Firebase updatechildren vs setvalue

Question

I'm having a problem with valueEvenListener on Firebase. Consider the situation:

Firebase ref = new Firebase(Constant.BASEURL).child("myLists");
ref.addValueEventListener(myValueEventListener);

Then I try do update one of the lists value using updateChildren().

HashMap<String, Object> newEditionTimeHM = new HasMap<String, Object>
newEditionTimeHM.put("editionTimeStamp", ServerValue.TIMESTAMP);

ref.child(pushKey).updateChildren(newEditionTimeHM);

It updates but when my listener catches the update, it crashes reporting "failed to bounce to type" error.

On my second try, I create a new shoppinList object with the new values I want and push it using setValue().

newEditionTimeHM.put("editionTimeStamp", ServerValue.TIMESTAMP);
ShoppingList shoppingList = new ShoppingList("Owner unknown", newEditionTimeHM);

ref.child(pushKey).setValue(shoppingList);

When my listeners catches it, no problem is reported.

What is the difference here? Why do I need to create an entirely new object to satisfy the listener? Isn't it more efficient to use updateChildren()? Searched this page for the answer but did not find it.

Answer 1

ServerValue.TIMESTAMP has the type is Map<String, String>, so I guess your data structure in Firebase is related to this if your pushKey is "<your Firebase URL>/myLists":

"myLists": {
    "editionTimeStamp": {
        "timeStampKey": "timeStampValue"
    }
}

So, if you want to get TIMESTAMP value, i suggest your first try must be:

ref.child("<your Firebase URL>/myLists/editionTimeStamp/timeStampKey");
ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snapshot) {
        String timeStampValue = (String)snapshot.getValue();
    }
    @Override
    public void onCancelled(FirebaseError firebaseError) {
        System.out.println("The read failed: " + firebaseError.getMessage());
    }
});

If it's not your solution, here is a good explanation about this error: Why do I get "Failed to bounce to type" when I turn JSON from Firebase into Java objects?
Hope it help :D