NullPointerException

[ghost]

in RVAdapter,

public static ElegantNumberButton button;

in MainActivity,

SubMenuRVAdapter.button.setNumber("0");

When I click Send button, I want to set ElegantNumberButton number "0" as a default. This ElegantNumberButton, findViewById come from RVAdapter.

[ashik94vc]

The problem for you is in SubMenuRVAdapter. I don't exactly know what's happening unless I can see the Log or at least your code for SubMenuRv Adapter where you're calling ElegantNumberButton. I'd also advice you to not make the button as static. This doesn't initialize the object.