java - Observable<List<Object>> 无法转换为 Observable<List<Anime>>

Question

我收到错误“不兼容的类型:Observable<List<Object>> 无法转换为 Observable<List<Anime>>”

public Observable<List<Anime>> getOnlyAnimeObservable() {
    List onlyAnimeList = getOnlyAnimeList();
    if (onlyAnimeList == null) {
        return Observable.just(Collections.emptyList());  //Required <List<Class>> But Found <List<Object>>
    }
    return Observable.just(onlyAnimeList); //Required <List<Class>> But Found <List>
}

如果我改变public Observable<List<List<Anime>> getOnlyAnimeObservable()至

public Observable<List<Object>> getOnlyAnimeObservable() 

return Observable.just(Collections.emptyList()); error solved but return Observable.just(onlyAnimeList); still shows error

同时如果我改public Observable<List<List<Anime>> getOnlyAnimeObservable()至public Observable<List> getOnlyAnimeObservable()

return Observable.just(onlyAnimeList); error solved but return Observable.just(Collections.emptyList()); shows error.

Answer 1

这是因为Collections.emptyList()返回List<Object> 。试试这个代码:

List<Anime> list = Collections.emptyList();
return Observable.just(list);

getOnlyAnimeList方法还应该返回 List<Anime>类型。所以完整的代码应该是:

 public Observable<List<Anime>> getOnlyAnimeObservable() {
    List<Anime> onlyAnimeList = getOnlyAnimeList();
    if (onlyAnimeList == null) {
        List<Anime> list = Collections.emptyList();
        return Observable.just(list);
    }
    return Observable.just(onlyAnimeList);
 }

我们可以简化一切:

public Observable<List<Anime>> getOnlyAnimeObservable() {
    List<Anime> list = getOnlyAnimeList();
    if (list == null) {
        list = Collections.emptyList();
    }
    return Observable.just(list);
}