如果需要将发送的图片消息中的图片传到自己的服务器，需要调用下面接口发送图片消息， appUpload:(BOOL)appUpload传入YES。
- (void)sendMediaMessage:(RCMessageContent *)messageContent
pushContent:(NSString *)pushContent
appUpload:(BOOL)appUpload;
重写下面方法，异步线程模拟了一个上传的过程，使用时请替换为自己上传图片的过程，当图片上传成功后得到图片的URL地址，将这个地址赋值给图片消息中的imageUrl属性，然后将图片消息对象传给uploadListener.successBlock()即可。
- (void)uploadMedia:(RCMessage *)message uploadListener:(RCUploadMediaStatusListener *)uploadListener {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
int i = 0;
for (i = 0; i < 100; i++) {
uploadListener.updateBlock(i);
[NSThread sleepForTimeInterval:0.2];
}
RCImageMessage *imageMsg = (RCImageMessage*)message.content;
imageMsg.imageUrl = @“http://www.rongcloud.cn/images/newVersion/bannerInner.png?0717”;
uploadListener.successBlock(imageMsg);
});
}