Convert list to another list using RxJava

Question

The need is a little strange. I want to convert a list to a new list. For example, convert List<Android> to List<AndroidWrapper>.

class AndroidWrapper has two fields.

public class AndroidWrapper {
    private Android mAndroid;
    private String mAvatarUrl;

    public AndroidWrapper(Android android, String avatarUrl) {
        this.mAndroid = android;
        this.mAvatarUrl = avatarUrl;
    }
}

The field mAvatar is related to mAndroid field and it can be fetched from remote server.

Observable<String> fetchAvatarUrl(Android android)

So how can do this using RxJava2?

akarnokd · Accepted Answer · 2018-03-07 12:12:04Z

2

Turn your list into an Observable, flatMap the dependent call onto it, create the final object type and collect it into a list:

Observable.fromIterable(androids)
.flatMap(android ->
     fetchAvatarUrl(android)
     // go into a backgroud thread
     .subscribeOn(Schedulers.io())
     // combine the result with the original value
     .map(url -> new AndroidWrapper(android, url))
     // limit the maximum concurrent fetch calls
     , 1
)
.toList();

answered Mar 7, 2018 at 12:12

akarnokd

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7 Comments

CoXier Over a year ago

Thanks very much. Since android has not supported Java-8 yet, can you append a non-lambda version.

akarnokd Over a year ago

Your Android Studio should be able to convert this to that format, plus you can now have lambda support: developer.android.com/studio/write/java8-support.html

CoXier Over a year ago

Thanks for your reply. But I am new to lambda, so I do need non-lambda version.

akarnokd Over a year ago

Paste in the code sample above, position on the ->, hit ALT+ENTER and pick "Replace lambda with anonymous class". Repeat for the other ->.

CoXier Over a year ago

method toList return Single<List<T>>

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