Firebase Childeventlistener Return Value When Path Does Not Exist

Reading the documentation, It seems childEventListener does not fire when the path does not exist. This is a problem since I want to display a message to the user that there is no

Solution 1:

If you want to handle both the children and the case where no children exists, you can add both a value and a child listener:

Query query = firebaseRef.child(users).child(userid).limitToLast(1);
query.addChildEventListener(newChildEventListener() {
    voidonChildAdded(DataSnapshot snapshot, String previousChildKey) {
        ...
    }
    ...
});
query.addValueEventListener(newValueEventListener() {
    voidonDataChange(DataSnapshot snapshot) {
        if (!snapshot.exists()) {
            // TODO: handle the "no data available" scenario
        }
    });
});

The Firebase client is smart enough to only load data once, even if there are multiple listeners like in the above case.

---

If you want, you can also accomplish this with a single ValueEventListener like this:

query.addValueEventListener(newValueEventListener() {
    voidonDataChange(DataSnapshot snapshot) {
        if (!snapshot.exists()) {
            // TODO: handle the "no data available" scenario
        }
        else {
            for (DataSnapshotchildSnapshot: snapshot.getChildren()) {
                // TODO: handle the child snapshot
            }
        }
    });
});

Since we now get all matching child nodes in snapshot, we loop over the snapshot.getChildren() to get the same data as in onChildAdded.

Solution 2:

Since its impossible to attach a listener to a non existing path, you could try adding a property to your user that sets the number of posts he has. Add a listener to that property and if it changes, then you are certain that indeed the user has a path reference in posts, then you can add a listener to that node and get the query every time a child is added with .childAdded .