When I change orientation portrait to landscap, a function is restarted in android. How can I resove it? :  
[![When I change orientation portrait to landscape(or landscaper to portrait), a function is restarted. I want the function is saved in android. I'm making a calculator. I don't want operator buttons to be enable before number buttons is clicked. So I made a function that make operator buttons click after number buttons is clicked. However, when I clicked a number to calculate, then change orientation, the operator buttons are not enable. It's supposed to be enable. 
I mean, number click -> operator click -> number click -> equals button click -> the result is showed, this is okay. But number click -> change orientation -> operator buttons are not enable.... This is my code ↓][1]]


  [1]: http://i.stack.imgur.com/UR76S.png