Help with passing variables etc.

[Masterkirkby]

Hi there, I'm trying to pass a variable to a function from the OnCreate function and I get no errors, but it crashes no matter what I try passing. Here's where I'm using it:

and here's where I'm trying to pass it to:

I've tried setting a boolean flag and passing it and that doesn't work either. I've also tried declaring the flag as public static Boolean flag; in MainActivity and passing it as MainActivity.flag and it throws no errors, but it crashes everytime.

Any help would be great, thanks in advance!