Here you are.
I converted your project into a B4XPages project. It is much easier to develop cross-platform projects.
Modifications:
1. I changed the Ball view from a Label into a B4XView (Panel) to be able to draw onto it.
You used a Label and Reflection to draw onto it which is B4A specific.
The Ball view has a fixed size.
2. I replaced the routine MyCorned by new InitBall routine which draws the marker.
It is an oval with a triangle, does not look too bad. Yours was more sophisticated with quadratic curves.
What i found 'strange' is that you defined a square view with 80dip x 80dip and display it afterwards with a size of 50dip x 55dip.
I set it directly to 35dip x 50dip which looks almost like yours, but a fixed size.
3. I removed the firsttrack view, which represents the background line, and draw this line directly onto the Panel in setValue.
4. I removed the thumb view (the circle) and draw the circle directly with the front line in setValue.
This implies that I draw the lines not from the beginning of the Panel til its end, but with an offset which is the circle radius, maybe you could set it to the half of the height.
5. In the setValue routine, i removed the second parameter Click, it is not used.
You used setValue and getValue the wrong way. Routines with lower-case set and get prefixes are supposed to be property routines and the setValue should have only one parameter, you had two. If you really want the Click parameter you need to change it.
6. I removed all original not used code and left only the new. I found that keeping all the code used and the commented not used code more difficult to read.
It is easy to compare having both projects side by side.
As the Ball view is added onto the parent view of the BubbleSlider, be aware that depending on the parent view the Ball might not be displayed or only partly.
To see this, move the BubbleSlider, in the Designer, to almost on top and you see that the Ball will be outsides the visible part.
Well, i played a bit more with your project and did not just answer your question in the first post.
Screenshot:
View attachment 138675
Attached the B4XPages project.
Tested with B4A and B4J. Unfortunately, i have not tested it with B4i, i have currently problems with it.
EDIT: New version, also tested with B4i in the next post.