I am using an ArrayList (in Android) that contains the values from the Firebase database. Whenever the data is added or deleted, I want the list to be updated. To do this I used ChildEventListener but I am unsure whether this is a proper way of doing it as I face errors sometimes while deleting the elements from the list. There's no problem at all when adding elements to the list. But When I try to delete the last element from the list, I get ArrayIndexOutOfBounds Exception or some other Exception like length=12 index=-1. So, please go through my code and suggest a better way to delete elements:
public class Join extends AppCompatActivity {
DatabaseReference databaseReference;
ListView listView;
public static ArrayList<String> keysArrayList;
//To store the keys from Firebase
public static ArrayList<String> namesArrayList;
//To store the value or name associated with the key
ArrayAdapter<String> arrayAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_join);
databaseReference = FirebaseDatabase.getInstance().getReference().child(“Queue Codes”);
listView = (ListView) findViewById(R.id.listViewForMember);
keysArrayList = new ArrayList<>();
namesArrayList = new ArrayList<>();
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>
(this,android.R.layout.activity_list_item,namesArrayList);
listView.setAdapter(arrayAdapter);
/* Here I am trying to store Random keys from Firebase in
‘keysArrayList’ and their values in ‘namesArrayList’ and update these
lists whenever a value is added or removed from the database*/
databaseReference.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String addedKey = dataSnapshot.getKey();
String addedName = dataSnapshot.getValue(String.class);
keysArrayList.add(addedKey);
namesArrayList.add(addedName);
arrayAdapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
String removedKey = dataSnapshot.getKey();
int index = keysArrayList.indexOf(removedKey);
namesArrayList.remove(index);
keysArrayList.remove(removedKey);
arrayAdapter.notifyDataSetChanged();
/* Here I tried to remove the name from the ‘namesArrayList’ by
using the index of removed value from ‘keysArrayList’ as both
the lists would be of the same size anytime. I can simply
delete the name from the ‘namesArrayList’ by reading the
removed value from firebase but gets difficult when I use
Custom Array Lists which may contain many other objects. So, I
decided to delete the name using key index. */
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
