Android: How to detect collision between two circles

Question

I have drawn multiple circles of varying sizes and positions to a canvas, but I need to detect collisions between them.

public void run() {         
            while(Run){
                if(!sHold.getSurface().isValid())
                    continue;

                c[0][cnum].r++;
                canvas = sHold.lockCanvas();
                canvas.drawRGB(02, 02, 150);
                Paint white = new Paint();
                white.setColor(Color.WHITE);
                if(c[0][cnum].x != 0 && c[0][cnum].y != 0)
                    canvas.drawCircle(c[0][cnum].x, c[0][cnum].y, c[0][cnum].r, white);
                if(cnum!=0)
                    for(int i=0; i<cnum; i++)
                        canvas.drawCircle(c[1][i].x, c[1][i].y, c[1][i].r, white);
                sHold.unlockCanvasAndPost(canvas);
                if(((c[0][cnum].x - c[0][cnum].r)<0)||((c[0][cnum].y-c[0][cnum].r)<0)||((c[0][cnum].y+c[0][cnum].r)>height)||((c[0][cnum].x+c[0][cnum].r>width))){
                    c[1][cnum].x = c[0][cnum].x;
                    c[1][cnum].y = c[0][cnum].y;
                    c[1][cnum].r = c[0][cnum].r;
                    broken = true;
                    break;
                }
            }
        }

Answer 1

You shouldn't do that on render phases.

When processing the logics you should check if circles intersects as described:

v1 = center of circle1 v2 = center of circle2

intersects = v1 - v2 < circle1radius + circle2radius