How to limit retrieve data on firebase realtime Android Studio

How to limit retrieve data on firebase realtime Android Studio - android

I want to ask about how to limit retrieve data in Android Firebase. Here is my code:
private void lookingforHelp(){
DatabaseReference dbref = FirebaseDatabase.getInstance().getReference("Locations");
dbref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot ds: dataSnapshot.getChildren()){
int limitUser = 0;
ModelUsersLocation mUserLoct = ds.getValue(ModelUsersLocation.class);
LatLng yourLatLng = new LatLng(latitude_user, longitude_user);
LatLng polisiLatLng = new LatLng(mUserLoct.getLatitude(), mUserLoct.getLongitude());
if (mUserLoct.getPengguna().equals("polisi")){
if (SphericalUtil.computeDistanceBetween(yourLatLng, polisiLatLng) < 700) {
if (limitUser <= 5){
if (mUserLoct.getJangkauan().isEmpty()) {
DatabaseReference dbref = FirebaseDatabase.getInstance().getReference("Locations").child(mUserLoct.getUser().getUid());
HashMap<String, Object> hashMap = new HashMap<>();
hashMap.put("jangkauan", fuser.getUid());
dbref.updateChildren(hashMap).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
writeNewOrder();
}
});
}
}
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
I tried to retrieve data that i want is only less than 5 users, using int limitUser = 0; and it's still not working to retrieve data only less than 5 users.
PROBLEM SOLVED, I try to create markeroptions and make it into invisible, and then add it into arraylist, if (markers.size() <= 5) {do something}
thank u guys for your help btw i really apreciate it :))

public MutableLiveData<ArrayList<Vendor>> getVendorsByLimit(int limit) {
ArrayList<Vendor> arrayList = new ArrayList<>();
Query query = FirebaseDatabase.getInstance().getReference().child("VENDOR_NODE").limitToLast(limit);
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.getChildrenCount() > 0) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
if (snapshot.getChildrenCount() > 0) {
//String value = (String) snapshot.getValue(); //Get all child data
//OR
//String singleValue = (String) snapshot.child("fullName").getValue(); //Get single child data
Vendor model = snapshot.getValue(Vendor.class);
String key = snapshot.getKey();
arrayList.add(model);
}
}
data.setValue(arrayList);
} else {
data.setValue(null);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.e(TAG, "" + databaseError.getMessage());
data.setValue(null);
}
});
}
Query query = FirebaseDatabase.getInstance().getReference().child("VENDOR_NODE").limitToLast(limit);
You can sort them by using timeStamp like
-----------------------------------------
FirebaseDatabase.getInstance().getReference()
.child("Conversation").child(conversationID)
.limitToLast(100)
.orderByChild("timestamp")
.startAt(dateToStart) // pass timestamp from when you want to start filtering
.endAt(dateToEnd); // pass timestamp till when you want to apply filtering

Related

How to read data from RecyclerView and make comparison?

Hi I want to read the display data from RecyclerView and make comparison.
This my layout for the activity:
What I want to do is to read all data from RecyclerView and compare with Daily Calorie Suggestion.
After reading all data, I need to make comparisons on how many times the user have taken above, less or sufficient total calories as shown in the "Analysis of Total Calories Consumed of Last 7 Days"
The code:
#Override
protected void onStart() {
Query query = ref.orderByChild("timeStamp").limitToLast(7).endAt(Date);
super.onStart();
if (query != null) {
query .addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
userHighlights = new ArrayList<>();
for (DataSnapshot ds : dataSnapshot.getChildren()) {
userHighlights.add(ds.getValue(HighightsModel.class));
requiredCalorieRef = FirebaseDatabase.getInstance().getReference("Users").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
requiredCalorieRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String userCalorieSuggestion = String.valueOf((dataSnapshot.child("daily calorie").getValue()));
int daily_calorie = Integer.parseInt(userCalorieSuggestion);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
HighlightsAdapter highlightsAdapter = new HighlightsAdapter(userHighlights);
highlightsRV.setAdapter(highlightsAdapter);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(UserNewHighlights.this, databaseError.getMessage(),
Toast.LENGTH_SHORT).show();
}
});
}
}
This is my firebase:
Do I have to write a new code to solve this problem or else? Any help will be much appreciated. Thanks

As #MasoudDarzi mentioned, it's not related to the RecyclerView.
You can try something like this:
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
userHighlights = new ArrayList<>();
for (DataSnapshot ds : dataSnapshot.getChildren()) {
userHighlights.add(ds.getValue(HighightsModel.class));
requiredCalorieRef = FirebaseDatabase.getInstance().getReference("Users").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
requiredCalorieRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String userCalorieSuggestion = String.valueOf((dataSnapshot.child("daily calorie").getValue()));
int daily_calorie = Integer.parseInt(userCalorieSuggestion);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
HighlightsAdapter highlightsAdapter = new HighlightsAdapter(userHighlights);
highlightsRV.setAdapter(highlightsAdapter);
// do calculation here with userHighlights
int countExceeded = 0, countBelow = 0, countSufficient = 0;
for (HighightsModel h : userHighlights) {
if (h.totalCalorie > daily_calorie) {
countExceeded++;
} else if (h.totalCalorie < daily_calorie) {
countBelow++;
} else {
countSufficient++;
}
}
// update your TextView with the count numbers
// todo
}
}

so The brute force solution is to have a for in your data after getting the 7 days average.
for (your 7 days data){
// check if your data is lower or higher than the average
// and store number of higher or lower
}
looking for a better solution?

I have solved my problem by adding another child at History node. Whereby, previously I have only these for History :
but I add new child which is called STATUS, the status is updated from previous activity as seen the pic below:
so what I did for the code is :
private void upDateAnalysisAbove() {
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("History");
DatabaseReference mRef = ref.child(FirebaseAuth.getInstance().getCurrentUser().getUid());
Query mQuery = mRef.orderByChild("status").equalTo("ABOVE").limitToLast(7);
mQuery.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String value = String.valueOf(dataSnapshot.getChildrenCount());
int values = Integer.parseInt(value);
txt_above_output.setText(values + " times(s)");
upDateAnalysisLess(values);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
//LESS
private void upDateAnalysisLess(int values) {
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("History");
DatabaseReference mRef = ref.child(FirebaseAuth.getInstance().getCurrentUser().getUid());
Query mQuery = mRef.orderByChild("status").equalTo("LESS").limitToFirst(7);
mQuery.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String valueLess = String.valueOf(dataSnapshot.getChildrenCount());
int values_Less = Integer.parseInt(valueLess);
if (values_Less == 0){
txt_less_output.setText(values_Less + " times(s)");
}
if (values > values_Less){
int finalCount = values - values_Less ;
txt_less_output.setText(finalCount + " times(s)");
}
if (values <values_Less){
int finalCount = values_Less - values ;
txt_less_output.setText(finalCount + " times(s)");
}
updateSuff();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
//SUFFICIENT
private void updateSuff() {
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("History");
DatabaseReference mRef = ref.child(FirebaseAuth.getInstance().getCurrentUser().getUid());
Query mQuery = mRef.orderByChild("status").equalTo("SUFFICIENT").limitToFirst(7);
mQuery.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String value = String.valueOf(dataSnapshot.getChildrenCount());
int suffValue = Integer.parseInt(value);
if (suffValue == 0) {
txt_sufficient_output.setText(suffValue + " times(s)");
}
if (suffValue != 0){
txt_sufficient_output.setText(suffValue + " times(s)");
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Here is the output:
credit to this post that helped me a lot, and thanks for those who tried to help me.

Do calculation by retrieving data from Child Node is not working at all in Android Studio/Firebase

I have a problem to do subtract calculation by retrieving data from a Child Nod. As you can see my layout below, what I want to do is to get Remaining Kcal value by calculating Daily Kcal value minus Total Kcal and display the Remaining Kcal to the TextView.
I suspected the calculation for the subtraction part (code below) is not working at all as I tried to put the remainingCount/remainingCalorie value into firebase but nothing happened.
//CALCULATE AND DISPLAY REMAINING CALORIE
private void updateRemainingKcal(final double finalCount) {
DatabaseReference userRecord = FirebaseDatabase.getInstance().getReference();
DatabaseReference userReference = userRecord.child("Users").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
userReference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
double remainingCount = 0;
for (DataSnapshot userChild: dataSnapshot.getChildren()) {
for (DataSnapshot recordSnapshot: userChild.getChildren()) {
double userCalorie = Double.valueOf(recordSnapshot.child("daily calorie").getValue(String.class));
remainingCount = userCalorie - finalCount;
userRemainingCalorie.setText((remainingCount +"kcal"));
myHistoryRef = FirebaseDatabase.getInstance().
getReference("History").child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.child(date_record).child("Total Calorie");
Map<String, Object> values = new HashMap<>();
values.put("remainingCalorie", remainingCount);
myHistoryRef.updateChildren(values).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
}
});
}
}
Log.d("TAG", remainingCount + "");
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
}
This is relevant code to do this operation, whereby I need to retrieve "daily calorie' from User first, then I can do the substraction daily calorie (Required Kcal) - total calorie consume (Total Kcal) = Remaining Calorie (Remaining Kcal):
//**********************DATABASE REFERENCE FOR USER REQUIRED CALORIE***************************//
requiredCalorieRef = FirebaseDatabase.getInstance().getReference("Users").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
requiredCalorieRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String userCalorieSuggestion = String.valueOf((dataSnapshot.child("daily calorie").getValue()));
userRequiredCalorie.setText((userCalorieSuggestion +"kcal"));
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
//CALCULATE AND DISPLAY TOTAL CALORIE ACCORDING TO DATE
private void updateTotalCalorie(final String date_n) {
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference nameRef = rootRef.child("UsersRecords").child(FirebaseAuth.getInstance().getCurrentUser().getUid()).child(date_record);
nameRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
double count = 0;
for (DataSnapshot foodTypeSnapshot: dataSnapshot.getChildren()) {
for (DataSnapshot recordSnapshot: foodTypeSnapshot.getChildren()) {
double foodCalorie = Double.valueOf(recordSnapshot.child("foodCalorie").getValue(String.class));
count = count + foodCalorie;
userTotalCalorie.setText((count +"kcal"));
myHistoryRef = FirebaseDatabase.getInstance().
getReference("History").child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.child(date_record).child("Total Calorie");
Map<String, Object> values = new HashMap<>();
values.put("totalCalorie", count);
values.put("Date Consume", date_n);
final double finalCount = count;
myHistoryRef.updateChildren(values).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
updateRemainingKcal(finalCount);
}
});
}
}
Log.d("TAG", count + "");
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
}
//CALCULATE AND DISPLAY REMAINING CALORIE
private void updateRemainingKcal(final double finalCount) {
DatabaseReference userRecord = FirebaseDatabase.getInstance().getReference();
DatabaseReference userReference = userRecord.child("Users").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
userReference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
double remainingCount = 0;
for (DataSnapshot userChild: dataSnapshot.getChildren()) {
for (DataSnapshot recordSnapshot: userChild.getChildren()) {
double userCalorie = Double.valueOf(recordSnapshot.child("daily calorie").getValue(String.class));
remainingCount = userCalorie - finalCount;
userRemainingCalorie.setText((remainingCount +"kcal"));
myHistoryRef = FirebaseDatabase.getInstance().
getReference("History").child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.child(date_record).child("Total Calorie");
Map<String, Object> values = new HashMap<>();
values.put("remainingCalorie", remainingCount);
myHistoryRef.updateChildren(values).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
}
});
}
}
Log.d("TAG", remainingCount + "");
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
}
This is my firebase looks like - there is no node of RemainingCalorie at all at History node:
How can I solve this issue despite knowing the problem. I have tried several ways but nothing could help to solve this code problem.

I have solved my own problem. Thank you, finally did it. This is right code for those who have same problem in future:
private void updateRemaining(final int finalCount) {
userDatabase = FirebaseDatabase.getInstance().getReference("Users").child(FirebaseAuth.getInstance().getCurrentUser().getUid());
userDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String user = String.valueOf((dataSnapshot.child("daily calorie").getValue()));
int dailyCalorie = Integer.parseInt(user);
int remainingCalorie = dailyCalorie-finalCount;
userRemainingCalorie.setText((remainingCalorie +"kcal"));
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
throw databaseError.toException();
}
});
}
this is the screen-shot

I am getting ConcurrentModificationException while creating a chat application

While displaying the recent chats fragment in the application I am fetching my chats from firebase and filtering out the chats by their receiverID and senderID in the chat object to display the recent chats.
The problem says ConcurrentModificationException in ArrayList and it looks like due to the complexity of searching id in the array it occurred, I need a solution to minimize this chat filteration complexity.
// private List<String> stringList; Declaration at top
stringList = new ArrayList<>();
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
databaseReference = FirebaseDatabase.getInstance().getReference("BaatCheet/Chats/");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
//userModelList.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
MessageModel messageModel = dataSnapshot1.getValue(MessageModel.class);
if (messageModel.getSender().equals(firebaseUser.getUid())){
stringList.add(messageModel.getReceiver());
}
if (messageModel.getReceiver().equals(firebaseUser.getUid())){
stringList.add(messageModel.getSender());
}
}
readChat();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
The read chat function
private void readChat() {
userModelList = new ArrayList<>();
databaseReference = FirebaseDatabase.getInstance().getReference("BaatCheet/Users/");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
userModelList.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
UserModel userModel = dataSnapshot1.getValue(UserModel.class);
for (String id: stringList){
if (userModel.getId().equals(id)){
if (userModelList.size() !=0){
for (UserModel userModel1 : userModelList){
if (!userModel.getId().equals(userModel1.getId())){
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // If the existing list don't have same value for sender and reciever
} // end of inner userModel
} else {
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // end of else
} // end of userModel id equals string id
} // end of String is loop
} // end of DataSnapshot loop
usersAdapter = new UsersAdapter(userModelList);
recyclerView.setAdapter(usersAdapter);
} // end of onDataChange
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}// end of readChat()
The results would be the recyclerView of recent chats containing the chats which contain messages either send by the sender or receiver to each other.

In the following snippet of code :
for (UserModel userModel1 : userModelList){
if (!userModel.getId().equals(userModel1.getId())){
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // If the existing list don't have same value for sender and reciever
} //
You are modifying userModelList while iterating through userModelList. This is not allowed and is the cause of ConcurrentModificationException.
There are few ways to simplify the logic, the simplest (albeit not the best) would be to convert this foreach loop into a simple for i loop.
for (int i = 0; i< userModelList.size(); i++) {
UserModel userModel1 = userModelList.get(i);
if (!userModel.getId().equals(userModel1.getId())){
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // If the existing list don't have same value for sender and reciever
} //

Basically to handle this complexity I am now using separate nodes just for storing the chatLists as such now I don't need to read chats for filtering the recent chats.
The below code is for creating a new node everytime user sends a message it will update the node if the recieverID is different.
dbrefChatList = FirebaseDatabase.getInstance().
getReference("BaatCheet/ChatList/")
.child(senderuserID)
.child(receiveruserID);
dbrefChatList.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (!dataSnapshot.exists()){
dbrefChatList.child("id").setValue(receiveruserID);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
As such ChatList is a Model Class which contains single String called "id" and this id will be used to search in the node.
The below code is for the ChatFragment which fetches the chatList from firebase and set the data to recycler view.
// private List<ChatList> chatList; Declaration at top
chatListList = new ArrayList<>();
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
databaseReference = FirebaseDatabase
.getInstance()
.getReference("BaatCheet/ChatList")
.child(firebaseUser.getUid());
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
chatListList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()){
ChatList chatList = snapshot.getValue(ChatList.class);
chatListList.add(chatList);
}
myChatList();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
The function myChatList act as the function of readChat in the problem statement.
private void myChatList() {
userModelList = new ArrayList<>();
databaseReference = FirebaseDatabase.getInstance().getReference("BaatCheet/Users/");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
userModelList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()){
UserModel userModel = snapshot.getValue(UserModel.class);
for (ChatList chatList : chatListList){
if (userModel.getId().equals(chatList.getId())){
userModelList.add(userModel);
}
}
}
usersAdapter = new UsersAdapter(userModelList);
recyclerView.setAdapter(usersAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}

You can set a flag while traversing the array, after it's done, add it if it doesn't exist yet:
// Display 1 user from chats
for (String id : str_usersList) {
if (user.getId().equals(id)) {
if (userList.size() != 0) {
boolean exists = false;
// If not exists then add
for (User user1 : userList) {
if (user.getId().equals(user1.getId())) {
exists = true;
}
}
if (!exists) {
userList.add(user);
}
} else {
userList.add(user);
}
}
}

Android Firebase, Get position of key in node

I want to get data according to user's ranking. First order by user's points and get users position in node. But I can't think of the way to implement this.
First This is my firebase 'users' node
Maybe It will be like 'databaseRef.child("users").orderByChild("points")...'
I don't know from here.
ps. It's not get nth item. It's 'where is the item' ( item's nth )
Thank you!

This can be done by adding a ctr in you dataSnapshot loop
myRef = FirebaseDatabase.getInstance().getReference().child("users");
final Query query = myRef.orderByChild("points");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int total = dataSnapshot.getChildrenCount();
int i = 0;
// loop through dataSnapshot
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
String nickName = childSnapshot.child("nickName").getValue(String.class);
if (nickName.equals(mUser.getNickName()) {
//when nickName would match
int userPlace = total - i;
int points = childSnapshot.child("points").getValue(Interger.class);
//do something here
break;
} else {
i++;
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Kindly read
Retrieving Data.
How Data is Ordered
The callback function receives a DataSnapshot, which is a snapshot of
the data. A snapshot is a picture of the data at a particular database
reference at a single point in time. Calling val() / getValue() on a
snapshot returns the a language-specific object representation of the
data. If no data exists at the reference's location, the snapshot's
value is null.
If you want to get all points then check this LOGIC.
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("products");
ref.addListenerForSingleValueEvent(
new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
ArrayList<Integer> points = new ArrayList<>();
for (Map.Entry<String, Object> entry : products.entrySet()){
Map singleUser = (Map) entry.getValue();
points.add((Integer) singleUser.get("points"));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
//handle databaseError
}
});

I solve this problem. Android_K.Doe's answer is right. I add some code in his code. Because Firebase database does not give descending query.
final Query query = databaseReference.child("users").orderByChild("points");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int i = 0;
int all = (int) dataSnapshot.getChildrenCount();
Log.d(TAG, "all: " + all);
for (DataSnapshot ds : dataSnapshot.getChildren()) {
String nickName = ds.child("nickName").getValue(String.class);
if (nickName.equals(user.getNickName())) {
Log.d(TAG, "nickName: " + user.getNickName());
int userPlace = i;
Log.d(TAG, "position: " + userPlace);
myInfoRankingNumTxt.setText(Integer.toString(all - (i)) + "위");
break;
} else {
i++;
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Need help regarding a firebase Query to append the values of a key from multiple nodes of the same child

I want to retrieve the value for each category and then add it to the MPAndroid Pie Chart module that I'm using.
Basically, I want to:
Get value for Communication from month 1
Get value for Communication from month 2
Add the values
Add it to my List Cats with Cats.add(new PieEntry(my_total_value,category_name);
This is what I'm currently implementing for my radar chart but it duplicates each category for each month because it adds a value to the list for each month:
public void setYearRadar(final String date, boolean incexp)
{
final String incexpt;
if(incexp)
{
incexpt="Expense";
}
else
{
incexpt="Income";
}
final DatabaseReference dRef = FirebaseDatabase.getInstance().getReference();
dRef.child("Users")
.child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.child(date)
.addListenerForSingleValueEvent(new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
Rcats = new ArrayList<>();
Rlabel = new ArrayList<>();
for (DataSnapshot d: dataSnapshot.getChildren())
{
Query expQuery =
dRef.child("Users")
.child(cAuth.getCurrentUser().getUid())
.child(date)
.child(d.getKey())
.child("Transactions")
.child("Category")
.child(incexpt);
if(expQuery!=null)
{
expQuery.addListenerForSingleValueEvent(new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
Float x=0f;
for (DataSnapshot d : dataSnapshot.getChildren())
{
x = x + Float.parseFloat(d.getValue().toString());
}
for (DataSnapshot d : dataSnapshot.getChildren())
{
if (Float.parseFloat(d.getValue().toString()) > 0.0)
{
Rcats.add(new RadarEntry(Float.parseFloat(d.getValue().toString())/x*100, d.getKey())); //Adding value and converting to percentage
Rlabel.add(d.getKey());
}
}
if (!Rcats.isEmpty()&& Rcats.size()>2 && Rlabel.size()>2)
{
initRadarChart(Rcats,Rlabel,date,incexpt);
}
else
{
rc.setVisibility(LinearLayout.GONE);
}
}
#Override
public void onCancelled(DatabaseError databaseError)
{
}
});
}
}
}
#Override
public void onCancelled(DatabaseError databaseError)
{
}
});
}
This is how my Categories look like
This is my whole data structure
And here is the even more messy PieChart class
private void setYearPie(final String date, Boolean incexp)
{
final String incexpt;
if(incexp)
{
incexpt="Expense";
}
else
{
incexpt="Income";
}
final DatabaseReference dRef = FirebaseDatabase.getInstance().getReference();
dRef.child("Users")
.child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.child(date)
.addListenerForSingleValueEvent(new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
Ycats = new ArrayList<>();
Ylabel = new ArrayList<>();
for (DataSnapshot d: dataSnapshot.getChildren())
{
Query expQuery =
dRef.child("Users")
.child(cAuth.getCurrentUser().getUid())
.child(date)
.child(d.getKey())
.child("Transactions")
.child("Category")
.child(incexpt);
if(expQuery!=null)
{
expQuery.addListenerForSingleValueEvent(new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
for (DataSnapshot d : dataSnapshot.getChildren())
{
if (Float.parseFloat(d.getValue().toString()) > 0.0)
{
Ycats.add(new PieEntry(Float.parseFloat(d.getValue().toString()), d.getKey()));
Ylabel.add(d.getKey());
x = 0f;
}
if (!Ycats.isEmpty())
{
initPieChart(Ycats,Ylabel,date,incexpt);
}
else
{
//pc.setVisibility(LinearLayout.GONE);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError)
{
}
});
}
}
}
#Override
public void onCancelled(DatabaseError databaseError)
{
}
});
}
My expected outcome is that I want to create the final list for each category entered once with values from each month for that category, Eg. if in month 1 food=400 and in month 2 food=800 then I want my final list added as {1200,food}
I'm at my wits end here, and my brain has stopped working, I'd really appreciate any help, thanks.

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