roster.addSubscribeListener() can't receive the Type.Subscribe sometimes

[Klee]

i am using Smack 4.4.8

i try to use UserA to send a Presence.Type.Subscribe packet by roster.createItemAndRequestSubscription to UserB who is offline.

If I write the code like this：

        Roster roster = Roster.getInstanceFor(connection);

        roster.setSubscriptionMode(Roster.SubscriptionMode.manual);

        System.out.println(roster.getSubscriptionMode());

        roster.addSubscribeListener(new SubscribeListener() {
            @Override
            public SubscribeAnswer processSubscribe(Jid from, Presence subscribeRequest) {
                System.out.println(subscribeRequest.toXML());
                return null;
            }
        });

When UserB online , he will receive the packet from UserA.

But if i change the postion of the " roster.addSubscribeListener" like this:

        Roster roster = Roster.getInstanceFor(connection);

        roster.setSubscriptionMode(Roster.SubscriptionMode.manual);

        System.out.println(roster.getSubscriptionMode());
       <------------------------------------------------------------>
            other code
            other code
            other code
            other code
            other code
       <------------------------------------------------------------>

        roster.addSubscribeListener(new SubscribeListener() {
            @Override
            public SubscribeAnswer processSubscribe(Jid from, Presence subscribeRequest) {
                System.out.println(subscribeRequest.toXML());
                return null;
            }
        });

When UserB online ,he can’t receive the packet from UserA. Even packets from UserA will be deleted directly sometimes.

[Flow]

You don’t seem to invoke Roster.createItemAndRequestSubscription() in the two code snippets shown.