Android - Which Button was pressed first? : I need a way to know which of my buttons was pressed first. The app layout is more or less like this.:

Button1   Button2   
Button3   Button4   
Button5   Button6   
Button7   Button8   
Button9   Button10   
Button11   Button12

And if one of the buttons of it's "line" is pressed, the other disappears. The thing is, I have no idea how to know which one of all these 12 buttons was pressed first, then pressed second, then pressed third and so on...

The code I have for hiding buttons works well, but that's pretty much the easy part.

    button1.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View arg0) {
    
                            button1.setVisibility(View.GONE);
                            button2.setVisibility(View.GONE);
    
                        }
                    });

I searched but maybe I don't know what exactly to search for, and I didn't find a good answer. 
Thanks in advance!