Smart Home Android Client

This is the native Android client for the custom Smart Home control system. It acts as a remote control, communicating with the C++ backend server via a secured REST API to manage IoT devices in real-time.

1. Architecture

The application follows a clean client-server model tailored for Android:

1. UI Layer (Frontend): XML layouts define the user interface, providing intuitive controls (Buttons, TextViews, EditTexts) for each device type.
2. Business Logic (Activity): MainActivity handles user interactions, validates input (e.g., temperature limits), and manages the application lifecycle.
3. Network Layer (Data): Powered by Retrofit 2, this layer handles all HTTP communication. It uses Kotlin Coroutines for asynchronous non-blocking calls and automatically injects the required X-API-Key security token into every request.

2. Features

• Real-time Control: Instantly toggle lights, lock/unlock doors, and adjust air conditioner temperature.
• Live Status Updates: The app fetches and displays the current state of all devices directly from the server upon launch and after every action.
• Secure Communication: All API requests are authenticated using a custom X-API-Key header.
• Input Validation: Prevents sending invalid data (e.g., temperature outside the 13-31°C range) to the server.

3. Tech Stack

• Language: Kotlin
• Core Components: Android SDK, AppCompat
• Networking: Retrofit 2, OkHttp, GSON (for JSON parsing)
• Concurrency: Kotlin Coroutines (suspend functions, lifecycleScope)
• Build System: Gradle

4. Setup & Configuration

Before building the project, you must configure it to match your local network environment.

Prerequisites

• Android Studio Iguana (or newer)
• Android SDK (API level 31 or higher recommended)
• An Android device or emulator connected to the same Wi-Fi network as the C++ server.

Configuration Steps

1. Configure Server IP: Open app/src/main/java/com/example/smarthomeapp/RetrofitClient.kt and update the BASE_URL with your C++ server's local IP address:

   // Replace '192.168.0.104' with your actual server IP found via 'ipconfig'
   private const val BASE_URL = "[http://192.168.0.104:18080/](http://192.168.0.104:18080/)"

2. Configure Security Token: Open app/src/main/java/com/example/smarthomeapp/MainActivity.kt and ensure the API_KEY matches the one configured on your backend:

   private val API_KEY = "my-secret-key-12345"

3. Network Permissions: Ensure your AndroidManifest.xml includes the necessary permissions for local network communication:

   <uses-permission android:name="android.permission.INTERNET" />
   <application
       ...
       android:usesCleartextTraffic="true"
       ...>

5. Building and Running

1. Open Project: Launch Android Studio and open the project root folder.
2. Sync Gradle: Allow Android Studio to download necessary dependencies.
3. Run: Connect your Android device via USB (ensure USB Debugging is enabled) or launch an AVD (Android Virtual Device). Click the Run button (▶) in Android Studio.

6. Troubleshooting

• "Network Error" / Timeout:
  • Ensure both phone and PC are on the same Wi-Fi network.
  • Verify the IP address in RetrofitClient.kt matches your PC's current IP.
  • Check Windows Firewall on your PC — allow incoming traffic on port 18080 for Private networks.
• "Cleartext traffic not permitted":
  • Android blocks unencrypted HTTP by default. Verify that android:usesCleartextTraffic="true" is present in your AndroidManifest.xml tag.
• 401 Unauthorized:
  • The API_KEY in MainActivity.kt does not match the key expected by the C++ server.