smack presence问题

Roser#getPresence(String user) will return null if the contact has no presence information available. This could be because the contact is offline or you are not subscribed to their presence

 

If you are getting null when your contact is online then it will be (most likely) one of two things.

 

1: Either you are not subscribed to the other contacts Presence. In which case you will need to before you are allowed to track their Online/Offline status.

 

2: As AWenckus mentioned, it can sometimes take a moment for the information to be sent so if you are performing this operation as soon as you login the method may well return null.

 

Far better to add a RosterListener to your connection to listen out for Presence changes.

 

Presence presence = (Presence)packet;
Presence.Mode presenceMode = presence.getMode();

if(presenceMode == Presence.Mode.AVAILABLE) {
    // user is online and available
}

if(presenceMode == Presence.Mode.AWAY) {
    //user is away
}

take for example two users:User A,User B

User A wants to see when User B is online.

User A sends a SUBSCRIBE packet to User B

User B then decides whether or not to allow User A to see when they are online.

If they accept the subscription requests they send a SUBSCRIBED packet

If they reject the subscription request they send a UNSUBSCRIBED packet.

 

参考：http://www.igniterealtime.org/community/message/115077#115077

评论

2 楼 Blackbaby 2012-05-21  

qmzpanda 写道

hi,有个问题我想咨询你一下：
Roster在添加RosterListener 监听后，页面通过Xbosh协议发Presence，Rosterlistener的 presenceChange()方法会有延迟，有碰到过类似问题吗？

你是做web应用吧？我们之前用的strophe.js开发  没有遇到过哦

1 楼 qmzpanda 2012-05-19  

hi,有个问题我想咨询你一下：
Roster在添加RosterListener 监听后，页面通过Xbosh协议发Presence，Rosterlistener的 presenceChange()方法会有延迟，有碰到过类似问题吗？