java - Application crashes whenever i sign out

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65862367/application-crashes-whenever-i-sign-out

Answer 1

Note that the onEvent method is called with two arguments:

public void onEvent(@Nullable DocumentSnapshot documentSnapshot, @Nullable FirebaseFirestoreException e) {
    name.setText(documentSnapshot.getString("name"));
    age.setText(documentSnapshot.getString("age"));
    gender.setText(documentSnapshot.getString("gender"));
    country.setText(documentSnapshot.getString("country"));
    school.setText(documentSnapshot.getString("school"));
}

You're completely ignoring the FirebaseFirestoreException, which explains the problem.

Most likely you require that the user is signed in, in order for them to be able to read the document. This means that once the user signs out, they lose their permission, and the database rejects the listener. This means your onEvent gets called again, this time with a FirebaseFirestoreException instead of a DocumentSnapshot.

So you should check the error, and only process the document when there was no error:

public void onEvent(@Nullable DocumentSnapshot documentSnapshot, @Nullable FirebaseFirestoreException e) {
  if (e != null) {
    name.setText(documentSnapshot.getString("name"));
    age.setText(documentSnapshot.getString("age"));
    gender.setText(documentSnapshot.getString("gender"));
    country.setText(documentSnapshot.getString("country"));
    school.setText(documentSnapshot.getString("school"));
  }
  else {
    Log.e("Firestore", "Error reading from Firestore", e);
  }
}

Troubleshooting NullPointerException almost always follows the same patter, so I recommend studying What is a NullPointerException, and how do I fix it? to learn how to figure something like this out on your own.