CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-database
Hanna
Hanna

Reputation: 11

How to retrieve list from firebase realtime database?

I am developing an Attendance App. I want to retrieve students list with number of presents and populate it in a list view.

I have tried the below code but i am getting number of presents of one specific student.

 DatabaseReference ref = 
 FirebaseDatabase.getInstance().getReference().child("Students 
 Attendance").child(selectedItem).child(id).child(subject);
 ref.addListenerForSingleValueEvent(new ValueEventListener() {
  @Override
  public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.getValue() != null) {

        Userlist.add(dataSnapshot.getValue().toString());
        addStudents(Userlist);
                      }else {
          Toast.makeText(getApplicationContext(), "****NO Record 
          FOUND****", Toast.LENGTH_LONG).show();
                      }
                  }

I expect the output as a list of students with their number of presents populated in list view.

My firebase Structure

I want this kind of result

Upvotes: 0

Views: 220

Answers (2)

Sagar Balyan
Sagar Balyan

Reputation: 658

Since you are making an app that counts a number of presents of a particular student. You can do it this way:

First you can set the value to be stored in the database as : mFirebaseDatabaseReference.push().setValue(new String[]{student_name,attendance})

This stores the data as :- Sam,70 and Mike,75

Now retrive that data using ChildEventListener:

mChildEventListener = new ChildEventListener() {
   @Override
   public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
     String data = dataSnapshot.getValue();
     mMyAdapter.add(data);
);

One thing to not here is that, you dont necessarily need to put the student_id as we using the push() method here so it gives every child a new id so that we don't have to worry about the data being disturbed for students with the same name or marks.

Upvotes: 1

Hanna
Hanna

Reputation: 11

     ref.addChildEventListener(new ChildEventListener() {
           @Override
           public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            if (dataSnapshot.exists()) {                      
             String value = dataSnapshot.getValue().toString();
             String key = dataSnapshot.getKey();
             String record = key + ":              " + value;
                        Userlist.add(record);
                        addStudents(Userlist);
         }

It worked for me.

Upvotes: 0

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