Spark研究笔记9：重要的工厂类PresenceManager（原创）

PresenceManager用于用户的在线状态和模式处理，类 Presence 位于org.jivesoftware.smack.packet，说明：

public enum Type {

       /**
        * The user is available to receive messages (default).
        */
        available,

        /**
         * The user is unavailable to receive messages.
         */
        unavailable,

        /**
         * Request subscription to recipient's presence.
         */
        subscribe,

        /**
         * Grant subscription to sender's presence.
         */
        subscribed,

        /**
         * Request removal of subscription to sender's presence.
         */
        unsubscribe,

        /**
         * Grant removal of subscription to sender's presence.
         */
        unsubscribed,

        /**
         * The presence packet contains an error message.
         */
        error
    }

    /**
     * An enum to represent the presence mode.
     */
    public enum Mode {

        /**
         * Free to chat.
         */
        chat,

        /**
         * Available (the default).
         */
        available,

        /**
         * Away.
         */
        away,

        /**
         * Away for an extended period of time.
         */
        xa,

        /**
         * Do not disturb.
         */
        dnd
    }

/**
     * Returns true if the user is online.
     *
     * @param jid the jid of the user.
     * @return true if online.
     */
    public static boolean isOnline(String jid) {
        final Roster roster = SparkManager.getConnection().getRoster();
        Presence presence = roster.getPresence(jid);
        return presence.isAvailable();
    }

    /**
     * Returns true if the user is online and their status is available or free to chat.
     *
     * @param jid the jid of the user.
     * @return true if the user is online and available.
     */
    public static boolean isAvailable(String jid) {
        final Roster roster = SparkManager.getConnection().getRoster();
        Presence presence = roster.getPresence(jid);
        return presence.isAvailable() && !presence.isAway();
    }

    /**
     * Returns true if the user is online and their mode is available or free to chat.
     *
     * @param presence the users presence.
     * @return true if the user is online and their mode is available or free to chat.
     */
    public static boolean isAvailable(Presence presence) {
        return presence.isAvailable() && !presence.isAway();
    }

    /**
     * 返回用户状态
     *
     * @param jid the users jid.
     * @return the users presence.
     */
    public static Presence getPresence(String jid) {
        final Roster roster = SparkManager.getConnection().getRoster();
        return roster.getPresence(jid);
    }

    /**
     * JID完整全称，例如(ex. derek@jivesoftware.com --> derek@jivesoftware.com/spark)
     */
    public static String getFullyQualifiedJID(String jid) {
        final Roster roster = SparkManager.getConnection().getRoster();
        Presence presence = roster.getPresence(jid);
        return presence.getFrom();
    }