@Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        //HACK: Sometimes, the animateOpen() call is made before the View is attached
        //so the drawable cannot schedule itself to run the animation
        //I think we can call it here safely.
        //I've seen it happen in android 2.3.7
        animateOpen();
    }
{@link ViewGroup} to be used as the real indicator.
<p>
I've used this to be able to accommodate the TextView
with the required positions and offsets
</p>

@hide
app/src/main/java/com/duan/musicoco/view/discreteseekbar/internal/Marker.java