@Override
    protected synchronized void onDraw(Canvas canvas) {
        canvas.rotate(-90);
        canvas.translate(-getHeight(), 0);

        super.onDraw(canvas);
        String progressText = String.valueOf(getProgress());
        Rect bounds = new Rect();
        mTextPaint.getTextBounds(progressText, 0, progressText.length(), bounds);

        int leftPadding = getPaddingLeft() - getThumbOffset();
        int rightPadding = getPaddingRight() - getThumbOffset();
        int width = getWidth() - leftPadding - rightPadding;
        float progressRatio = (float) getProgress() / getMax();
        float thumbOffset = mThumbSize * (.5f - progressRatio);
        float thumbX = progressRatio * width + leftPadding + thumbOffset;
        float thumbY = getHeight() / 2f + bounds.height() / 2f;
        canvas.drawText(progressText, thumbX, thumbY, mTextPaint);
        canvas.rotate(90);
    }