How would I implement a swipe-based circular control like this?

Question

I am working on an Android application, and I have a TextView where I display a price (for example 50$).

I would like to have a circular control similar to this picture:

Answer 1

The OvalSeekbar lib does something like that,I suggest you have a look at how the motion events are done in it.Here is the link to its git https://github.com/kshoji/AndroidCustomViews