Android Service implementation with fullscreen overlay window (over status bar & navigation bar)

FullscreenOverlayService.java

class FullscreenOverlayService extends Service {

    private View overlay;
    private WindowManager windowManager;

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);

        overlay = View.inflate(getApplicationContext(), R.layout.overlay_service, null);
        overlay.findViewById(R.id.button_stop).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopSelf();
            }
        });

        WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
                        WindowManager.LayoutParams.FLAG_FULLSCREEN |
                        WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN |
                        WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS |
                        WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR |
                        WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
                PixelFormat.TRANSLUCENT
        );
        layoutParams.gravity = Gravity.LEFT | Gravity.TOP;
        windowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
        windowManager.addView(overlay, layoutParams);

        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        windowManager.removeView(overlay);
    }
}


class FullscreenOverlayLayout extends FrameLayout {

    // コンストラクタ...

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        WindowManager windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        Point screenSize = new Point();
        windowManager.getDefaultDisplay().getRealSize(screenSize);

        super.onMeasure(
                MeasureSpec.makeMeasureSpec(screenSize.x, MeasureSpec.getMode(widthMeasureSpec)),
                MeasureSpec.makeMeasureSpec(screenSize.y, MeasureSpec.getMode(heightMeasureSpec))
        );
    }
}

class OverlayDrawingView extends View {

    // コンストラクタ...

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        // カスタム描画処理...
    }
}

FullscreenOverlayService.kt

class FullscreenOverlayService : Service() {

    private val overlay by lazy {
        View.inflate(applicationContext, R.layout.overlay_service, null).also {
            it.button_stop.setOnClickListener {
                stopSelf()
            }
        }
    }

    private val windowManager by lazy {
        applicationContext.getSystemService(Context.WINDOW_SERVICE) as WindowManager
    }

    override fun onBind(intent: Intent?): IBinder? {
        return null
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        super.onStartCommand(intent, flags, startId)

        val layoutParams = WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or
                        WindowManager.LayoutParams.FLAG_FULLSCREEN or
                        WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN or
                        WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS or
                        WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR or
                        WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
                PixelFormat.TRANSLUCENT
        ).also {
            it.gravity = Gravity.LEFT or Gravity.TOP
        }
        windowManager.addView(overlay, layoutParams)

        return START_STICKY
    }

    override fun onDestroy() {
        super.onDestroy()
        windowManager.removeView(overlay)
    }
}

class FullscreenOverlayLayout @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = 0
) : FrameLayout(context, attrs, defStyleAttr) {

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        val windowManager = context.getSystemService(Context.WINDOW_SERVICE) as WindowManager
        val screenSize = Point().also { windowManager.defaultDisplay.getRealSize(it) }

        super.onMeasure(
                MeasureSpec.makeMeasureSpec(screenSize.x, MeasureSpec.getMode(widthMeasureSpec)),
                MeasureSpec.makeMeasureSpec(screenSize.y, MeasureSpec.getMode(heightMeasureSpec))
        )
    }
}

class OverlayDrawingView @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {

    private val paint by lazy {
        Paint().apply {
            color = Color.LTGRAY
            style = Paint.Style.STROKE
            strokeWidth = 8f
        }
    }

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)

        if (canvas != null && canvas.width > 0) {
            val W = canvas.width
            val H = canvas.height
            val interval = W / STEP

            // 斜めパターンの描画
            generateSequence(0f) { it + interval }
                    .take(STEP + H / interval + 1)
                    .forEach { canvas.drawLine(it, 0f, 0f, it, paint) }

            canvas.drawRect(0f, 0f, W.toFloat(), H.toFloat(), paint)
        }
    }

    companion object {
        private const val STEP = 9
    }
}

overlay_service.xml

<?xml version="1.0" encoding="utf-8"?>
<com.labo.kaji.playground.FullscreenOverlayLayout
    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"
    >

    <com.labo.kaji.playground.OverlayDrawingView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_gravity="center"
        >

        <TextView
            android:id="@+id/text_hello"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello Overlay!"
            android:textSize="16sp"
            android:textColor="#FFF"
            />

        <Button
            android:id="@+id/button_stop"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="Stop"
            />

    </LinearLayout>

</com.labo.kaji.playground.FullscreenOverlayLayout>