RxJava改造轮询

Question

我的问题是我无法使用Retrofit获得无限流。在我获得初始轮询（）请求的凭据后-我执行初始轮询（）请求。如果没有变化，每个轮询（）请求会在25秒内响应，如果有任何变化，则会更早响应-返回changed_data[]。每个响应都包含下一个轮询请求所需的时间戳数据-我应该在每次轮询（）响应后执行新轮询（）请求。这是我的代码：

getServerApi().getLongPollServer() 
  .flatMap(longPollServer -> getLongPollServerApi(longPollServer.getServer()).poll("a_check", Config.LONG_POLLING_SERVER_TIMEOUT, 2, longPollServer.getKey(), longPollServer.getTs(), "") 
   .take(1) 
   .flatMap(longPollEnvelope -> getLongPollServerApi(longPollServer.getServer()).poll("a_check", Config.LONG_POLLING_SERVER_TIMEOUT, 2, longPollServer.getKey(), longPollEnvelope.getTs(), ""))) 
   .retry()
   .subscribe(longPollEnvelope1 -> {
   processUpdates(longPollEnvelope1.getUpdates());
});

我是RxJava新手，也许我不懂一些东西，但我无法获得无限流。我接到3个电话，然后是onNext和onComplete。

附言：也许有更好的解决方案在Android上实施长轮询？

Answer 1

虽然不理想，但我相信您可以使用RX的副作用来实现预期的结果（“doOn”操作）。

Observable<CredentialsWithTimestamp> credentialsProvider = Observable.just(new CredentialsWithTimestamp("credentials", 1434873025320L)); // replace with your implementation

Observable<ServerResponse> o = credentialsProvider.flatMap(credentialsWithTimestamp -> {
    // side effect variable
    AtomicLong timestamp = new AtomicLong(credentialsWithTimestamp.timestamp); // computational steering (inc. initial value)
    return Observable.just(credentialsWithTimestamp.credentials) // same credentials are reused for each request - if invalid / onError, the later retry() will be called for new credentials
            .flatMap(credentials -> api.query("request", credentials, timestamp.get()))  // this will use the value from previous doOnNext
            .doOnNext(serverResponse -> timestamp.set(serverResponse.getTimestamp()))
            .repeat();
})
        .retry()
        .share();

private static class CredentialsWithTimestamp {

    public final String credentials;
    public final long timestamp; // I assume this is necessary for you from the first request

    public CredentialsWithTimestamp(String credentials, long timestamp) {
        this.credentials = credentials;
        this.timestamp = timestamp;
    }
}

订阅“o”时，内部可观察将重复。如果有错误，那么“o”将重试并重新从凭据流请求。

在您的示例中，计算指导是通过更新timestamp变量来实现的，这对于下一个请求是必要的。