Firebase Android how to handle onChildAdded

Question

How to handle onChildAdded event in firebase android. below is my database json structure

 {
    message{
            "id"=10;
            "name"="xyz"
           }
 }

    public void onChildAdded(DataSnapshot dataSnapshot, String s) {

           // how can I handle the particular child that has added
        }

this method triggers when a new child is added to my reference node. But how can I get the value for the particular child with out typecasting

Answer 1

The child added is the one returned on the dataSnapshot. So, if you want to get it's key:

String myKey = dataSnapshot.getKey()

For the value:

String myKey = dataSnapshot.getValue(String.class)

For the value you need to define the type you are expecting. On this example I specified that a String is expected, but you can even cast the value to any object you are using (as long as the fields match on your object model and on the dataSnapshot):

User myUser = dataSnapshot.getValue(User.class)

For more details please go to the Firebase official documentation.

Answer 2

In reference, add your app firebase console url.

DatabaseReference myFirebaseRef = database.getReference("Your firbase path");
    myFirebaseRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        if(dataSnapshot.hasChild("message")) {
        for (DataSnapshot poly : dataSnapshot.child("message").getChildren()) {
            String id=String.valueOf(poly.child("id").getValue);
            String name=String.valueOf(poly.child("name").getValue);

        }
    }
         }
        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) 
         {

        }
        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

Answer 3

You will need a model class as per the child nodes and entities you have in your database.

public void onChildAdded(DataSnapshot dataSnapshot, String s) {

       ModelClass model = dataSnapshot.getValue(ModelClass.class)
       //assuming this is used for list of data..
       list.add(model);
}

Child Event Listener does not crash even if the child nodes are not available or not yet created dyanamically.You also won't need any loop for moving to the next node.

Answer 4

If you want to get just a specific child value then do this

  public void onChildAdded(DataSnapshot dataSnapshot, String s) {
           if(dataSnapshot.hasChild("name")){
              String name = dataSnapshot.child("name").getValue().toString();
           }
        }