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Recyclerview fetch existing data after delete an item from adapter and does not update properly

I try to implement a friend request feature in the fragment using custom adapter with firebase database. The problem is when a user accepts or delete someone request, it deletes from firebase but not properly update in the RecyclerView. this problems occurred in only runtime. If I refresh the page then my problem goes away.
Let I have two friend request. If I delete 2nd data then 2nd data will gone from RecyclerView but the problem is RecyclerView shows 1st data doubles. and if I delete 1st data then 1st data goes in the 2nd row and 2nd data came into the first row.
here is my database screenshot
Fragment class-
public class NotificationFragment extends Fragment {
private RecyclerView NotificationRecyclerView;
private NotificationAdapter adapter;
private List<Friend> friendList;
public NotificationFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_notification, container, false);
NotificationRecyclerView = view.findViewById(R.id.NotificationRecyclerView);
NotificationRecyclerView.setHasFixedSize(true);
LinearLayoutManager LayoutManager = new LinearLayoutManager(getContext());
NotificationRecyclerView.setLayoutManager(LayoutManager);
friendList = new ArrayList<>();
adapter = new NotificationAdapter(getContext(), friendList);
NotificationRecyclerView.setAdapter(adapter);
readAllNotification();
return view;
}
private void readAllNotification() {
final FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("FriendRequest");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
Friend friend = snapshot.getValue(Friend.class);
if (firebaseUser.getUid().equals(friend.getReceiverID())) {
friendList.add(friend);
}
}
Collections.reverse(friendList);
adapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
}
Custom Adapter -
public class NotificationAdapter extends RecyclerView.Adapter<NotificationAdapter.NotificationViewHolder> {
private Context context;
private List<Friend> friendList;
public NotificationAdapter(Context context, List<Friend> friendList) {
this.context = context;
this.friendList = friendList;
}
#NonNull
#Override
public NotificationViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(context).inflate(R.layout.single_notification_item, parent, false);
return new NotificationAdapter.NotificationViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull final NotificationViewHolder holder, final int position) {
final Friend friend = friendList.get(position);
getUserInfo(holder.profileImage, holder.NotificationUserName, friend.getSenderID());
holder.cancelRequestButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FirebaseDatabase.getInstance().getReference("FriendRequest")
.child(friend.getRequestID()).removeValue().addOnCompleteListener(new OnCompleteListener<Void>() {
#Override
public void onComplete(#NonNull Task<Void> task) {
removeItem(position);
Toast.makeText(context, "removed", Toast.LENGTH_SHORT).show();
}
});
}
});
}
public void removeItem(int position) {
friendList.remove(position);
notifyDataSetChanged();
}
#Override
public int getItemCount() {
return friendList.size();
}
private void getUserInfo(final CircleImageView prfileImage, final TextView NotificationUserName, String senderID) {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users").child(senderID);
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
Users users = dataSnapshot.getValue(Users.class);
NotificationUserName.setText(users.getUserName());
Picasso.with(context).load(users.getImageUrl()).into(prfileImage);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
public class NotificationViewHolder extends RecyclerView.ViewHolder {
private TextView NotificationUserName;
private Button cancelRequestButton;
private CircleImageView profileImage;
public NotificationViewHolder(#NonNull View itemView) {
super(itemView);
NotificationUserName = itemView.findViewById(R.id.NotificationUserName);
cancelRequestButton = itemView.findViewById(R.id.cancelRequestBtn);
profileImage = itemView.findViewById(R.id.profileImage);
}
}
}
My APP Problems screenshot -
let I have two request
1) if I delete 2nd data 1st data show doubles:
2) if I delete 1st data, 1st data goes into 2nd row and 2nd data came into 1st row:

Replace
removeItem(position);
with
removeItem(holder.getAdapterPosition());

You initialize your recyclerView and adapter in onCreateView which was not appropriate.You have to override the method onViewCreated then initialize your recyclerView and adapter.try like this
public class NotificationFragment extends Fragment {
private RecyclerView NotificationRecyclerView;
private NotificationAdapter adapter;
private List<Friend> friendList;
public NotificationFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_notification, container, false);
return view;
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
NotificationRecyclerView = view.findViewById(R.id.NotificationRecyclerView);
NotificationRecyclerView.setHasFixedSize(true);
LinearLayoutManager LayoutManager = new LinearLayoutManager(getContext());
NotificationRecyclerView.setLayoutManager(LayoutManager);
friendList = new ArrayList<>();
adapter = new NotificationAdapter(getContext(), friendList);
NotificationRecyclerView.setAdapter(adapter);
readAllNotification();
}
private void readAllNotification() {
final FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("FriendRequest");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
Friend friend = snapshot.getValue(Friend.class);
if (firebaseUser.getUid().equals(friend.getReceiverID())) {
friendList.add(friend);
}
}
Collections.reverse(friendList);
adapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
Ok I just noticed you passed a parameter in removeItem method using holder.getAdapterPosition() which is causing your problem.Try to pass the position which is provided by public void onBindViewHolder(#NonNull final NotificationViewHolder holder, final int position).So the basic error is when you are in onBindViewHolder you don't need to use holder.getAdapterPosition() because onBindViewHolder already giving you the position
In your removeItem method use notifyDataSetChanged instead of notifyItemRemoved(position)
try like this
#Override
public void onBindViewHolder(#NonNull final NotificationViewHolder holder, final int position) {
final Friend friend = friendList.get(position);
holder.cancelRequestButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FirebaseDatabase.getInstance().getReference("FriendRequest").child(friend.getRequestID()).removeValue().addOnCompleteListener(new OnCompleteListener<Void>() {
#Override
public void onComplete(#NonNull Task<Void> task) {
removeItem(position);
Toast.makeText(context, "removed", Toast.LENGTH_SHORT).show();
}
});
}
});
}
public void removeItem(int position) {
friendList.remove(position);
notifyDataSetChanged();
}

Unable to fetch Object id of post in android using mongoDb NodeJs as a backend

I am making an android app where I am using MongoDB and NodeJs as a backend service.I have some posts saved on MongoDb and I am retrieving them in recycler view.I have a button in recycler view when it is clicked I want to fetch an Object Id of an item.
I am successfully fetching all documents in recycler view but the problem is
when I clicked on button in particular item.They are showing Object Id of a document which is inserted recently and not showing correct Object Id of an item.
This is what I have done so far:
MyPostBookAdapter.java
public class MyPostedBookAdapter extends RecyclerView.Adapter<MyPostedBookAdapter.ViewHolder> {
List<PostedModel> listItem;
Activity context;
String id;
public MyPostedBookAdapter(List<PostedModel> listItem, Activity context){
this.listItem = listItem;
this.context = context;
}
#NonNull
#Override
public MyPostedBookAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.posted_book,viewGroup,false);
return new ViewHolder(v);
}
#Override
public void onBindViewHolder(#NonNull final MyPostedBookAdapter.ViewHolder viewHolder, final int i) {
final PostedModel model = listItem.get(i);
//Object Id of post
id = model.getPostId();
viewHolder.userBookName.setText(model.getPurchaseBookName());
RequestOptions requestOptions = new RequestOptions();
requestOptions.placeholder(R.drawable.openbook);
Glide.with(context).load(model.getPurchaseImage()).apply(requestOptions).into(viewHolder.userPostBook);
viewHolder.delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(context,id,Toast.LENGTH_SHORT).show();
}
});
}
#Override
public int getItemCount() {
return listItem.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
ImageView userPostBook;
TextView userBookName;
Button delete;
public ViewHolder(#NonNull View itemView) {
super(itemView);
userPostBook = (itemView).findViewById(R.id.userPostBook);
userBookName = (itemView).findViewById(R.id.userBookName);
delete = (itemView).findViewById(R.id.delete);
}
}
}
PostedModel.java
public class PostedModel {
String purchaseImage,purchaseBookName,postId;
public PostedModel(){
}
public PostedModel(String purchaseImage, String purchaseBookName,String postId){
this.purchaseBookName = purchaseBookName;
this.purchaseImage = purchaseImage;
this.postId = postId;
}
public String getPurchaseImage() {
return purchaseImage;
}
public void setPurchaseImage(String purchaseImage) {
this.purchaseImage = purchaseImage;
}
public String getPurchaseBookName() {
return purchaseBookName;
}
public void setPurchaseBookName(String purchaseBookName) {
this.purchaseBookName = purchaseBookName;
}
public String getPostId() {
return postId;
}
public void setPostId(String postId) {
this.postId = postId;
}
}
Please let me know how can I get ObjectId correspond to right item.
Any help would be appreciated.
THANKS

The Issue is,
Recycler view load every object given one by one, so variable id had the value of last object. So you need to take id from the selected view.
The Fix is,
#Override
public void onBindViewHolder(#NonNull final MyPostedBookAdapter.ViewHolder viewHolder, final int i) {
final PostedModel model = listItem.get(i);
//Object Id of post
id = model.getPostId();
// You need to set this id to viewHolder.
viewHolder.userBookName.setId(id);
viewHolder.userBookName.setText(model.getPurchaseBookName());
RequestOptions requestOptions = new RequestOptions();
requestOptions.placeholder(R.drawable.openbook);
Glide.with(context).load(model.getPurchaseImage()).apply(requestOptions).into(viewHolder.userPostBook);
viewHolder.delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Here you can extract the id which we set at binding
int idOfView = v.userBookName.getId();
Toast.makeText(context,idOfView,Toast.LENGTH_SHORT).show();
}
});
}
Hope this will help you.

RecyclerView not showing data until turn off and turn on screen

I am developing an app that shows in a RecyclerView an image and a text that comes from firebase.
When I open the application the recyclerview does not appear but if I turn off and then turn on the screen the recyclerview appears correctly with the image and text obtained from firebase. I need help please
ViewHolder:
public class ViewHolderServicio extends RecyclerView.ViewHolder {
View mView;
public ViewHolderServicio(#NonNull View itemView) {
super(itemView);
mView = itemView;
}
public void setDetails(Context ctx, String nombreServicio, String imagenPerfil) {
TextView mNombreServicio = mView.findViewById(R.id.NombreServicio);
ImageView mImagenPerfil = mView.findViewById(R.id.imageViewServicio);
mNombreServicio.setText(nombreServicio);
Picasso.get().load(imagenPerfil).into(mImagenPerfil);
}
}
Model:
public class ModelServicio {
String idUsuario, nombreServicio, descripcion, imagenPerfil;
public ModelServicio(){}
public String getIdUsuario() {
return idUsuario;
}
public void setIdUsuario(String idUsuario) {
this.idUsuario = idUsuario;
}
public String getNombreServicio() {
return nombreServicio;
}
public void setNombreServicio(String nombreServicio) {
this.nombreServicio = nombreServicio;
}
public String getDescripcion() {
return descripcion;
}
public void setDescripcion(String descripcion) {
this.descripcion = descripcion;
}
public String getImagenPerfil() {
return imagenPerfil;
}
public void setImagenPerfil(String imagenPerfil) {
this.imagenPerfil = imagenPerfil;
}
}
class activity:
public class DetalleServicio extends AppCompatActivity {
RecyclerView RVbot;
FirebaseDatabase mFirebaseDatabase;
DatabaseReference mRef;
FirebaseRecyclerAdapter<ModelServicio, ViewHolderServicio> firebaseRecyclerAdapter;
FirebaseRecyclerOptions<ModelServicio> options;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detalle_servicio);
RVbot = findViewById(R.id.RVBot);
RVbot.setHasFixedSize(true);
RVbot.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
mFirebaseDatabase = FirebaseDatabase.getInstance();
mRef = mFirebaseDatabase.getReference("Servicios");
mostrarDatos();
}
private void mostrarDatos() {
options = new FirebaseRecyclerOptions.Builder<ModelServicio>().setQuery(mRef, ModelServicio.class).build();
firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<ModelServicio, ViewHolderServicio>(options) {
#Override
protected void onBindViewHolder(#NonNull ViewHolderServicio holder, int position, #NonNull ModelServicio model) {
holder.setDetails(getApplicationContext(), model.getNombreServicio(), model.getImagenPerfil());
}
#NonNull
#Override
public ViewHolderServicio onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View itemView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.servicioitem, viewGroup, false);
ViewHolderServicio viewHolder = new ViewHolderServicio(itemView);
return viewHolder;
}
};
RVbot.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
}
#Override
protected void onStart() {
super.onStart();
firebaseRecyclerAdapter.startListening();
RVbot.setAdapter(firebaseRecyclerAdapter);
}
}

Have you tried
firebaseRecyclerAdapter.notifyDataSetChanged();
after calling an Adapter?

Data successfully retrieved from database but can't pass through the adapter class

Well... i want to show data retrieved from firebase database in RecycleView and do further stuffs like editing,updating etc. So, i'm using observable pattern to retrieve data(which successfully did) and trying to pass data to the constructor and the adapter class. The data did show up in the constructor class but didn't load in adapter class and also in the RecycleView.
Fragment class or main class
public class overviewFragment extends Fragment {
View view;
public static RecyclerView overRecycleView;
public overviewFragment() {}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
view = inflater.inflate(R.layout.overview_fragment, container, false);
overRecycleView = view.findViewById(R.id.overViewRecycle);
overviewRecyclerAdapter adapter = new overviewRecyclerAdapter(getContext(), observerData.overViewlist);
overRecycleView.setLayoutManager(new LinearLayoutManager(getActivity()));
// adapter.notifyDataSetChanged();
overRecycleView.setAdapter(adapter);
return view;
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
observableData ob =new observableData();
observerData observerData = new observerData(ob)
ob.setMeasurement();
ob.setMeasurement(); }}
Observable class to retrieve firebase data and notify observer
public class observableData extends Observable {
private String data;
public observableData() { }
public void setMeasurement(){
final DatabaseReference n = ScrollingActivityforTutor.db();
n.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String a = dataSnapshot.child("name").getValue().toString();
Log.d("name from database ", a);
data =a;
measurementChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
public void measurementChanged(){
setChanged();
notifyObservers();
}
public String getData() {
return data;
}
}
Observer class from where constructor class will be called
public class observerData implements Observer {
Observable observable;
public String data;
public static List<itemOverview> overViewlist = new ArrayList<>();;
public observerData(Observable observable) {
this.observable = observable;
observable.addObserver(this);
}
#Override
public void update(Observable o, Object arg) {
observableData od = (observableData) o;
this.data = od.getData();
passData();
}
public void passData(){
overViewlist.add(new itemOverview(data));
Log.d("data in observer ", data);
}
}
Constructor class
public class itemOverview {
private String text;
public itemOverview(String text) {
Log.d("IN CONSTRUCTOR ", text); // It is perfectly showing the data
this.text = text;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}}
Adapter class
public class overviewRecyclerAdapter extends
RecyclerView.Adapter<overviewRecyclerAdapter.overviewViewHolder> {
Context mcontext;
List<itemOverview> mdata;
public overviewRecyclerAdapter(Context mcontext, List<itemOverview> mdata)
{
this.mcontext = mcontext;
this.mdata = mdata; }
public static class overviewViewHolder extends RecyclerView.ViewHolder{
private TextView t;
public overviewViewHolder(#NonNull View itemView) {
super(itemView);
t = itemView.findViewById(R.id.overViewtextView); }}
#NonNull
#Override
public overviewRecyclerAdapter.overviewViewHolder
onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View v;
v = LayoutInflater.from(mcontext).inflate(R.layout.item_overview,
parent, false);
overviewViewHolder overview = new overviewViewHolder(v);
return overview; }
#Override
public void onBindViewHolder(#NonNull
overviewRecyclerAdapter.overviewViewHolder holder, int position) {
Log.d("IN ADAPTER ", mdata.get(position).getText()); // HERE, IT IS
NOT WORKING
holder.t.setText(mdata.get(position).getText());
}
#Override
public int getItemCount() {
return mdata.size() ;
}}
But when i use measurementChanged() (in the observable class) outside the onDatachange method and put data (variable) with some string value, everything worked and the given data showed up in the recycleView.
dont understand where the problem is and where to debug.
However, SORRY for such big miles of codes :)
Thanks.

I can see that you are trying to add elements to a RecyclerView programmatically. But the RecyclerView is not updated when you update the array containing the necessary data. As you have made the RecyclerView static, you can easily notify the changes to the adapter using the following code:
public void passData(){
overViewlist.add(new itemOverview(data));
Log.d("data in observer ", data);
overviewRecyclerAdapter adapter = (overviewRecyclerAdapter) overviewFragment.overRecycleView.getAdapter();
adapter.notifyDataSetChanged();
}
There are much better ways of doing this. adapter.notifyItemInserted(overViewlist.size()-1); is probably a better solution in your case (in terms of performance).
P.S. You should follow the naming conventions in java to make your code more readable.

Android Using View Holder

I try to show in my app using firebase but not return image or the other data
please help me I use it after no any error but now I do not use this method
public class PaylasAnaSayfa extends AppCompatActivity {
private RecyclerView mBlogList;
public DatabaseReference mDatabase;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_paylas_ana_sayfa);
mDatabase= FirebaseDatabase.getInstance().getReference().child("Resimler");
mBlogList= (RecyclerView) findViewById(R.id.resim_list);
mBlogList.setHasFixedSize(true);
mBlogList.setLayoutManager(new LinearLayoutManager(this));
if (mDatabase==null){
Toast.makeText(this, "veri tabanı hatası", Toast.LENGTH_SHORT).show();
}else {
FirebaseRecyclerAdapter<PaylasModel, PaylasHolder> adapter = new FirebaseRecyclerAdapter<PaylasModel, PaylasHolder>(
PaylasModel.class,
R.layout.resim_row,
PaylasHolder.class,
mDatabase
) {
#Override
protected void populateViewHolder(PaylasHolder viewHolder, PaylasModel model, int position) {
viewHolder.setImage(getApplicationContext(), model.getImgImage());
viewHolder.setBaslik(model.getImgBaslik());
viewHolder.setAciklama(model.getImgAciklama());
viewHolder.setKullanici(model.getImgKullaniciAdi());
viewHolder.setDers(model.getImgDers());
}
};
mBlogList.setAdapter(adapter);
}
}
private static class PaylasHolder extends RecyclerView.ViewHolder {
View mView;
public PaylasHolder(View itemView) {
super(itemView);
mView=itemView;
}
public void setBaslik(String baslik){
TextView tBaslik= (TextView) mView.findViewById(R.id.row_img_baslik);
tBaslik.setText(baslik);
}
public void setAciklama(String aciklama){
TextView tAciklama= (TextView) mView.findViewById(R.id.row_img_aciklama);
tAciklama.setText(aciklama);
}
public void setKullanici(String kullanici){
TextView tKullanici= (TextView) mView.findViewById(R.id.row_img_kullanici);
tKullanici.setText(kullanici);
}
public void setDers(String ders){
TextView tDers= (TextView) mView.findViewById(R.id.row_img_ders);
tDers.setText(ders);
}
public void setImage(final Context context, final String image){
final ImageView tImage= (ImageView) mView.findViewById(R.id.row_img_image);
Picasso.with(context).load(image).networkPolicy(NetworkPolicy.OFFLINE).into(tImage, new Callback() {
#Override
public void onSuccess() {
}
#Override
public void onError() {
Picasso.with(context).load(image).into(tImage);
}
});
}
}
}
using view holder do not return data
The word in square brackets is the alt text, which gets displayed if the browser can't show the image. Be sure to include meaningful alt text for screen-reading software.

First you don't need to initialize views everytime in the methods of your ViewHolder.RecyclerView reuses the view from the view pool.
private static class PaylasHolder extends RecyclerView.ViewHolder {
View mView;
TextView tBaslik;
public PaylasHolder(View itemView) {
super(itemView);
mView=itemView;
tBaslik = mView.findViewById(R.id.row_img_baslik);
//intialize all you view here once and for all.
}
public void setBaslik(String baslik){
tBaslik.setText(baslik);
}
public void setAciklama(String aciklama){
tAciklama.setText(aciklama);
}
public void setKullanici(String kullanici){
tKullanici.setText(kullanici);
}
public void setDers(String ders){
tDers.setText(ders);
}
public void setImage(final Context context, final String image){
Picasso.with(context).load(image).networkPolicy(NetworkPolicy.OFFLINE).into(tImage, new Callback() {
#Override
public void onSuccess() {
}
#Override
public void onError() {
Picasso.with(context).load(image).into(tImage);
}
});
}
}
If you are very much sure about the size of the recyclerview then only use setHasFixedSize(true) otherwise it will not request layout upon the addition of data to the adapter.