I can't off code itself but i can offer the theory behind it with some pseudo code
First of all some theory:
Screens have a resolution this is mesured in pixels so for example, 1920*1080
on a screen of 10 inches, this is more pixels per inch so 20 pixels on this screen would take up less space then 20 pixels on a 40inch screen, because of this some math before the game starts is needed.
int width = getScreenWidth();
int height = getScreenHeight();
int dispWidth = getDeviceWidth();
int dispHeight = getDeviceWidth();
int PPI = caclulate the PPI with algorithm
You would then need to change some code to work out the pixels needed to fix say 1/2 inch diameter circle. which would be easy enough.
Another way to do it is looking on the Developer Documentation https://developer.android.com/reference/android/util/DisplayMetrics.html
it lists the size of the screens on different densities and then set variables according to that, It's been a few years since I've done any work with android but i believe you can also set pixel density on a canvas too.