Stage 1. I have a background

Stage 2. I apply an overlay to background with a canvas to draw. First I fill the whole area with canvas.drawColor(Color.argb(128,0,0,0))

Then I need to draw a red transparent circle with color.argb(128,255,0,0) at a specified place, but I want circle red transparency replaced black filling transparency, not added. So, I wanna get this

but NOT this

How can I get it?
You can try to use Canvas.clipPath before filling area with black color to exclude area, which will be used later by circle.