FirebaseQuery观察者未删除

import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.Query;
import com.google.firebase.firestore.QuerySnapshot;
import com.google.firebase.firestore.DocumentChange;
import com.google.firebase.firestore.ListenerRegistration;

public class MyActivity extends AppCompatActivity {

    private ListenerRegistration listenerRegistration;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FirebaseFirestore db = FirebaseFirestore.getInstance();
        Query query = db.collection("myCollection");

        // 添加观察者
        listenerRegistration = query.addSnapshotListener((querySnapshot, e) -> {
            if (e != null) {
                Log.w(TAG, "Listen failed.", e);
                return;
            }

            for (DocumentChange dc : querySnapshot.getDocumentChanges()) {
                switch (dc.getType()) {
                    case ADDED:
                        Log.d(TAG, "New doc: " + dc.getDocument().getData());
                        break;
                    case MODIFIED:
                        Log.d(TAG, "Modified doc: " + dc.getDocument().getData());
                        break;
                    case REMOVED:
                        Log.d(TAG, "Removed doc: " + dc.getDocument().getData());
                        break;
                }
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 删除观察者
        if (listenerRegistration != null) {
            listenerRegistration.remove();
        }
    }
}