以下是使用aSmack进行自定义扩展的完整解决方案：

首先我必须创建PacketExtension：

public class ExtensionFile implements PacketExtension {

public static final String ELEMENT = "file";

public static final String NAMESPACE = "file:namespace";

private String fileURL;

private String fileSize;

@Override

public String getElementName() {

return ELEMENT;

}

@Override

public String getNamespace() {

return NAMESPACE;

}

@Override

public String toXML() {

StringBuilder builder = new StringBuilder();

builder.append("

+ "\">");

if (fileURL != null) {

builder.append("").append(fileURL).append("");

}

if (fileSize != null) {

builder.append("").append(fileSize).append("");

}

builder.append("" + getElementName() + ">");

return builder.toString();

}

public void setFileURL(String fileURL) {

this.fileURL = fileURL;

}

public String getFileURL() {

return fileURL;

}

public void setFileSize(String fileSize) {

this.fileSize = fileSize;

}

public String getFileSize() {

return fileSize;

}

}

然后提供程序解析此数据包：

public class ExtensionProviderFile implements PacketExtensionProvider {

@Override

public PacketExtension parseExtension(XmlPullParser parser)

throws Exception {

ExtensionFile fileExt = new ExtensionFile();

int eventType = parser.next();

while (eventType == XmlPullParser.START_TAG) {

String name = parser.getName();

switch (parser.getEventType()) {

case XmlPullParser.START_TAG:

if (name.equals("fileURL")) {

fileExt.setFileURL(parser.nextText());

} else if (name.equals("fileSize")) {

fileExt.setFileSize(parser.nextText());

}

}

eventType = parser.next();

}

return fileExt;

}

}

发送带有文件扩展名的消息：

private void sendMessage(String recipient, String message){

Message msg = new Message(recipient,Message.Type.chat);

msg.setBody(message);

//Create extension and set values

ExtensionFile fileExt = new ExtensionFile();

fileExt.setFileURL("http://www.example.com/upload_files/"+ abc.jpg);

fileExt.setFileSize(fileSize);

//add extension to message

msg.addExtension(fileExt);

//send message

xmppConnection.sendPacket(msg);

}

要接收此消息,请实现PacketListener并覆盖processPacket()：

@Override

public void processPacket(Packet packet) {

Message message = (Message) packet;

//Get extension from message

ExtensionFile extFile = (ExtensionFile) message

.getExtension("file:namespace");

if (extFile != null) {

//Get values from extension

String filePath = extFile.getFileURL();

String fileSize = extFile.getFileSize();

System.out.println("Message :" + message.getBody() + " File url:" + filePath + " File size:" + fileSize);

}

}

并在连接到xmpp服务器之前添加此提供：

ProviderManager.getInstance().addExtensionProvider(

ExtensionFile.ELEMENT, ExtensionFile.NAMESPACE,

new ExtensionProviderFile());