getActivity null exception warning?

Question

I have a fragment where I'll do the following:

getActivity().runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                                }
                    });

Here I get for runOnUiThread a warning may produce NullPointerException. The code works without problems.Android Studio suggests I change the code like this:

Objects.requireNonNull(getActivity()).runOnUiThread(new Runnable() {
                        @Override
                        public void run() {

is that sensible ? is there any other/better way ?

Hocine B · Accepted Answer · 2019-10-08T07:12:05.093

It depends on what your objective is :

1) You want the method caller to know he made a mistake by calling this method at a wrong state where getActivity()

private void myMethod() {
    if(null == getActivity()) {
        throw new IllegalStateException("Trying to call getActivity() at a state where the Activity equals null"); // Or new NullPointerException("")
    }
    // Do your stuff with getActivity()
}

2) You know that getActivity() will not throw a NullPointerException in your case :

private void myMethod() {
    assert getActivity() != null;
    // Do your stuff with getActivity()
}

3) You know that getActivity() may be null, you don't want the app to suddenly stop :

private void myMethod() {
    if(null == getActivity()) {
        return;
    }
    // Do your stuff with getActivity()
}

Using Objects.requireNonNull() also requires api level 19 (4.4 (KITKAT))

You also have tons of information right here

score 2 · Answer 2 · answered Oct 15 '18 at 17:12

You could just add a null check, which may be more understandable.

if(getActivity() != null) {
      getActivity().runOnUiThread(new Runnable() {
                 @Override
                 public void run() {
                                }
        });
}

But also, you can use the method #requireActivity() This works as a getActivity but if the activity is null (if the fragment is detached) it will throw an IllegalStateException

https://developer.android.com/reference/android/support/v4/app/Fragment#requireActivity()

Mable John · Answer 3 · 2019-10-08T04:45:03.763

(1) Use Flag isAdded(fragment is added to host activity) before getActivity(). This helps to avoid null pointer exception if the fragment is detached from the host activity.

if (isAdded() && null != getActivity()) {
   // your logic
}

(2) requireNonNull(T obj) Checks that the specified object reference is not null. This method is designed primarily for doing parameter validation in methods and constructors.

Throws NullPointerException - if obj is null(application execution may terminate at this point).

Summary: As per your current context requireNonNull(T obj) is not suitable. You must handle null pointer gracefully.

getActivity null exception warning?

3 Answers3