通过鼠标事件绘制到NSView中

i am new to programming, objective-c (and stackoverflow). I'm learning and moving forward very slowly ;) but then I ran into a problem, which google couldn't solve. I have a single window and a NSview and then added a mouse event that should draw the coordinates into my view, but it doesn't. The funny thing is: it is drawn when the mouse moves over the window buttons of my apps window...i am new to programming, objective-c (and stack