requireActivity() and requireContext() in kotlin

Question

What is the purpose of requireActivity() and requireContext() in Fragment?

Answer 1

Because they might be null. In java you can just call for them. But in Kotlin they are declared as nullable return types. So you have 3 options:

1. You are not sure if it is null or not: activity?.let { //do what you need to do.}
2. You are sure it will not be null so you can call activity!!.doSomething but it is ugly.
3. This is the cleanest option where you are sure it will not be null, but if somehow it is, there will be a specific exception(IllegalStateException) prepared for this and it will be thrown and not generic NullPointerException.

Answer 2

Check the official Android Source code documentation. Those methods return activity/context with a null check.

requireActivity()

public final FragmentActivity requireActivity() {
        FragmentActivity activity = getActivity();
        if (activity == null) {
            throw new IllegalStateException("Fragment " + this + " not attached to an activity.");
        }
        return activity;
    }

requireContext()

public final Context requireContext() {
        Context context = getContext();
        if (context == null) {
            throw new IllegalStateException("Fragment " + this + " not attached to a context.");
        }
        return context;
    }