📱 Android Development Skill

Use Cases

• Screen mirroring (MediaProjection)
• Remote control (Accessibility Service)
• Real-time communication (Socket.IO)
• Background services

---

MediaProjection Setup

1. Request Permission

val mediaProjectionManager = getSystemService(MEDIA_PROJECTION_SERVICE) as MediaProjectionManager
startActivityForResult(mediaProjectionManager.createScreenCaptureIntent(), REQUEST_CODE)

2. Create Projection

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
        mediaProjection = mediaProjectionManager.getMediaProjection(resultCode, data!!)
        startCapture()
    }
}

3. ImageReader for Frames

val imageReader = ImageReader.newInstance(width, height, PixelFormat.RGBA_8888, 5)
imageReader.setOnImageAvailableListener({ reader ->
    val image = reader.acquireLatestImage()
    // Process frame...
    image?.close()
}, handler)

---

Foreground Service (Android 14+)

⚠️ CRITICAL: Must call startForeground() immediately in onStartCommand()

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    // FIRST: Start foreground immediately!
    val notification = createNotification()
    startForeground(NOTIFICATION_ID, notification, ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PROJECTION)
    
    // THEN: Extract intent and start work
    val resultCode = intent?.getIntExtra("resultCode", -1) ?: -1
    val data = intent?.getParcelableExtra("data", Intent::class.java)
    
    // Add delay before capture
    Handler(Looper.getMainLooper()).postDelayed({
        startCapture(resultCode, data)
    }, 1500)
    
    return START_NOT_STICKY
}

---

Socket.IO Connection

val socket = IO.socket("http://192.168.1.x:3000")

socket.on(Socket.EVENT_CONNECT) {
    Log.d("Socket", "Connected!")
    socket.emit("register", deviceInfo)
}

socket.on("command") { args ->
    val command = args[0] as JSONObject
    handleCommand(command)
}

socket.connect()

---

Accessibility Service

class RemoteControlService : AccessibilityService() {
    
    override fun onAccessibilityEvent(event: AccessibilityEvent?) {
        // Handle accessibility events
    }
    
    fun performClick(x: Int, y: Int) {
        val path = Path().apply { moveTo(x.toFloat(), y.toFloat()) }
        val gesture = GestureDescription.Builder()
            .addStroke(GestureDescription.StrokeDescription(path, 0, 100))
            .build()
        dispatchGesture(gesture, null, null)
    }
    
    fun performSwipe(startX: Int, startY: Int, endX: Int, endY: Int) {
        val path = Path().apply {
            moveTo(startX.toFloat(), startY.toFloat())
            lineTo(endX.toFloat(), endY.toFloat())
        }
        val gesture = GestureDescription.Builder()
            .addStroke(GestureDescription.StrokeDescription(path, 0, 300))
            .build()
        dispatchGesture(gesture, null, null)
    }
}

---

Decision Tree

Android task?
├── Screen capture? → MediaProjection + ImageReader
├── Background work? → Foreground Service (Android 14 rules!)
├── Remote control? → Accessibility Service
├── Network comm? → Socket.IO
└── Permissions? → Runtime request + Manifest

---

Common Pitfalls

ปัญหา	สาเหตุ	แก้ไข
Black screen	startForeground timing	Call immediately in onStartCommand
Crash on Android 14	Wrong intent extraction	Use getParcelableExtra(key, Class)
Low FPS	Buffer too small	Increase ImageReader buffer to 5
Service killed	Not foreground	Add FOREGROUND_SERVICE permission