问如何判断聊天消息的状态(已读/未读)？

EN

//message delivery
    XMPPMessageDeliveryReceipts* xmppMessageDeliveryRecipts = [[XMPPMessageDeliveryReceipts alloc] initWithDispatchQueue:dispatch_get_main_queue()];
//don't write this line as it will send auto receipts whenever message will be delivered
    //xmppMessageDeliveryRecipts.autoSendMessageDeliveryReceipts = YES;
    xmppMessageDeliveryRecipts.autoSendMessageDeliveryRequests = YES;
    [xmppMessageDeliveryRecipts activate:self.xmppStream];

//Save to your Message Entity 

NSMutableDictionary *m = [[NSMutableDictionary alloc] init];
[m setObject: message_body forKey:@"message_body"];
[m setObject:messageID forKey:@"message_id"];
[m setObject:@"yes" forKey:@"isOutgoing"];
[m setObject:dateString forKey:@"date"];
[m setObject:timeString forKey:@"time"];
[m setObject:[NSDate date] forKey:@"timeStamp"];
[m setObject:yourId forKey:@"from"];
[m setObject:toId forKey:@"to"];

if (!Is_InternetAvailable]) {
 [m setObject:unsent forKey:@"chatStatus"];
}
else{
 [m setObject:sent forKey:@"chatStatus"];
}
[[CoreDataMethods sharedCoreDataMethods] saveUserMessage:m];
}

if ([message isoutGoing]) {//If I have sent the message

        // Mine bubble
        if ([[messageDict valueForKey:@"chatStatus"] isEqualToString:unsent]) {
            //set unsent image
        }
        else if ([[messageDict valueForKey:@"chatStatus"] isEqualToString:sent]){
            //set sent image
        }
        else if ([[messageDict valueForKey:@"chatStatus"] isEqualToString:received]){
          //set Received Image
        }
    }
    else{
        // Other Bubble , Notify them that you have read the message if it is unread/new message

        if ([[messageDict valueForKey:@"chatStatus"] isEqualToString:unread]) {

            //send read receipt
                NSXMLElement *receivedelement = [NSXMLElement elementWithName:@"received" xmlns:@"urn:xmpp:receipts"];

                NSXMLElement *message = [NSXMLElement elementWithName:@"message" xmlns:@"jabber:client"];
                [message addAttributeWithName:@"to" stringValue:toId];
                [message addAttributeWithName:@"from" stringValue:fromID];
                [receivedelement addAttributeWithName:@"id" stringValue:[messageDict valueForKey:@"message_id"]];
                [message addChild:receivedelement];

                //XMPPMessage *generatedReceiptResponse = [[messageDict valueForKey:@"xmppMessage"] generateReceiptResponse];
                [[[kAppDelegate xmppHandler] xmppStream] sendElement:message];

                // update message entity
                [self updateChatStatus:read withMessageID:[messageDict valueForKey:@"message_id"]];
        }
    }

- (void)xmppStream:(XMPPStream *)sender didReceiveMessage:(XMPPMessage *)message{

if ([message hasReceiptResponse]) {//message read
//Update database message entity
 [self updateChatStatus:@"received" withMessageID:[message receiptResponseID]];
}
}