why use WeakReference on android Listeners?

I am working on a large code base, and see in many places this type of code:

public static class RequestCustomData implements View.OnClickListener {
    WeakReference<MainActivity> mainActivity;

    public RequestCustomData(MainActivity activity) {
        mainActivity = new WeakReference<>(activity);
    }

    @Override
    public void onClick(View view) {
        MainActivity activity = mainActivity.get();
        activity.requestCustomData(true, null);
    }
}

I am a bit confused why this is used is so many places? I took a look at this document but it did not clarify well why this type of code is so heavily used on the app I am working on it

https://community.oracle.com/blogs/enicholas/2006/05/04/understanding-weak-references

Anyone can explain me if this is a common pattern? If so, why?