@Override
    protected Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        CustomState state = new CustomState(superState);
        state.progress = getProgress();
        state.max = mMax;
        state.min = mMin;
        return state;
    }
When the {@link DiscreteSeekBar} value changes this method is called
<p>
Subclasses may override this to add functionality around this event
without having to specify a {@link OnProgressChangeListener}
</p>
app/src/main/java/com/duan/musicoco/view/discreteseekbar/DiscreteSeekBar.java