How to restrict outer screen when a alert box is popped up in android

I have my alert box created in different folder since i access it in several places in my project i made it like that and invoke it when needed.

Now my problem is when i check a checkbox i get the alertbox pop up when i touch outer screen other than yes or no in the alert the alert box is getting closed and my checkbox is remaining checked. I have to restrict the outer screen how can i do this.

I know i can use checkbox.setCanceledOnTouchOutside(false) method but i am confused where to place it.