如何使用 RxJava2 从 Twilio 聊天中获取所有分页频道？答案

【问题标题】：How to get all the paginated channels from Twilio chat using RxJava2?如何使用 RxJava2 从 Twilio 聊天中获取所有分页频道？
【发布时间】：2019-10-08 17:56:05
【问题描述】：

尝试使用 twilio SDK 从 Twilio 聊天中获取所有频道。想要等待频道列表加载（使用 Observables），然后在我的 UI 中显示它。以下是我正在尝试做的一个粗略的想法：


private List<Paginator<ChannelDescriptor> getAllChannels() {
  ChatClient.Properties props = new ChatClient.Properties.Builder()
        .createProperties();

  ChatClient chatClient = ChatClient.create(context.getApplicationContext(),
        accessToken,
        props,
        null);

  List<Paginator<ChannelDescriptor> channelList = new ArrayList<>()

  chatClient.getChannels().getUserChannelsList(new CallbackListener<Paginator<ChannelDescriptor>>() {
    @Override
    public void onSuccess(Paginator<ChannelDescriptor> firstPaginator) {
      channelList.add(firstPaginator);
      Paginator<ChannelDescriptor> nextPaginator = firstPaginator;

      while (nextPaginator != null && nextPaginator.hasNextPage()) {
            nextPaginator = loadNextChatChannelPage(firstPaginator);
            if(nextPaginator != null) {
              channelList.add(nextPaginator);
            }
      }
    }
  });

  return channelList;
}


public Paginator<ChannelDescriptor> loadNextChatChannelPage(Paginator<ChannelDescriptor> paginator) {
    paginator.requestNextPage(new CallbackListener<Paginator<ChannelDescriptor>>() {
        @Override
        public void onSuccess(Paginator<ChannelDescriptor> channelDescriptorPaginator) {
            return channelDescriptorPaginator;
        }

        @Override
        public void onError(ErrorInfo errorInfo) {
            return null.
        }
    }));
}

【问题讨论】：

这里没有真正的问题。这管用吗？你有错误吗？有什么意想不到的事情发生吗？
感谢您的回答，问题是如何在 RXJava2 中完成所有这些工作，请在下面发布我的解决方案，以防有人发现它有用

标签： android twilio rx-java2 twilio-api

【解决方案1】：

我最终做的是：

/**
* Start loading the Twilio chat channel pages
*
* @return Single containing a list of all the chat channel pages
*/
public Single<List<Paginator<ChannelDescriptor>>> loadAllChatChannelPages(ChatClientManager chatClientManager) {
    return Single.create(emitter -> chatClientManager.getChatClient().getChannels().getUserChannelsList(new CallbackListener<Paginator<ChannelDescriptor>>() {
        @Override
        public void onSuccess(Paginator<ChannelDescriptor> channelDescriptorPaginator) {
            if(channelDescriptorPaginator != null) {
                emitter.onSuccess(channelDescriptorPaginator);
            }
        }

        @Override
        public void onError(ErrorInfo errorInfo) {
            String errorMessage = "";
            if(errorInfo != null) {
                errorMessage = errorInfo.getMessage();
            }
            emitter.onError(new Throwable(errorMessage));
        }
    })).subscribeOn(Schedulers.io())
    .flatMap(firstPaginator -> {
        if(firstPaginator != null) {
            return loadChannelPaginator((Paginator<ChannelDescriptor>) firstPaginator).toList()
                    .subscribeOn(Schedulers.io());
        } else {
            return Single.error(new Throwable("Could not get chat channels"));
        }
    });
}

/**
 * Recursively loads the chat channel pages and returns them as a single observable
 *
 * @param paginator this needs to be the first chat channel paginator from the chat client
 * @return Observable containing a flattened version of all the available chat channel paginators
 */
private Observable<Paginator<ChannelDescriptor>> loadChannelPaginator(Paginator<ChannelDescriptor> paginator) {
    if (paginator.hasNextPage()) {
        return Observable.mergeDelayError(
            Observable.just(paginator),
            loadNextChatChannelPage(paginator)
                .flatMap(this::loadChannelPaginator));
    }

    return Observable.just(paginator);
}

/**
 * Loads a single chat channel page
 *
 * @param previousPage the previous page of chat channels
 * @return Observable containing the next chat channel page
 */
private Observable<Paginator<ChannelDescriptor>> loadNextChatChannelPage(Paginator<ChannelDescriptor> previousPage) {
    return Observable.create(emitter -> previousPage.requestNextPage(new CallbackListener<Paginator<ChannelDescriptor>>() {
        @Override
        public void onSuccess(Paginator<ChannelDescriptor> channelDescriptorPaginator) {
            if(channelDescriptorPaginator != null) {
                emitter.onNext(channelDescriptorPaginator);
            }
            emitter.onComplete();
        }

        @Override
        public void onError(ErrorInfo errorInfo) {
            if(errorInfo != null) {
                String errorMessage = errorInfo.getMessage();
                Timber.e(errorMessage);
            }
//                emitter.onError(new Throwable(errorMessage));
            emitter.onComplete();
        }
    }));
}

在上面的代码中，loadAllChatChannelPages 加载了第一个分页器。

如果不为 null，则 loadChannelPaginator 接管并通过执行 loadNextChatChannelPage 递归抓取每个下一个分页器，该方法为每个单独的分页器返回一个 observable。

然后 mergeDelayError 将所有分页器展平并将它们作为一个单独的 Observable 返回。

最后在 getAllChannels 中我应用 Observable.toList()，这将返回一个包含我需要的分页聊天频道列表的 Single。

【讨论】：