public void setCircleFillRatio(float fillRatio) {
        pieChartRenderer.setCircleFillRatio(fillRatio);
        ViewCompat.postInvalidateOnAnimation(this);
    }
Set how much of view area should be taken by chart circle. Value should be between 0 and 1. Default is 1 so
circle will have radius equals min(View.width, View.height).
hellocharts-library/src/lecho/lib/hellocharts/view/PieChartView.java