问如何在Android中创建快速或慢速相机闪光灯闪烁信号？

EN

    public class FlashBlinkService extends Service 
    {
        private static Camera cam = null;
        private Handler handler = new Handler();

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

        @Override
        public void onCreate()
        {
            super.onCreate();
            startFlashBlink();      
        }

        //for simulating flash blink
        Runnable flashBlinkRunnable = new Runnable()
        {
            public void run() 
            {   
                cam = Camera.open();
                Parameters p = cam.getParameters();
                p.setFlashMode(Parameters.FLASH_MODE_TORCH);
                cam.setParameters(p);
                cam.startPreview();
                p.setFlashMode(Parameters.FLASH_MODE_OFF);
                cam.setParameters(p);
                cam.stopPreview();
                cam.release();
                cam = null;
                //--->
                handler.post(flashBlinkRunnable);
            }       
        };

        //start flash blink light
        public void startFlashBlink()
        {
            flashBlinkRunnable.run();
        }

        //stop flash blink light
        public void stopFlashBlink()
        {
            handler.removeCallbacks(flashBlinkRunnable);
            stopCamera(cam);
        }

        //stop camera
        private void stopCamera(Camera cam)
        {
            if (cam != null)
            {
                cam.stopPreview();
                cam.release();
                cam = null;
            }
        }

        @Override
        public void onDestroy()
        {
            super.onDestroy();
            handler.removeCallbacks(flashBlinkRunnable);
            stopCamera(cam);
        }
    }