Android Tutorial Firebase Realtimedatabase get a chat or content preview (filtering)

limitToFirst() 'Sets the maximum number of items to return from the beginning of the ordered list of results.
limitToLast() 'Sets the maximum number of items to return from the end of the ordered list of results.
startAt() 'Return items greater than or equal to the specified key or value depending on the order-by method chosen.
endAt() 'Return items less than or equal to the specified key or value depending on the order-by method chosen.
equalTo() 'Return items equal to the specified key or value depending on the order-by method chosen.

Sub Process_Globals
'it is better to add this in a Service
Public auth As FirebaseAuthEx
Public realtime As FirebaseDatabase
End Sub

Sub Globals

Dim getLastmsg As DatabaseReference

End Sub

Sub Activity_Create(FirstTime As Boolean)

'this is better in a service! auth.Initialize("auth")
realtime.Initialize("Realtime")
realtime.PersistenceEnabled = True

auth.signInAnonymously

getLastmsg.Initialize("lastmsg",realtime.getReference2("/rooms/" & "idOfTheRoom" & "/messages"),"idOfTheRoom")
        getLastmsg.LimitToLast(1).addChildEventListener 'LimitToLast returns the list from new to old with limit, in this case we want only the last, that's why we set it to "1".
     
        getLastmsg.keepSynced(True)

End Sub


Sub lastmsg_onChildAdded(Snapshot As Object, child As String, tag As Object)
 
    Dim snap As DataSnapshot = Snapshot
    Dim NewMessage As Map = snap.Value
 
    Main.SQL1.ExecNonQuery2("UPDATE chats SET lastmsg = ?, lastmsgtime = ? WHERE sessionid= ? ", Array As Object(NewMessage.Get("text"), NewMessage.Get("timestamp"),tag)) 'this is only a example how to store you the value to the local db, i use the SQLite.
     
        ulv_chats.RefreshContent 'for example refresh the list, to build the list new, with the new values, i use the Ultimate Listview from Informatix.
 
End Sub