ListView is empty even when there is data in arrayList

Question

In my ChatListActivity, I am getting emails of users and showing them in a listView using Firebase. There is value in Firebase because when the arraylist is showing its data when I use log, but isn't showing in ListView. Please help.

    public class ChatListActivity extends AppCompatActivity {

    ListView userListView;
    ArrayAdapter<String> arrayAdapter;
    ArrayList<String> users = new ArrayList<>();
    FirebaseAuth mAuth;
    DatabaseReference databaseReference;
    Button signOut;

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

        mAuth = FirebaseAuth.getInstance();
        databaseReference = FirebaseDatabase.getInstance().getReference();
        userListView = findViewById(R.id.userListView);
        signOut = findViewById(R.id.signOut);

        databaseReference.child("users").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                if (snapshot.exists()){
                    for (DataSnapshot dataSnapshot : snapshot.getChildren()){
                        String email = dataSnapshot.child("email").getValue().toString();
                        if (!email.equals(FirebaseAuth.getInstance().getCurrentUser().getEmail())){
                            users.add(email);
                            Log.i("Log", Arrays.toString(new ArrayList[]{users}));
                        }
                    }
                    arrayAdapter = new ArrayAdapter<>(ChatListActivity.this, android.R.layout.simple_list_item_1, users);
                    userListView.setAdapter(arrayAdapter);
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Toast.makeText(ChatListActivity.this, "Failed to load users", Toast.LENGTH_SHORT).show();
            }
        });

        signOut.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mAuth.signOut();
                Intent intent = new Intent(ChatListActivity.this, MainActivity.class);
                startActivity(intent);
            }
        });
    }
}

Here is my log.

Brendon · Accepted Answer · 2021-05-28 13:49:05Z

1

Do set an empty adapter before network call, like this

arrayAdapter = new ArrayAdapter<>(ChatListActivity.this, android.R.layout.simple_list_item_1, users);
userListView.setAdapter(arrayAdapter);

after you receive original response, reset the adapter with new data. That should work.

now "users" will have some data

arrayAdapter = new ArrayAdapter<>(ChatListActivity.this, android.R.layout.simple_list_item_1, users);
userListView.setAdapter(arrayAdapter);

answered May 28, 2021 at 13:49

Brendon

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