Hello I'm having this error when calling adpater on onStart does anyone know how I can fix it? Thank you very much in advance. Every help is welcome. I've been trying to find a solution but all that I apply cause the same mistake. I do not know what else to do.
error on calling adapter.startListening(); in onStart.
error logcat:> Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.firebase.ui.database.FirebaseRecyclerAdapter.startListening()' on a null object reference
public class FindFriendsActivity extends AppCompatActivity
{
FirebaseRecyclerAdapter<Contacts, FindFriendViewHolder> adapter;
private Toolbar mToolbar;
private RecyclerView FindFriendsRecyclerList;
private DatabaseReference UsersRef;
private SearchView searchView;
private Query query;
private FirebaseRecyclerOptions<Contacts> options;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_find_friends);
UsersRef = FirebaseDatabase.getInstance().getReference().child("Users");
FindFriendsRecyclerList = (RecyclerView) findViewById(R.id.find_friends_recycler_list);
FindFriendsRecyclerList.setLayoutManager(new LinearLayoutManager(this));
mToolbar = (Toolbar) findViewById(R.id.find_friends_toolbar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setTitle("Find Friends");
searchView = findViewById(R.id.materialSearchPrincipal);
}
private void fetch(Query query) {
FirebaseRecyclerOptions<Contacts > options =
new FirebaseRecyclerOptions.Builder<Contacts>()
.setQuery(query, new SnapshotParser<Contacts>() {
@RequiresApi(api = Build.VERSION_CODES.KITKAT)
@NonNull
@Override
public Contacts parseSnapshot(@NonNull DataSnapshot snapshot) {
return new Contacts(Objects.requireNonNull(snapshot.child("name").getValue()).toString(),
Objects.requireNonNull(snapshot.child("status").getValue()).toString());
}
})
.build();
adapter = new FirebaseRecyclerAdapter<Contacts, FindFriendViewHolder>(options) {
@Override
protected void onBindViewHolder(@NonNull FindFriendViewHolder holder, final int position, @NonNull Contacts model)
{
holder.userName.setText(model.getName());
holder.userStatus.setText(model.getStatus());
Picasso.get().load(model.getImage()).placeholder(R.drawable.profile_image).into(holder.profileImage);
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view)
{
String visit_user_id = getRef(position).getKey();
Intent profileIntent = new Intent(FindFriendsActivity.this, ProfileActivity.class);
profileIntent.putExtra("visit_user_id", visit_user_id);
startActivity(profileIntent);
}
});
}
@NonNull
@Override
public FindFriendViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i)
{
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.users_display_layout, viewGroup, false);
FindFriendViewHolder viewHolder = new FindFriendViewHolder(view);
return viewHolder;
}
};
adapter.startListening();
FindFriendsRecyclerList.setAdapter(adapter);
}
@Override
protected void onStart()
{
super.onStart();
adapter.startListening();
UsersRef = FirebaseDatabase.getInstance().getReference().child("Users");
Query query = FirebaseDatabase.getInstance().getReference().child("Users");
fetch(query);
}
public static class FindFriendViewHolder extends RecyclerView.ViewHolder
{
TextView userName, userStatus;
CircleImageView profileImage;
public FindFriendViewHolder(@NonNull View itemView)
{
super(itemView);
userName = itemView.findViewById(R.id.user_profile_name);
userStatus = itemView.findViewById(R.id.user_status);
profileImage = itemView.findViewById(R.id.users_profile_image);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
super.onCreateOptionsMenu(menu);
searchView.setOnQueryTextListener(new androidx.appcompat.widget.SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String s) {
return false;
}
@Override
public boolean onQueryTextChange(String s) {
Query query = FirebaseDatabase.getInstance()
.getReference()
.child("Users").orderByChild("name").equalTo(s);
if(s.equals("")){
query = FirebaseDatabase.getInstance()
.getReference()
.child("Users");
}
fetch(query);
return false;
}
});
return super.onCreateOptionsMenu(menu);
}
}
