted(aiIndex)
+        scrollToBottom()
+
+        binding.tvTyping.visibility = View.VISIBLE
+        binding.btnSend.isEnabled = false
+        generating = true
+
+        val model = service?.currentModel
+        if (model == null || !model.isReady) {
+            messages[aiIndex].content = "⚠️ Server not running — start the server first."
+            adapter.notifyItemChanged(aiIndex)
+            finishGeneration()
+            return
+        }
+
+        val prompt = buildPrompt()
+
+        lifecycleScope.launch {
+            try {
+                model.generateStreaming(prompt) { token ->
+                    runOnUiThread {
+                        messages[aiIndex].content += token
+                        adapter.notifyItemChanged(aiIndex)
+                        scrollToBottom()
+                    }
+                }
+            } catch (e: Exception) {
+                runOnUiThread {
+                    messages[aiIndex].content = "⚠️ Error: ${e.message}"
+                    adapter.notifyItemChanged(aiIndex)
+                }
+            } finally {
+                runOnUiThread { finishGeneration() }
+            }
+        }
+    }
+
+    private fun finishGeneration() {
+        generating = false
+        binding.tvTyping.visibility = View.GONE
+        binding.btnSend.isEnabled = true
+        scrollToBottom()
+    }
+
+    private fun buildPrompt(): String {
+        val prefs = getSharedPreferences("pixel10_prefs", MODE_PRIVATE)
+        val useSystemPrompt = prefs.getBoolean("auto_system_prompt", true)
+
+        val sb = StringBuilder()
+        if (useSystemPrompt) {
+            sb.append("System: ${AgentConfig.SYSTEM_PROMPT}\n\n")
+        }
+        // Include all messages except the last empty AI placeholder
+        for (i in 0 until messages.size - 1) {
+            val msg = messages[i]
+            when (msg.role) {
+                "user"      -> sb.append("User: ${msg.content}\n\n")
+                "assistant" -> sb.append("Assistant: ${msg.content}\n\n")
+            }
+        }
+        sb.append("Assistant:")
+        return sb.toString()
+    }
+
+    private fun scrollToBottom() {
+        if (messages.isNotEmpty()) {
+            binding.rvMessages.smoothScrollToPosition(messages.size - 1)
+        }
+    }
+}

app/src/main/java/com/pixel10/ai/ui/ChatMessage.kt

@@ -0,0 +1,3 @@
+package com.pixel10.ai.ui
+
+data class ChatMessage(val role: String, var content: String)

app/src/main/java/com/pixel10/ai/ui/MainActivity.kt

@@ -104,6 +104,10 @@ class MainActivity : AppCompatActivity() {
             if (service?.isRunning == true) stopServer() else startServer()
         }
 
+        binding.btnChat.setOnClickListener {
+            startActivity(Intent(this, ChatActivity::class.java))
+        }
+
         binding.btnDownloadModel.setOnClickListener {
             saveHfToken()
             startModelDownload(ModelSpec.GEMMA_3N_E4B)
@@ -272,6 +276,7 @@ class MainActivity : AppCompatActivity() {
                 binding.tvModelStatus.text = "Model: not loaded"
                 binding.btnToggle.text = getString(R.string.btn_start)
                 binding.btnToggle.isEnabled = true
+                binding.btnChat.isEnabled = false
             }
             ApiServerService.ServerState.LOADING_MODEL -> {
                 binding.tvServerStatus.text = getString(R.string.server_status_starting)
@@ -288,6 +293,7 @@ class MainActivity : AppCompatActivity() {
                 binding.tvModelStatus.text = getString(R.string.model_ready)
                 binding.btnToggle.text = getString(R.string.btn_stop)
                 binding.btnToggle.isEnabled = true
+                binding.btnChat.isEnabled = true
             }
             ApiServerService.ServerState.ERROR -> {
                 binding.tvServerStatus.text = getString(R.string.server_status_error)

app/src/main/java/com/pixel10/ai/ui/MessageAdapter.kt

@@ -0,0 +1,43 @@
+package com.pixel10.ai.ui
+
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.recyclerview.widget.RecyclerView
+import com.pixel10.ai.R
+
+class MessageAdapter(private val messages: List<ChatMessage>) :
+    RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+
+    companion object {
+        private const val TYPE_USER = 0
+        private const val TYPE_AI = 1
+    }
+
+    override fun getItemViewType(position: Int) =
+        if (messages[position].role == "user") TYPE_USER else TYPE_AI
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
+        val inflater = LayoutInflater.from(parent.context)
+        return if (viewType == TYPE_USER) {
+            val view = inflater.inflate(R.layout.item_message_user, parent, false)
+            UserViewHolder(view.findViewById(R.id.tvContent))
+        } else {
+            val view = inflater.inflate(R.layout.item_message_ai, parent, false)
+            AiViewHolder(view.findViewById(R.id.tvContent))
+        }
+    }
+
+    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
+        val msg = messages[position]
+        when (holder) {
+            is UserViewHolder -> holder.tv.text = msg.content
+            is AiViewHolder  -> holder.tv.text = msg.content.ifEmpty { "▌" }
+        }
+    }
+
+    override fun getItemCount() = messages.size
+
+    class UserViewHolder(val tv: TextView) : RecyclerView.ViewHolder(tv.parent as android.view.View)
+    class AiViewHolder(val tv: TextView)  : RecyclerView.ViewHolder(tv.parent as android.view.View)
+}

app/src/main/res/drawable/bubble_ai.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <solid android:color="@color/surface_variant" />
+    <corners
+        android:topLeftRadius="4dp"
+        android:topRightRadius="16dp"
+        android:bottomLeftRadius="16dp"
+        android:bottomRightRadius="16dp" />
+</shape>

app/src/main/res/drawable/bubble_user.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <solid android:color="@color/primary" />
+    <corners
+        android:topLeftRadius="16dp"
+        android:topRightRadius="16dp"
+        android:bottomLeftRadius="16dp"
+        android:bottomRightRadius="4dp" />
+</shape>

app/src/main/res/drawable/ic_back.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="@color/on_surface">
+    <path
+        android:fillColor="@color/on_surface"
+        android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z" />
+</vector>

app/src/main/res/layout/activity_chat.xml

@@ -0,0 +1,76 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:background="@color/surface">
+
+    <!-- Toolbar -->
+    <androidx.appcompat.widget.Toolbar
+        android:id="@+id/toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="?attr/actionBarSize"
+        android:background="@color/surface_variant"
+        android:paddingStart="4dp"
+        app:title="Chat"
+        app:titleTextColor="@color/on_surface"
+        app:navigationIcon="@drawable/ic_back" />
+
+    <!-- Message list -->
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rvMessages"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_weight="1"
+        android:padding="12dp"
+        android:clipToPadding="false" />
+
+    <!-- Typing indicator -->
+    <TextView
+        android:id="@+id/tvTyping"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingStart="16dp"
+        android:paddingEnd="16dp"
+        android:paddingBottom="4dp"
+        android:text="⚡ Generating…"
+        android:textColor="@color/primary"
+        android:textSize="12sp"
+        android:visibility="gone" />
+
+    <!-- Input row -->
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:gravity="center_vertical"
+        android:padding="8dp"
+        android:background="@color/surface_variant">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:id="@+id/etMessage"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:hint="Message…"
+            android:textColor="@color/on_surface"
+            android:textColorHint="@color/log_text"
+            android:textSize="15sp"
+            android:maxLines="4"
+            android:inputType="textMultiLine|textCapSentences"
+            android:backgroundTint="@color/primary" />
+
+        <com.google.android.material.button.MaterialButton
+            android:id="@+id/btnSend"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="8dp"
+            android:text="Send"
+            android:textSize="14sp"
+            app:cornerRadius="8dp" />
+
+    </LinearLayout>
+
+</LinearLayout>

app/src/main/res/layout/activity_main.xml

@@ -324,18 +324,38 @@
         </LinearLayout>
     </com.google.android.material.card.MaterialCardView>
 
-    <!-- Start/Stop Button -->
-    <com.google.android.material.button.MaterialButton
-        android:id="@+id/btnToggle"
+    <!-- Start/Stop + Chat Buttons -->
+    <LinearLayout
+        android:id="@+id/layoutButtons"
         android:layout_width="0dp"
-        android:layout_height="56dp"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
         android:layout_marginTop="16dp"
-        android:text="@string/btn_start"
-        android:textSize="16sp"
-        app:cornerRadius="12dp"
         app:layout_constraintTop_toBottomOf="@id/layoutPort"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintEnd_toEndOf="parent" />
+        app:layout_constraintEnd_toEndOf="parent">
+
+        <com.google.android.material.button.MaterialButton
+            android:id="@+id/btnToggle"
+            android:layout_width="0dp"
+            android:layout_height="56dp"
+            android:layout_weight="1"
+            android:text="@string/btn_start"
+            android:textSize="16sp"
+            app:cornerRadius="12dp" />
+
+        <com.google.android.material.button.MaterialButton
+            android:id="@+id/btnChat"
+            style="@style/Widget.MaterialComponents.Button.OutlinedButton"
+            android:layout_width="wrap_content"
+            android:layout_height="56dp"
+            android:layout_marginStart="8dp"
+            android:text="Chat"
+            android:textSize="16sp"
+            android:enabled="false"
+            app:cornerRadius="12dp" />
+
+    </LinearLayout>
 
     <!-- Log Output -->
     <TextView
@@ -347,7 +367,7 @@
         android:textSize="14sp"
         android:textStyle="bold"
         android:layout_marginTop="20dp"
-        app:layout_constraintTop_toBottomOf="@id/btnToggle"
+        app:layout_constraintTop_toBottomOf="@id/layoutButtons"
         app:layout_constraintStart_toStartOf="parent" />
 
     <ScrollView
@@ -358,6 +378,7 @@
         android:background="@color/log_bg"
         android:padding="12dp"
         app:layout_constraintTop_toBottomOf="@id/tvLogLabel"
+
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintEnd_toEndOf="parent">

app/src/main/res/layout/item_message_ai.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="horizontal"
+    android:gravity="start"
+    android:paddingTop="4dp"
+    android:paddingBottom="4dp">
+
+    <TextView
+        android:id="@+id/tvContent"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:maxWidth="280dp"
+        android:background="@drawable/bubble_ai"
+        android:padding="10dp"
+        android:textColor="@color/on_surface"
+        android:textSize="14sp"
+        android:lineSpacingMultiplier="1.2"
+        android:fontFamily="monospace" />
+
+</LinearLayout>

app/src/main/res/layout/item_message_user.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="horizontal"
+    android:gravity="end"
+    android:paddingTop="4dp"
+    android:paddingBottom="4dp">
+
+    <TextView
+        android:id="@+id/tvContent"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:maxWidth="280dp"
+        android:background="@drawable/bubble_user"
+        android:padding="10dp"
+        android:textColor="#FFFFFF"
+        android:textSize="14sp"
+        android:lineSpacingMultiplier="1.2" />
+
+</LinearLayout>