认识smack中的基本对象 - Presence对象

一 Presence对象介绍

与IQ一样，Presence也是继承自XMPP的基类Packet信息包，Presence主要有两个用途：1）告诉服务器所有客户端当前所处的状态，2）发出添加/删除好友请求；每个Presence信息包都有一个类型属性Presence.Type，如下：

• available: 表示处于在线状态
• unavailable: 表示处于离线状态
• subscribe: 表示发出添加好友的申请
• unsubscribe: 表示发出删除好友的申请
• unsubscribed: 表示拒绝添加对方为好友
• error: 表示presence信息报中包含了一个错误消息。

除了类型信息外，Presence还包含其他一些可选的属性：

• Status: 用于表示用户状态的自定义文本，例如：外出吃饭
• Priority: 一个表示发送者资源优先级的非负数（我尚未搞明白什么是发送者资源）
• Mode: 表示五种状态之一：在线(默认）、聊天、离开、xa (extended away)、请勿打扰

二 用法示例

下面的示例表示向服务器发送一个邀请加入好友的Presence信息包的代码段：

Presence subscription = new Presence(Presence.Type.subscribe);subscription.setTo(packet.getFrom());ConnectionUtils.getConnection().sendPacket(subscription);

三 方法汇总

isAvailable

public boolean isAvailable()

如果用户在线，返回true,反之，返回false；另外，如果对方的presence信息包中如果包含添加好友的申请，也会返回false。fai方法等价于getType()==Presence.Type.available。需要注意，当用户状态为在线时，其Presence信息包中的Mode属性值还是有可能为以下几种模式：离开（away）,extended away 或者请勿打扰（do not disturb）.

返回值：在线状态的布尔值

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isAway

public boolean isAway()

Returns true if the presence type is available and the presence mode is away,extended away, ordo not disturb. False will be returned when the type or mode is any other value, including when the presence type is unavailable (offline). This is a convenience method equivalent totype == Type.available && (mode == Mode.away || mode == Mode.xa || mode == Mode.dnd).

Returns:

true if the presence type is available and the presence mode is away, xa, or dnd.

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getType

public Presence.Type getType()

Returns the type of this presence packet.

Returns:

the type of the presence packet.

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setType

public void setType(Presence.Type type)

Sets the type of the presence packet.

Parameters:

type - the type of the presence packet.

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getStatus

public String getStatus()

Returns the status message of the presence update, ornull if there is not a status. The status is free-form text describing a user's presence (i.e., "gone to lunch").

Returns:

the status message.

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setStatus

public void setStatus(String status)

Sets the status message of the presence update. The status is free-form text describing a user's presence (i.e., "gone to lunch").

Parameters:

status - the status message.

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getPriority

public int getPriority()

Returns the priority of the presence, or Integer.MIN_VALUE if no priority has been set.

Returns:

the priority.

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setPriority

public void setPriority(int priority)

Sets the priority of the presence. The valid range is -128 through 128.

Parameters:

priority - the priority of the presence.

Throws:

IllegalArgumentException - if the priority is outside the valid range.

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getMode

public Presence.Mode getMode()

Returns the mode of the presence update, or null if the mode is not set. A null presence mode value is interpreted to be the same thing asPresence.Mode.available.

Returns:

the mode.

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setMode

public void setMode(Presence.Mode mode)

Sets the mode of the presence update. A null presence mode value is interpreted to be the same thing asPresence.Mode.available.

Parameters:

mode - the mode.

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setLanguage

public void setLanguage(String language)

Sets the xml:lang of this Presence.

Parameters:

language - the xml:lang of this Presence.

Since:

3.0.2

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toXML

public String toXML()

Description copied from class: Packet

Returns the packet as XML. Every concrete extension of Packet must implement this method. In addition to writing out packet-specific data, every sub-class should also write out the error and the extensions data if they are defined.

Specified by:

toXML in classPacket

Returns:

the XML format of the packet as a String.

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toString

public String toString()

Overrides:

toString in classObject