public class ParticipatingGroupRepository implments ValueEventListener {
interface Listener {
void onSuccess(List<GroupId> groupIdList);
void onCancel(DatabaseError error);
}
private static final USERS_PATH = "users"
private static final PARTICIPATING_GROUPS_PATH = "participatingGroups"
private final DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference();
@Nullable
private Listener listener;
private ParticipatingGroupRepository() {
initParticipatingGroups();
}
private void initParticipatingGroups(){
dbRef.child(USERS_PATH)
.child(getCurrentUser().getUid())
.child(PARTICIPATING_GROUPS_PATH)
.addValueEventListener(this);
}
public void setListener(@Nullable Listener listener) {
this.lisetner = listener;
}
private FirebaseUser getCurrentUser() {
return FirebaseAuth.getInstance().getCurrentUser();
}
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
handleSuccess(snapshot);
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
if (lisetner == null) return;
listener.onCancel(error);
}
private void handleSuccess(DataSnapshot snapshot) {
List<GroupId> groupIdList = new ArrayList<GroupId>();
for(DataSnapshot dataSnapshot : snapshot.getChildren()){
GroupId groupId = dataSnapshot.getValue(GroupId.class);
if(groupId!=null) {
groupIdList.add(groupId);
}
}
if (lisetner == null) return;
listener.onSuccess(groupIdList)
}
}
public class ParticipantsRecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private final List<GroupId> groupIdList = new ArrayList<>();
public void submitList(List<GroupId> groupIdList) {
this.groupIdList.clear();
this.groupIdList.addAll(groupIdList);
notifyDataSetChanged();
}
...
}
public class MainActivity extends AppCompatActivity implements ParticipatingGroupRepository.Listener {
private ParticipatingGroupRepository participatingGroupRepository;
private ParticipantsRecyclerViewAdapter participantsRecyclerViewAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
participatingGroupRepository = new ParticipatingGroupRepository();
setupViews();
}
private void setupView() {
participantsRecyclerViewAdapter = new ParticipantsRecyclerViewAdapter();
}
@Override
public void onShow() {
super.onShow();
participatingGroupRepository.setListener(this);
}
public void onStop() {
super.onStop();
participatingGroupRepository.setListener(null);
}
@Override
public void onSuccess(List<GroupId> groupIdList) {
participantsRecyclerViewAdapter.submitList(groupIdList);
}
@Override
public void onCancel(DatabaseError error) {
}
}
