Fetch children data from Firebase Database in ListView

Question

I have a ListView. Within the list view, I want to fetch data from the Firebase database. I am able to show title, count in the activity. I want to fetch how many status shows unread and it will be semester Wise.

unread_count not working.

Below is the database structure:

I have tried below but unable to fetch unread_count. It always shows 0

    databaseReference = FirebaseDatabase.getInstance().getReference("All_Image_Uploads_Database");
    databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            list = new ArrayList<ListType>();
            list.clear();
            for (DataSnapshot postSnapshot:dataSnapshot.getChildren()){
                String count = String.valueOf(postSnapshot.getChildrenCount());
                String title = postSnapshot.getKey();
                String unread_count = String.valueOf(postSnapshot.child("status").getChildrenCount());
                ListType listType = new ListType(title, count, unread_count);
                list.add(listType);

            }

            ListTypeList listTypeList = new ListTypeList(HomeActivity.this, list);
            listView.setAdapter(listTypeList);
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

I need to fetch how many "status" shows "unread". It means to count the numbers of "unread" in semester wise.

I need your suggestion of how I will get the required data.

Answer 1

According to this comment:

"Semester I" : unread> 1, , "Semester II": unread> 3, "Semester III":unread> 2 likewise I need result. I want to get the result from all Semester

And this:

Semester is dynamic. How will I fetch the result, Plz suggest Sir

I can tell that you cannot count that in a single query. You have to use either a query for each semester separately and count them one by one or you can duplicate data. The best solution I can think of might be to change your database schema. Your new schema might look like this:

Firebase-root
   |
   --- allSemesters
         |
         --- -M7_k ... 8Agw
         |      |
         |      --- semester: 1
         |      |
         |      --- //Other data
         |
         --- -M7a1 ... zZoO
                |
                --- semester: 2
                |
                --- //Other data

Using a schema like this, you can solve two problems. One would be to get the count of all objects, and the second would be get the count of a particular semester. As you requested in your question, to count all those objects, please use the following lines of code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference allSemestersRef = rootRef.child("allSemesters");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Log.d("TAG", "Count: " + dataSnapshot.getChildrenCount());
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
    }
};
allSemestersRef.addListenerForSingleValueEvent(valueEventListener);

You can also take a look at my answer from the following post:

• Firebase gets slower when counting products from the database (Android)

If you only want to get the object of a particular semester, you should use the following query:

allSemestersRef.orderByChild("semerster").equalTo(2);