App crashing when change of screens

Here’s a link for my project. What’s wrong with it?

I press button “login” at start in loginscreen, then I come to mainscreen and when I try to open(click button) another screen it crashes :thinking: Any idea why?

I use Galaxy S7

I see the app has been shared 2 times, any suggestions on what’s wrong? Is it a bug or anything I’ve done wrong?