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I want to get the qna list through firebase, but I can't get the list

This is a list of qna in the firebase. I want to print this out.
But my output list doesn't show anything.
https://i.stack.imgur.com/6ctRB.png
QNA Activity
public class QnaActivity extends AppCompatActivity {
private RecyclerView qnaRv;
private ArrayList<ModelQna> qnaList;
private AdapterQna adapterQna;
private ImageButton writeBtn;
private ImageButton backbtn;
private TextView tabQnaTv;
private RelativeLayout QnaRl;
private FirebaseAuth firebaseAuth;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_qna);
getSupportActionBar().hide();
qnaRv = findViewById(R.id.qnaRv);
tabQnaTv = findViewById(R.id.tabQnaTv);
QnaRl = findViewById(R.id.QnaRl);
backbtn = findViewById(R.id.backBtn);
writeBtn = findViewById(R.id.writeBtn);
firebaseAuth = FirebaseAuth.getInstance();
loadAllQna();
showQnaUI();
backbtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
onBackPressed();
}
});
writeBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(), AddQnaActivity.class);
startActivity(intent);
}
});
tabQnaTv.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//load products
}
});
}
private void loadAllQna() {
qnaList = new ArrayList<>();
adapterQna = new AdapterQna(this, qnaList);
qnaRv.setAdapter(adapterQna);
//get all products
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Employees");
reference.child(firebaseAuth.getUid()).child("Qna").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
//before getting reset List
qnaList.clear();
for (DataSnapshot dataSnapshot : snapshot.getChildren()){
ModelQna modelQna = dataSnapshot.getValue(ModelQna.class);
qnaList.add(modelQna);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseerror) {
}
});
}
private void showQnaUI() {
//show orders ui and hide products ui
QnaRl.setVisibility(View.GONE);
}
}
Model
public class ModelFaq {
private String faqId,faqTitle,faqContent, timestamp,uid,faqCategory;
public ModelFaq() {
}
public ModelFaq(String faqId, String faqTitle, String faqContent, String timestamp, String uid, String faqCategory) {
this.faqId = faqId;
this.faqTitle = faqTitle;
this.faqContent = faqContent;
this.timestamp = timestamp;
this.uid = uid;
this.faqCategory = faqCategory;
}
public String getFaqId() {
return faqId;
}
public void setFaqId(String faqId) {
this.faqId = faqId;
}
public String getFaqTitle() {
return faqTitle;
}
public void setFaqTitle(String faqTitle) {
this.faqTitle = faqTitle;
}
public String getFaqContent() {
return faqContent;
}
public void setFaqContent(String faqContent) {
this.faqContent = faqContent;
}
public String getTimestamp() {
return timestamp;
}
public void setTimestamp(String timestamp) {
this.timestamp = timestamp;
}
public String getUid() {
return uid;
}
public void setUid(String uid) {
this.uid = uid;
}
public String getFaqCategory() {
return faqCategory;
}
public void setFaqCategory(String faqCategory) {
this.faqCategory = faqCategory;
}
}
Qna Adapter
public class AdapterQna extends RecyclerView.Adapter<AdapterQna.HolderQna> {
private Context context;
public ArrayList<ModelQna> qnaList;
public AdapterQna(Context context, ArrayList<ModelQna> qnaList) {
this.context = context ;
this.qnaList = qnaList ;
}
#NonNull
#Override
public HolderQna onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
//inflate layout
View view = LayoutInflater.from(context).inflate(R.layout.qna_item, parent, false);
return new HolderQna(view);
}
#Override
public void onBindViewHolder(#NonNull HolderQna holder, int position) {
ModelQna modelQna = qnaList.get(position);
String id = modelQna.getQnaId();
String uid = modelQna.getUid();
String qnaContent = modelQna.getQnaContent();
String qnaTitle = modelQna.getQnaTitle();
String timestamp = modelQna.getTimestamp();
//set data
holder.titleTextView.setText(qnaTitle);
holder.ContentTextView.setText(qnaContent);
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//handle item clicks, show item details
}
});
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//handle item clicks, show item details
}
});
}
#Override
public int getItemCount() {
return qnaList.size();
}
class HolderQna extends RecyclerView.ViewHolder{
/*holds views of recyclerview*/
private TextView titleTextView, ContentTextView;
public HolderQna(#NonNull View itemView) {
super(itemView);
titleTextView = itemView.findViewById(R.id.item_post_title);
ContentTextView = itemView.findViewById(R.id.item_post_content);
}
}
}

Can you please change the code in your HolderQna to:
class HolderQna extends RecyclerView.ViewHolder{
/*holds views of recyclerview*/
private TextView titleTextView, ContentTextView;
public HolderQna(#NonNull View itemView) {
super(itemView);
titleTextView = itemView.findViewById(R.id.item_post_title);
ContentTextView = itemView.findViewById(R.id.item_post_content);
}
public void bind(qna: ModelQna){
titleTextView.setText(qna.qnaTitle);
ContentTextView.setText(qna.qnaContent);
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//handle item clicks, show item details
}
});
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//handle item clicks, show item details
}
});
}
}
And your onBindViewHolder override of the AdapterQna to:
#Override
public void onBindViewHolder(#NonNull HolderQna holder, int position) {
ModelQna modelQna = qnaList.get(position);
String id = modelQna.getQnaId();
String uid = modelQna.getUid();
String qnaContent = modelQna.getQnaContent();
String qnaTitle = modelQna.getQnaTitle();
String timestamp = modelQna.getTimestamp();
//set data
holder.bind(modelQna);
}
Finally change your loadQna() function declaration as follows:
private void loadAllQna() {
qnaList = new ArrayList<>();
//get all products
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Employees");
reference.child(firebaseAuth.getUid()).child("Qna").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
//before getting reset List
qnaList.clear();
for (DataSnapshot dataSnapshot : snapshot.getChildren()){
ModelQna modelQna = dataSnapshot.getValue(ModelQna.class);
qnaList.add(modelQna);
}
adapterQna = new AdapterQna(this, qnaList);
qnaRv.setAdapter(adapterQna);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseerror) {
Log.e("QnaActivity", databaseError.toString());
}
});
}

As far as I can see in your screenshot, the Qna node it's not nested under any UID, but directly under the Employees node. So when you attach a listener to the following node:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Employees");
reference.child(firebaseAuth.getUid()).child("Qna").addValueEventListener(/*...*/);
You will not be able to get any results, because such a reference doesn't exist. To solve this, you either create a reference that points exactly to "Qna":
DatabaseReference db = FirebaseDatabase.getInstance().getReference();
DatabaseReference qnaRef = db.child("Employees").child("Qna");
qnaRef.addValueEventListener(/*...*/);
Or you move the "Qna" node under the UID of the user, and leave the code unchanged.
Besides that, there is also another problem. The name of the fields in your ModelFaq class are different than the name of the properties in your database. You have in your ModelFaq class four fields called faqId, faqTitle, faqContent, faqCategory, all starting with faq while in the database I see that the names are different, qnaId, qnaTitle, qnaContent, qnaCategory, all are starting wiht qna, and this is not correct. So in order to be able to map a node into an object of type ModelFaq, the names must match. The only two fields that match are the timestamp and the uid.
In this case, you have two solutions. The first one would to change the name of your fieds in the ModelFaq class according to what it already exists in the database or you can use the PropertyName annotation in front of the getters like this:
#PropertyName("qnaId")
public String getFaqId() {
return faqId;
}

RecyclerView showing data after closing and coming back to activity

I am using RecyclerView to show data that is fetching from firebase Realtime Database. When I am opening recycler view activity it is showing nothing but when I go to previous activity come again then it is showing.
THIS IS THE ACTIVITY IN WHICH DATA HAS TO BE SHOWN-
public class BrakesItemActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private FloatingActionButton floatingActionButton;
private FirebaseDatabase database;
private DatabaseReference BrakestransactionDb, brakesDb;
private FirebaseRecyclerOptions<Transaction> options;
private FirebaseRecyclerAdapter<Transaction, TransactionViewHolder> adapter;
int sumofbrakescost = 0;
String sumofbrakescostvalue;
BottomAppBar bottomAppBar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_last2);
bottomAppBar = findViewById(R.id.bottom_app_bar);
recyclerView = findViewById(R.id.recycler_view);
floatingActionButton = findViewById(R.id.floating_button);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS,
WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);
setSupportActionBar(bottomAppBar);
floatingActionButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(BrakesItemActivity.this, BInputActivity.class);
startActivity(intent);
}
});
database = FirebaseDatabase.getInstance();
BrakestransactionDb = database.getReference().child("Brakes Items Transaction");
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(BrakesItemActivity.this));
BrakestransactionDb.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = (Map<String, Object>) ds.getValue();
Object totalcost = map.get("totalcoststring");
int totalcostvalue = Integer.parseInt(String.valueOf(totalcost));
sumofbrakescost += totalcostvalue;
sumofbrakescostvalue = String.valueOf(sumofbrakescost);
}
brakesDb = database.getReference().child("Department").child("Brakes").child("Cost");
brakesDb.setValue(sumofbrakescostvalue);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
showTask();
}
private void showTask() {
options = new FirebaseRecyclerOptions.Builder<Transaction>().setQuery(BrakestransactionDb, Transaction.class).build();
adapter = new FirebaseRecyclerAdapter<Transaction, TransactionViewHolder>(options) {
#Override
protected void onBindViewHolder(#NonNull TransactionViewHolder holder, int position, #NonNull Transaction model) {
holder.item_name_card.setText(model.getNameofitemstring());
holder.bought_by_card.setText(model.getBoughtbystring());
holder.bought_from_card.setText(model.getBoughtfromstring());
holder.date_card.setText(model.getDatestring());
holder.time_card.setText(model.getTimestring());
holder.cost_of_one_item_card.setText(model.getCostofoneitemstring());
holder.number_of_items_card.setText(model.getNumberofitemstring());
holder.total_cost_card.setText(model.getTotalcoststring());
}
#NonNull
#Override
public TransactionViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.transaction_row, parent, false);
return new TransactionViewHolder(itemView);
}
};
recyclerView.setAdapter(adapter);
}
#Override
protected void onStart() {
super.onStart();
adapter.startListening();
}
#Override
protected void onStop() {
super.onStop();
adapter.stopListening();
}
#Override
public boolean onContextItemSelected(#NonNull MenuItem item) {
if (item.getTitle().equals("Delete")) {
deleteTransaction(adapter.getRef(item.getOrder()).getKey());
}
return super.onContextItemSelected(item);
}
private void deleteTransaction(String key) {
BrakestransactionDb.child(key).removeValue();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.bottommenu, menu);
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(#NonNull MenuItem item) {
if (item.getItemId() == R.id.delete_all) {
BrakestransactionDb.removeValue();
}
if (item.getItemId() == R.id.home_button) {
Intent intent = new Intent(this, NavActivity.class);
finish();
startActivity(intent);
if (item.getItemId() == R.id.back_item_activity) {
Intent intent1 = new Intent(this, Department.class);
finish();
startActivity(intent1);
}
}
return super.onOptionsItemSelected(item);
}
}
THIS IS THE MODEL CLASS I MADE-
package com.example.android.zfr.Model;
public class Transaction {
private String nameofitemstring,boughtbystring,boughtfromstring,costofoneitemstring,datestring,
timestring,totalcoststring,numberofitemstring;
public String getNameofitemstring() { return nameofitemstring; }
public void setNameofitemstring(String nameofitemstring) { this.nameofitemstring = nameofitemstring; }
public String getBoughtbystring() {return boughtbystring; }
public void setBoughtbystring(String bought string) {
this.boughtbystring = boughtbystring;
}
public String getBoughtfromstring() { return boughtfromstring; }
public void setBoughtfromstring(String boughtfromstring) { this.boughtfromstring = boughtfromstring; }
public String getCostofoneitemstring() {
return costofoneitemstring;
}
public void setCostofoneitemstring(String costofoneitemstring) { this.costofoneitemstring = costofoneitemstring; }
public String getDatestring() { return datestring; }
public void setDatestring(String datestring) { this.datestring = datestring; }
public String getTimestring() { return timestring; }
public void setTimestring(String timestring) { this.timestring = timestring; }
public String getTotalcoststring() { return totalcoststring; }
public void setTotalcoststring(String totalcoststring) { this.totalcoststring = totalcoststring; }
public String getNumberofitemstring() { return numberofitemstring; }
public void setNumberofitemstring(String numberofitemstring) { this.numberofitemstring = numberofitemstring; }
public Transaction() { }
public Transaction(String nameofitemstring,String boughtbystring,String boughtfromstring,String costofoneitemstring, String timestring,
String datestring ,String totalcoststring , String numberofitemstring ){
this.nameofitemstring=nameofitemstring;
this.boughtbystring=boughtbystring;
this.boughtfromstring=boughtfromstring;
this.costofoneitemstring=costofoneitemstring;
this.datestring=datestring;
this.timestring=timestring;
this.numberofitemstring=numberofitemstring;
this.totalcoststring=totalcoststring;
}
}
THIS THE VIEWHOLDER CLASS-
package com.example.android.zfr.ViewHolder;
import android.view.ContextMenu;
import android.view.View;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.example.android.zfr.R;
import com.facebook.shimmer.ShimmerFrameLayout;
public class TransactionViewHolder extends RecyclerView.ViewHolder implements
View.OnCreateContextMenuListener{
public TextView item_name_card,bought_by_card,bought_from_card,date_card,
time_card,cost_of_one_item_card,number_of_items_card,total_cost_card;
public TransactionViewHolder(#NonNull View itemView) {
super(itemView);
item_name_card=itemView.findViewById(R.id.item_name_card);
bought_by_card=itemView.findViewById(R.id.bought_by_card);
bought_from_card=itemView.findViewById(R.id.bought_from_card);
date_card=itemView.findViewById(R.id.date_card);
time_card=itemView.findViewById(R.id.time_card);
cost_of_one_item_card=itemView.findViewById(R.id.cost_of_one_item_card);
number_of_items_card=itemView.findViewById(R.id.number_of_items_card);
total_cost_card=itemView.findViewById(R.id.total_cost_card);
itemView.setOnCreateContextMenuListener(this);
}
#Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo)
{ menu.add(0,0,getAdapterPosition(),"Delete"); }
}
Please help.

you need to realize that Firebase is Asynchronous, meaning that your showTask() gets called even before your database is able to send you the data. To avoid this issue, you need to put your showTask() inside your addValueEventListener. Try this:
BrakestransactionDb.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = (Map<String, Object>) ds.getValue();
Object totalcost = map.get("totalcoststring");
int totalcostvalue = Integer.parseInt(String.valueOf(totalcost));
sumofbrakescost += totalcostvalue;
sumofbrakescostvalue = String.valueOf(sumofbrakescost);
}
brakesDb = database.getReference().child("Department").child("Brakes").child("Cost");
brakesDb.setValue(sumofbrakescostvalue);
showTask();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

It worked by putting
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(BrakesItemActivity.this));
in onDatachange method like this:
BrakestransactionDb.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = (Map<String, Object>) ds.getValue();
Object totalcost = map.get("totalcoststring");
int totalcostvalue = Integer.parseInt(String.valueOf(totalcost));
sumofbrakescost += totalcostvalue;
sumofbrakescostvalue = String.valueOf(sumofbrakescost);
}
brakesDb = database.getReference().child("Department").child("Brakes").child("Cost");
brakesDb.setValue(sumofbrakescostvalue);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(BrakesItemActivity.this));
}

How to prevent drawables from refreshing on recyclerview?

I made a button, which when clicked changes values on the database,
the status/color of the button is based on the value on the database.
How to prevent all drawables from getting refreshed on recyclerview just because one drawable had its value changed?
Result i get:
https://media.giphy.com/media/frHERBcrLUA8x14bsh/giphy.gif
public MainAdapter(Context mContext, List<Posts> mPost)
{
Log.d(TAG, "Main Adapter Start");
this.mContext = mContext;
this.mPost = mPost;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(mContext).inflate(R.layout.all_posts_layout, viewGroup, false);
return new MainAdapter.ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull final ViewHolder holder, final int position) {
mAuth = FirebaseAuth.getInstance();
currentUserID = mAuth.getCurrentUser().getUid();
final Posts post = mPost.get(position);
final String Postkey = post.getPost_uid();
final String likes = Integer.toString(post.getLikes());
holder.setUpStatus(Postkey);
LikesRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
holder.LikepostButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
LikeChecker = true;
LikesRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
if (LikeChecker.equals(true))
{
if (dataSnapshot.child(Postkey).hasChild(currentUserID)) {
LikesRef.child(Postkey).child(currentUserID).removeValue();
PostsRef.child(Postkey).child("likes").setValue(post.getLikes()-1);
LikeChecker = false;
} else {
LikesRef.child(Postkey).child(currentUserID).setValue(true);
DisikesRef.child(Postkey).child(currentUserID).removeValue();
StoreToHistory(Postkey);
DisikesRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.child(currentUserID).exists())
{
PostsRef.child(Postkey).child("likes").setValue(post.getLikes()+2);
}
else {
PostsRef.child(Postkey).child("likes").setValue(post.getLikes()+1);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
LikeChecker = false;
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}});
}
#Override
public void onCancelled(DatabaseError databaseError) {}
});
}
#Override
public int getItemCount()
{
return mPost.size();
}
ViewHolder:
public class ViewHolder extends RecyclerView.ViewHolder {
View mView;
ImageButton LikepostButton, DislikepostButton;
int countLikes, countDislikes, countComms;
public ViewHolder(View itemView) {
super(itemView);
mView = itemView;
currentUserId = FirebaseAuth.getInstance().getCurrentUser().getUid();
LikepostButton = itemView.findViewById(R.id.like_button);
DislikepostButton = itemView.findViewById(R.id.dislike);
CommentPostButton = itemView.findViewById(R.id.comment_button);
DisplayNoOfLikes = itemView.findViewById(R.id.display_number_of_likes);
DisplayNoOfDislikes = itemView.findViewById(R.id.display_number_of_dislikes);
}
public void setUpStatus(final String PostKey)
{
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Ups");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.child(PostKey).hasChild(currentUserID))
{
LikepostButton.setImageResource(R.drawable.upvote);
DisplayNoOfLikes.setTextColor(Color.parseColor("#f14c00"));
}
else
{
LikepostButton.setImageResource(R.drawable.upvote_novote);
}
DisikesRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.child(PostKey).hasChild(currentUserID))
{
DislikepostButton.setImageResource(R.drawable.downvote_orange);
DisplayNoOfLikes.setTextColor(Color.parseColor("#df3168a7"));
}
else {
DislikepostButton.setImageResource(R.drawable.downvote_novote);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
}); }
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

How to make my recycler adapter retrieve messages sent to firebase database?

I cannot get the chats to display in the recycler adapter, I have already in firebase database and as well have attached firebase recycler adapter
I have tried some of the ways of getting the recycler adapter to display the chats but unable to display my adapter
private void DisplayReceiverInformation() {
receiverName.setText(messageReceiverName);
rootReference.child("Users").child(messageReceiverID).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
//retrieve from db
final String userName = dataSnapshot.child("fullName").getValue().toString();
final String profileImage = dataSnapshot.child("profileImage").getValue().toString();
//set values
receiverName.setText(userName);
Picasso.get().load(profileImage).placeholder(R.drawable.profile_image_placeholder).into(receiverProfileImage);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
\\\
//initialize the above variables
private void InitializeFields() {
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//connect chat custom bar to chat activity
ActionBar actionBar = getSupportActionBar();
Objects.requireNonNull(actionBar).setDisplayHomeAsUpEnabled(true);
actionBar.setDisplayShowCustomEnabled(true);
LayoutInflater layoutInflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View action_bar_view = layoutInflater.inflate(R.layout.chat_custom_toolbar, null);
actionBar.setCustomView(action_bar_view);
receiverName = findViewById(R.id.custom_profile_name);
receiverProfileImage = findViewById(R.id.custom_profile_image);
sendMessageButton = findViewById(R.id.send_message_button);
userMessageInput = findViewById(R.id.input_message);
// messageAdapter = new MessagesAdapter(ChatActivity.this,)
messageAdapter = new MessagesAdapter( messageList);
userMessagesList = (RecyclerView) findViewById(R.id.messages_list_of_users);
linearLayoutManager = new LinearLayoutManager(this);
userMessagesList.setHasFixedSize(true);
userMessagesList.setLayoutManager(linearLayoutManager);
userMessagesList.setAdapter(messageAdapter);
}
\\\
#Override
protected void onStart() {
super.onStart();
rootReference.child("Messages").child(messageSenderID).child(messageReceiverID)
.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
Messages messages = dataSnapshot.getValue(Messages.class);
messageList.add(messages);
messageAdapter.notifyDataSetChanged();
}
#Override
public void onChildChanged(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onChildRemoved(#NonNull DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
\\\
MessagesAdapter.java
package com.MwandoJrTechnologies.the_smart_parent.Chats;
public class MessagesAdapter extends RecyclerView.Adapter<MessagesAdapter.MessageViewHolder> {
private List<Messages> userMessagesList;
private FirebaseAuth mAuth;
private DatabaseReference usersDatabaseReference;
public MessagesAdapter(List<Messages> userMessagesList) {
this.userMessagesList = userMessagesList;
}
public class MessageViewHolder extends RecyclerView.ViewHolder {
public TextView senderMessageText;
public TextView receiverMessageText;
public CircleImageView receiverProfileImage;
public MessageViewHolder(#NonNull View itemView) {
super(itemView);
senderMessageText = (TextView) itemView.findViewById(R.id.sender_message_text_view);
receiverMessageText = (TextView) itemView.findViewById(R.id.receiver_message_text_view);
receiverProfileImage = (CircleImageView) itemView.findViewById(R.id.receiver_message_profile_image);
}
}
#NonNull
#Override
public MessageViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.message_layout_of_users, parent, false);
mAuth = FirebaseAuth.getInstance();
return new MessageViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull MessageViewHolder holder, int position) {
//get senders ID
String messageSenderID = mAuth.getCurrentUser().getUid();
Messages messages = userMessagesList.get(position);
//get ID of the receiver
String fromUserID = messages.getFrom();
//now get type of message whether text or image
String fromMessageType = messages.getType();
//retrieve receivers profile image
usersDatabaseReference = FirebaseDatabase.getInstance().getReference().child("Users").child(fromUserID);
usersDatabaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.hasChild("profileImage")){
String receiverImage = dataSnapshot.child("profileImage").getValue().toString();
Picasso.get().load(receiverImage).placeholder(R.drawable.profile_image_placeholder)
.into(holder.receiverProfileImage);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
if (fromMessageType.equals("text")){
holder.receiverMessageText.setVisibility(View.INVISIBLE);
holder.receiverProfileImage.setVisibility(View.INVISIBLE);
//display the message to the sender and to the receiver
//for the receiver
if (fromUserID.equals(messageSenderID)) {
holder.senderMessageText.setBackgroundResource(R.drawable.sender_text_message_background);
holder.senderMessageText.setTextColor(Color.WHITE);
holder.senderMessageText.setGravity(Gravity.LEFT);
holder.senderMessageText.setText(messages.getMessage());
//for receiver
} else {
holder.senderMessageText.setVisibility(View.INVISIBLE);
holder.receiverMessageText.setVisibility(View.VISIBLE);
holder.receiverProfileImage.setVisibility(View.VISIBLE);
holder.receiverMessageText.setBackgroundResource(R.drawable.receiver_text_message_background);
holder.receiverMessageText.setTextColor(Color.WHITE);
holder.receiverMessageText.setGravity(Gravity.LEFT);
holder.receiverMessageText.setText(messages.getMessage());
}
}
}
#Override
public int getItemCount() {
return userMessagesList.size();
}
}
/// my modal class
Messages.java
package com.MwandoJrTechnologies.the_smart_parent.Chats;
//modal class to retrieve messages
public class Messages {
public String date, time, type, message, from;
public Messages(){
//empty default constructor
}
//generate constructor with parameters
public Messages(String date, String time, String type, String message, String from) {
this.date = date;
this.time = time;
this.type = type;
this.message = message;
this.from = from;
}
//generate getter and setter
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public String getFrom() {
return from;
}
public void setFrom(String from) {
this.from = from;
}
}
The above code does not give me any result in the FirebaseRecycler adapter yet I expect it to display in the FirebaseRecycler adapter

I think the answer is below.
private void DisplayReceiverInformation() {
receiverName.setText(messageReceiverName);
rootReference.child("Users").child(messageReceiverID).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
//retrieve from db
final String userName = dataSnapshot.child("fullName").getValue().toString();
final String profileImage = dataSnapshot.child("profileImage").getValue().toString();
//set values
receiverName.setText(userName);
Picasso.get().load(profileImage).placeholder(R.drawable.profile_image_placeholder).into(receiverProfileImage);
messageAdapter = new MessagesAdapter( messageList);
userMessagesList = (RecyclerView) findViewById(R.id.messages_list_of_users);
linearLayoutManager = new LinearLayoutManager(this);
userMessagesList.setHasFixedSize(true);
userMessagesList.setLayoutManager(linearLayoutManager);
userMessagesList.setAdapter(messageAdapter);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
//here the data will be null so you must display data inside onDataChange() method.
}

Can't convert object of type java.lang.String to type - Firebase

i want to build a Presense System with firebase but when i click join in toolbar, the app was forced stop.
com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.app.PresenseSystem.User
ListUsersActivity
public class ListUsersActivity extends AppCompatActivity {
DatabaseReference onlineRef, currentUserRef, counterRef;
private FirebaseFirestore firebaseFirestore;
FirebaseRecyclerAdapter<User, ListViewHolder> adapter;
RecyclerView ListOnline;
RecyclerView.LayoutManager layoutManager;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list_users);
ListOnline = (RecyclerView) findViewById(R.id.online_list);
ListOnline.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(this);
ListOnline.setLayoutManager(layoutManager);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
toolbar.setTitle("User lists");
setSupportActionBar(toolbar);
onlineRef = FirebaseDatabase.getInstance().getReference().child(".info/connected");
counterRef = FirebaseDatabase.getInstance().getReference("lastOnline");
currentUserRef = FirebaseDatabase.getInstance().getReference("lastOnline").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
Query QueryRef = counterRef.orderByKey();
setupSystem();
FirebaseRecyclerOptions Options = new FirebaseRecyclerOptions.Builder<User>().setQuery(QueryRef, User.class).build();
adapter = new FirebaseRecyclerAdapter<User, ListViewHolder>(Options) {
#Override
protected void onBindViewHolder(ListViewHolder holder, final int position, final User model) {
holder.setName(model.getEmail());
}
#Override
public ListViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.user_lists, parent, false);
return new ListViewHolder(view);
}
};
adapter.notifyDataSetChanged();
ListOnline.setAdapter(adapter);
}
private void setupSystem() {
onlineRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue(Boolean.class)) {
currentUserRef.onDisconnect().removeValue();
counterRef.child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.setValue(new User(FirebaseAuth.getInstance().getCurrentUser().getEmail(), "Online"));
adapter.notifyDataSetChanged();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
counterRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot postSnapshot:dataSnapshot.getChildren())
{
User user= postSnapshot.getValue(User.class);
Log.d("LOG",""+user.getEmail()+"is"+user.getStatus());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.main_menu,menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()){
case R.id.action_join:
counterRef.child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.setValue(FirebaseAuth.getInstance().getCurrentUser().getEmail(),"Online");
break;
case R.id.action_logout:
currentUserRef.removeValue();
}
return super.onOptionsItemSelected(item);
}
User
public class User {
public String name;
public String image;
public String email;
public String status;
public String userId;
public User(String email, String online) {
}
public User(String name, String image, String status, String email,String userid) {
this.name = name;
this.image = image;
this.status = status;
this.email= email;
this.userId=userid;
}
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
public String getEmail() {
return email;
}
public String getStatus() {
return status;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}}
ListViewHolder
public class ListViewHolder extends RecyclerView.ViewHolder {
private TextView UserName;
View mView;
public ListViewHolder(View itemView){
super(itemView);
mView = itemView;
}
public void setName(String Name){
TextView email = (TextView)mView.findViewById(R.id.text_email);
email.setText(Name);
}}

Please Change this
counterRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Here
for(DataSnapshot postSnapshot:dataSnapshot.getChildren())
{
User user= postSnapshot.getValue(User.class);
Log.d("LOG",""+user.getEmail()+"is"+user.getStatus());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
into
counterRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user= postSnapshot.getValue(User.class);
Log.d("LOG",""+user.getEmail()+"is"+user.getStatus());
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
and make sure that your User.class variables names and types matches the one on your firebase database