如何使用 RxJava 2 发出 HTTP 请求以检查内容类型?

问题描述

我需要从特定 URL 获取内容类型.我知道我们可以通过简单的编码来实现:

I need to get the content type from a specific URL. I know that we can do it by simply coding:

URL url = new URL("https://someurl.com");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("HEAD"); // Request Method: GET/POST/UPDATE...
connection.connect();
String contentType = connection.getContentType();

既然这会阻塞 UI 线程(同步操作)，那么如何在 Android 上使用 RxJava 2 发出 HTTP 请求?

Since this blocks the UI thread (a synchronous operation), how to make a HTTP request using RxJava 2 on Android?

注意事项:

• 我不想使用 AsyncTask 来实现这一点.为什么?
• 这与 RxJava 2 而不是版本 1 相关.
• 如果可以，请给我一个清晰、简单和简洁的示例.

推荐答案

使用 RxJava just operator 离开主线程并从计算调度器继续线程上的进程，然后使用 flatMap 进行 http 调用并查找内容类型，网络调用应该在 IO 调度器的线程上运行，最后在主线程上观察并订阅结果.

Use RxJava just operator to leave main thread and continue the process on thread from computation scheduler and then use flatMap to make http call and find content type, network calls should run on threads from IO scheduler and finally observe on main thread and subscribe to result.

Observable.just(1).subscribeOn(Schedulers.computation())
       .flatMap(dummyValueOne -> {
          return Observable.just(getContentType).subscribeOn(Schedulers.io()); 
       }).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<String>() {
                    @Override
                    public void accept(String contentType) throws Exception {
            //do nextsteps with contentType, you can even update UI here as it runs on main thread
                    }
                }, new Consumer<Throwable>() {
                    @Override
                    public void accept(Throwable throwable) throws Exception {
                        Log.e("GetContentType", "exception getting contentType", throwable);
                    }
                }));

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