Smack getPrivacyList方法拋出classCastException

Question

我在基於XMPP的通信的Android應用程序中使用Smack。我正在嘗試使用PrivacyManager創建一個隱私列表。我已經成功創建了一個PrivacyList，但是當我嘗試訪問該列表時，它返回ClassCastException。下面是代碼：

PrivacyListManager privacyManager; 
privacyManager = PrivacyListManager.getInstanceFor(connection); 
PrivacyList privacyList = privacyManager.getPrivacyList("msg_block_list"); 

調查多一點，我已經發現，在調用getRequest方法發生異常在PrivacyListManager.java類上下面的行：

Privacy privacyAnswer = 
      (Privacy) response.nextResult(SmackConfiguration.getPacketReplyTimeout()); 

這裏是調用getRequest方法：

private Privacy getRequest(Privacy requestPrivacy) throws XMPPException { 
     // The request is a get iq type 
     requestPrivacy.setType(Privacy.Type.GET); 
     requestPrivacy.setFrom(this.getUser()); 

     // Filter packets looking for an answer from the server. 
     PacketFilter responseFilter = new PacketIDFilter(requestPrivacy.getPacketID()); 
     PacketCollector response = connection.createPacketCollector(responseFilter); 

     // Send create & join packet. 
     connection.sendPacket(requestPrivacy); 

     // Wait up to a certain number of seconds for a reply. 
     Privacy privacyAnswer = 
      (Privacy) response.nextResult(SmackConfiguration.getPacketReplyTimeout()); 

     // Stop queuing results 
     response.cancel(); 

     // Interprete the result and answer the privacy only if it is valid 
     if (privacyAnswer == null) { 
      throw new XMPPException("No response from server."); 
     } 
     else if (privacyAnswer.getError() != null) { 
      throw new XMPPException(privacyAnswer.getError()); 
     } 
     return privacyAnswer; 
    } 

我跟着this教程實現PrivacyList。任何人都可以幫忙

Answer 1

我發現了這個問題。 XML文件smack.providers缺失。我創建了具有以下內容的文件，它工作。

<?xml version="1.0"?> 
<!-- Providers file for default Smack extensions --> 
<smackProviders> 
<!-- Privacy --> 
    <iqProvider> 
     <elementName>query</elementName> 
     <namespace>jabber:iq:privacy</namespace> 
     <className>org.jivesoftware.smack.provider.PrivacyProvider</className> 
    </iqProvider>  
</smackProviders> 

Answer 2

PacketCollector'getResult()返回Packet對象，但它可能是從Packet類對象中的任何繼承，無論是Message或Presence或IQ S分析（在IQ情況下，你可以使用(privacy)投，因爲Privacy是IQ的子類）。在你的情況下，你似乎得到了另一個層次結構中存在的對象，而不是Privacy類。