Problem retrieve similar child element of firebase

Question

I want to retrieve only the date and all the date element at once and store them in array in the firebase as shown below.

i have used the following code to retrieve but failed to that.

    public void showData(View view) {

    final ArrayList<String> date = new ArrayList<>();
    firebaseDatabase = FirebaseDatabase.getInstance().getReference().child("Date");

    firebaseDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            date.add(dataSnapshot.getValue().toString());
            display.setText(dataSnapshot.getValue().toString());
        }

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

        }
    });
}

Please help to find a solution for this.

Answer 1

The firebase reference is wrong, you should go from the top node to the date node.

Change this:

firebaseDatabase = FirebaseDatabase.getInstance().getReference().child("Date");

into this:

firebaseDatabase = FirebaseDatabase.getInstance().getReference().child("Name");
 firebaseDatabase.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
       for(DataSnapshot datas: dataSnapshot.getChildren()){
        date.add(datas.child("Date").getValue().toString());
           }
    }

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

    }
});

Since you want to get all Date then put the firebase reference at the node Name and loop inside the names to be able to retrieve all the dates.

---

If you want to get the date of one user example Ravi , then you do not need to loop, you can do the following:

firebaseDatabase = FirebaseDatabase.getInstance().getReference().child("Name").child("Ravi").child("Date");

firebaseDatabase.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
    date.add(dataSnapshot.getValue().toString());
       }
}

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

    }
 });

Answer 2

As said by @PeterHaddad in the previous answer, the sequence to access the data you have taken is not right. You may try this way, if nothing else helped until yet.

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
rootRef.child("Names").orderByChild("Date").addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
       for(DataSnapshot ds: dataSnapshot.getChildren()){
        date.add(ds.getValue(String.class));
           }
    }

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

    }
});

//Also as you've told that code is not working, please tell, what exactly is not working