public class CustomScale extends View {
    static int screenSize = 480;
    static private float pxmm = screenSize / 67.f;
    int width, height, midScreenPoint;
    float startingPoint = 0;
    float downpoint = 0, movablePoint = 0, downPointClone = 0;
    private float mainPoint = 0, mainPointClone = 0;
    boolean isDown = false;
    boolean isUpward = false;
    private boolean isMove;
    private onViewUpdateListener mListener;
    private Paint rulerPaint, pinkPaint;
    private int endPoint;
    boolean isSizeChanged = false;
    float userStartingPoint = 0f;
    private int scaleLineMedium;
    private int scaleLineLarge;
    boolean isFirstTime = true;

    public CustomScale(Context context, AttributeSet foo) {
        super(context, foo);
        if (!isInEditMode()) {
            init(context);
        }
    }

    public interface onViewUpdateListener{
        void onViewUpdate(float result);
    }

    private void init(Context context) {
        rulerPaint = new Paint();
        rulerPaint.setStyle(Paint.Style.STROKE);
        rulerPaint.setStrokeWidth(2);
        rulerPaint.setAntiAlias(false);
        rulerPaint.setColor(Color.BLACK);
        pinkPaint = new Paint();
        pinkPaint.setStyle(Paint.Style.STROKE);
        pinkPaint.setStrokeWidth(4);
        pinkPaint.setAntiAlias(false);
        pinkPaint.setColor(ContextCompat.getColor(context , R.color.button_pink));
        scaleLineMedium = (int) getResources().getDimension(R.dimen.scale_line_medium);
        scaleLineLarge = (int) getResources().getDimension(R.dimen.scale_line_large);
    }

    public void setUpdateListener(onViewUpdateListener onViewUpdateListener) {
        mListener = onViewUpdateListener;
    }

    @Override
    public void onSizeChanged(int w, int h, int oldW, int oldH) {
        width = w;
        height = h;
        screenSize = height;
        pxmm = screenSize / 22.f;
        midScreenPoint = height / 2;
        endPoint = width - 40;
        if (isSizeChanged) {
            isSizeChanged = false;
            mainPoint = midScreenPoint - (userStartingPoint * 10 * pxmm);
        }
    }

    @Override
    public void onDraw(Canvas canvas) {

        startingPoint = mainPoint;
        for (int i = 5;; ++i) {
            if (startingPoint > screenSize) {
                break;
            }
            startingPoint = startingPoint + pxmm;
            int size = (i % 5 == 0) ? endPoint - scaleLineLarge : endPoint - scaleLineMedium ;
            canvas.drawLine(0, startingPoint, endPoint - size, startingPoint, rulerPaint);
        }
        canvas.drawLine(0, midScreenPoint, endPoint , midScreenPoint, pinkPaint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        System.out.println("touch event fire");
        mainPointClone = mainPoint;
        if (mainPoint < 0) {
            mainPointClone = -mainPoint;
        }
        float clickPoint = ((midScreenPoint + mainPointClone) / (pxmm * 10));
        if (mListener != null) {
            mListener.onViewUpdate((midScreenPoint + mainPointClone) / (pxmm * 10));
        }
        System.out.println("click point" + clickPoint + "");
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                isMove = true;
                isDown = false;
                isUpward = false;
                downpoint = event.getY();
                downPointClone = event.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                movablePoint = event.getY();
                if (downPointClone > movablePoint) {
/**
 * if user first starts moving downward and then upwards then
 * this method makes it to move upward
 */
                    if (isUpward) {
                        downpoint = event.getY();
                        downPointClone = downpoint;
                    }
                    isDown = true;
                    isUpward = false;
/**
 * make this differnce of 1, otherwise it moves very fast and
 * nothing shows clearly
 */
                    if (downPointClone - movablePoint > 1) {
                        mainPoint = mainPoint + (-(downPointClone - movablePoint));
                        downPointClone = movablePoint;
                        invalidate();
                    }
                } else {
// downwards
                    if (isMove) {
/**
 * if user first starts moving upward and then downwards,
 * then this method makes it to move upward
 */
                        if (isDown) {
                            downpoint = event.getY();
                            downPointClone = downpoint;
                        }
                        isDown = false;
                        isUpward = true;
                        if (movablePoint - downpoint > 1) {
                            mainPoint = mainPoint + ((movablePoint - downPointClone));
                            downPointClone = movablePoint;
                            if (mainPoint > 0) {
                                mainPoint = 0;
                                isMove = false;
                            }
                            invalidate();
                        }
                    }
                }
                break;
            case MotionEvent.ACTION_UP:
                System.out.println("up");
            default:
                break;
        }
        return true;
    }

    public void setStartingPoint(float point) {
        userStartingPoint = point;
        isSizeChanged = true;
        if (isFirstTime) {
            isFirstTime = false;
            if (mListener != null) {
                mListener.onViewUpdate(point);
            }
        }
    }
}