使用 RxJava 处理分页 [英] Handle Paging with RxJava

问题描述

我在 Android 应用程序上使用 Retrofit + RxJava，并问自己如何处理 API 分页以链接调用，直到检索到所有数据.是这样的:

I'm using Retrofit + RxJava on an Android app and am asking myself about how to handle the API pagination to chain calls until all data is being retrieved. Is something like this:

Observable<ApiResponse> getResults(@Query("page") int page);

ApiResponse 对象具有简单的结构:

The ApiResponse object has a simple structure:

class ApiResponse {
    int current;
    Integer next;
    List<ResponseObject> results;
}

API 将返回 next 值直到最后一页.

The API will return a next value until is last page.

有什么好的方法可以实现这一目标吗?尝试结合一些 flatMaps()，但没有成功.

There's some good way to achieve this? Tried to combine some flatMaps(), but had no success.

推荐答案

您可以递归建模:

Observable<ApiResponse> getPageAndNext(int page) {
  return getResults(page)
      .concatMap(new Func1<ApiResponse, Observable<ApiResponse>>() {

        @Override
        public Observable<ApiResponse> call(ApiResponse response) {
          // Terminal case.
          if (response.next == null) {
            return Observable.just(response);
          }
          return Observable.just(response)
              .concatWith(getPageAndNext(response.next));
        }

      });
}

然后，消费它，

getPageAndNext(0)
    .concatMap(new Func1<ApiResponse, Observable<ResponseObject>>() {

        @Override
        public Observable<ResponseObject> call(ApiResponse response) {
          return Observable.from(response.results);
        }

    })
    .subscribe(new Action1<ResponseObject>() { /** Do something with it */ });

这应该会为您提供一个 ResponseObject 流，它将按顺序到达，并且很可能以页面大小的块的形式到达.

That should get you a stream of ResponseObject that will arrive in order, and most likely arrive in page-size chunks.

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