setContentView(R.layout.activity_main);
change this to
setContentView(new board(this));
Since you are not creating a new instance of the class board
and setting as the content, this view wont get added. It is conventional to start a class name with capital letter.
Add this inside the onDraw
for
loop instead of drawing the bitmap.
canvas.drawCircle(50, (x + 1) * 2 * 50, (y + 1) * 2 * 50, black);