hi, i'm not true if i find the solution.

I check the source code, decompile the smack.jar(with spark 2.5.8). I find that:

org.jivesoftware.smack.PacketReader has a field: listerners

protected final Map<PacketListener, ListenerWrapper> listeners = new ConcurrentHashMap<PacketListener, ListenerWrapper>();

the listerners is used to notify all packetListener.

for example:

1,org.jivesoftware.spark.filetransfer.SparkTransferManager{

......

private void addPresenceListener() {
        SparkManager.getConnection().addPacketListener(new PacketListener() {

           public void processPacket(Packet packet) {
                Presence presence = (Presence)packet;
                if (presence.isAvailable()) {

                    ......

}

......

2,org.jivesoftware.smack.Roster

   ......

        PacketFilter rosterFilter = new PacketTypeFilter(RosterPacket.class);
        connection.addPacketListener(new RosterPacketListener(), rosterFilter);
        PacketFilter presenceFilter = new PacketTypeFilter(Presence.class);
        presencePacketListener = new PresencePacketListener();
        connection.addPacketListener(presencePacketListener, presenceFilter);

  ......

Because listerners use Map, not List, so it's unordered. when spark starts up,  1 may been notified before 2. but next time, 2 may before 1.

if 1 before 2, the offline file transfer will get the message:The user is offline. Will auto-send "xxx" when user comes back online

So i change org.jivesoftware.smack.PacketReader,use a ordered Map (ConcurrentSkipListMap)

          protected final Map<PacketListener, ListenerWrapper> listeners =
            new java.util.concurrent.ConcurrentSkipListMap<PacketListener, ListenerWrapper>(new java.util.Comparator(){
             public int compare(Object o1, Object o2){
              return 1;
             }
             public boolean equals(Object obj) {
              return super.equals(obj);
             }
            });

compile, then put into smack.jar

I test this , it seem ok.

hehe, i'm not sure if this is the solution. I just want this to be helpful.