android - Kotlin:如何继承RxJava Subscriber

Question

我希望我的 NewsListSubscriber 继承自使用通用类型的 RxJava 订阅者，但在调用 UseCase 执行方法时出现“类型不匹配”错误。我多次阅读 Kotlin 文档中的泛型页面，但找不到解决方案。

这是我的用例:

abstract class UseCase(private val threadExecutor: IThreadExecutor,
                       private val postExecutionThread: IPostExecutionThread) {

    private var subscription = Subscriptions.empty()

    fun execute(UseCaseSubscriber: rx.Subscriber<Any>) {
        subscription = buildUseCaseObservable()
                .subscribeOn(Schedulers.from(threadExecutor))
                .observeOn(postExecutionThread.getScheduler())
                .subscribe(UseCaseSubscriber)
    }

    protected abstract fun buildUseCaseObservable(): Observable<out Any>

    fun unsubscribe() {
        if (!subscription.isUnsubscribed) {
            subscription.unsubscribe()
        }
    }
}

我是这样调用它的:

override fun loadNewsList() {
    getNewsListInteractor.execute(NewsListSubscriber())
}

private inner class NewsListSubscriber : rx.Subscriber<List<NewsModel>>() {
    override fun onCompleted() {// TODO}

    override fun onError(e: Throwable) {// TODO}

    override fun onNext(t: List<NewsModel>) {// TODO}
}

错误是

"Type mismatch. Required: rx.Subscriber. Found: Presenters.NewsListPresenter.NewsListSubscriber"

在“执行(NewsListSubscriber())”行中。我尝试使用“in”和“out”关键字，但我仍然遇到同样的错误。

Answer 1

其实有更好的方法来解决这个问题。我遇到了同样的问题，并且在每个派生订阅者类中进行类型转换不是一种选择。

只需使用通用类型参数更新抽象 UseCase 类即可。

abstract class UseCase<T>(private val threadExecutor: IThreadExecutor,
                   private val postExecutionThread: IPostExecutionThread) {

    private var subscription = Subscriptions.empty()

    fun execute(UseCaseSubscriber: rx.Subscriber<T>) {
        subscription = buildUseCaseObservable()
                .subscribeOn(Schedulers.from(threadExecutor))
                .observeOn(postExecutionThread.getScheduler())
                .subscribe(UseCaseSubscriber)
    }

    protected abstract fun buildUseCaseObservable(): Observable<T>

    fun unsubscribe() {
        if (!subscription.isUnsubscribed) {
            subscription.unsubscribe()
        }
    }
}

当您声明您的派生用例类时，在调用父类(super class)时使用您的具体类型作为泛型参数。

class ConcreteUseCase(val threadExecutor: IThreadExecutor,
               val postExecutionThread: IPostExecutionThread)
               : UseCase<ConcreteType>(threadExecutor, postExecutionThread)

这样，您就可以在execute 调用中使用类型化订阅者。

getNewsListInteractor.execute(NewsListSubscriber())

...

private inner class NewsListSubscriber : rx.Subscriber<List<NewsModel() {
    override fun onCompleted() {// TODO}

    override fun onError(e: Throwable) {// TODO}

    override fun onNext(t: List<NewsModel>) {// TODO}
}