@Override
    public void setAlpha(int alpha) {
        mAlpha = alpha;
        updateCurColor();
        invalidateSelf();
    }
A drawable that changes it's Paint and color depending on the Drawable State
For SeekBarDrawable {@link SeekBarDrawable}

@Hide
caprice/ui/src/main/java/net/qiujuer/genius/ui/drawable/SeekBarStateDrawable.java