Android FragmentManager BackStackRecord.run throwing NullPointerException
Solution 1:
Answering my own question:
This exception is (eventually) thrown when you call FragmentTransaction.remove(null);
and FragmentTransaction.commit();
EDIT: And also, like Twice Circled and shinyuX point out in the comment; when calling the show(null)
or add(null)
, attach(null)
and detach(null)
methods, and probably also hide(null)
After calling commit()
, the transaction will be queued in the FragmentManager. As a result, when the operation is being processed after you explicitly call FragmentManager.executePendingTransactions()
, or when the FragmentManager queue thread calls it, it throws a NullPointerException
.
In my case, I was maintaining fragment states in a global object. There I checked if the fragment was showing or not, and then removed visible fragments. But because I started a new FragmentActivity, these states were still set to true while they were not visible. So this is a design error.
Other than fixing the design error, the solution was simple: check whether FragmentManager.findFragmentByTag()
returned null
before removing the fragment.