private void prepareDataAnimation() {
            for (SliceValue value : data.getValues()) {
                value.setTarget((float) Math.random() * 30 + 15);
            }
        }
To animate values you have to change targets values and then call {@link Chart#startDataAnimation()}
method(don't confuse with View.animate()).
hellocharts-samples/src/lecho/lib/hellocharts/samples/PieChartActivity.java