Question

我正在尝试使用Fountain（https://github.com/xmartlabs/fountain）来帮助我处理分页和本地/远程数据源。

我正在这样调用库的内部函数：

FountainRx.createNetworkWithCacheSupportListing(
networkDataSourceAdapter = networkDataSourceAdapter,
cachedDataSourceAdapter = cachedDataSourceAdapter,
firstPage = FountainConstants.DEFAULT_FIRST_PAGE,
ioServiceScheduler = Schedulers.io(),
ioDatabaseScheduler = Schedulers.io(),
pagedListConfig = FountainConstants.DEFAULT_PAGED_LIST_CONFIG)

但是我得到的只是这个编译器错误：

Type inference failed: Cannot infer type parameter NetworkValue in fun <NetworkValue, DataSourceValue> createNetworkWithCacheSupportListing(networkDataSourceAdapter: RxNetworkDataSourceAdapter<out ListResponse<out NetworkValue>>, cachedDataSourceAdapter: CachedDataSourceAdapter<NetworkValue, DataSourceValue>, ioServiceScheduler: Scheduler = ..., ioDatabaseScheduler: Scheduler = ..., firstPage: Int = ..., pagedListConfig: PagedList.Config = ...): Listing<DataSourceValue>

None of the following substitutions 
(RxNetworkDataSourceAdapter<out ListResponse<out BeerListResponse<List<Beer>>>>,CachedDataSourceAdapter<BeerListResponse<List<Beer>> Any?>,Scheduler,Scheduler,Int,PagedList.Config)
(RxNetworkDataSourceAdapter<out ListResponse<out List<Beer>>>,CachedDataSourceAdapter<List<Beer>, Any?>,Scheduler,Scheduler,Int,PagedList.Config) 

can be applied to
(RxNetworkDataSourceAdapter<BeerListResponse<List<Beer>>>,CachedDataSourceAdapter<BeerListResponse<List<Beer>>, Beer>,Int,Scheduler,Scheduler,PagedList.Config))

有什么问题的想法吗？

下面您可以找到创建RxNetworkDataSourceAdapter的代码：

private fun createNetworkDataSourceAdapter(): RxNetworkDataSourceAdapter<BeerListResponse<List<Beer>>> {
        val pageFetcher = object : RxPageFetcher<BeerListResponse<List<Beer>>> {
            override fun fetchPage(page: Int, pageSize: Int): Single<BeerListResponse<List<Beer>>> =
                remoteSource.getBeers(page = page, pageSize = pageSize)
        }
        return pageFetcher.toTotalEntityCountNetworkDataSourceAdapter()
    }

如果您需要更多信息，请告诉我！在此先感谢：）

Answer 1

我解决了！就像编译器说的那样，是类型推断问题。

使用以下代码：

override fun getAllBeers(): Listing<Beer> {
        val networkDataSourceAdapter: RxNetworkDataSourceAdapter<out BeerListResponse<out List<Beer>>> = createNetworkDataSourceAdapter()
        val cachedDataSourceAdapter: CachedDataSourceAdapter<List<Beer>,Beer> = getBeerLocalSource()
        return FountainRx.createNetworkWithCacheSupportListing(
            networkDataSourceAdapter = networkDataSourceAdapter,
            cachedDataSourceAdapter = cachedDataSourceAdapter,
            firstPage = FountainConstants.DEFAULT_FIRST_PAGE,
            ioServiceScheduler = Schedulers.io(),
            ioDatabaseScheduler = Schedulers.io(),
            pagedListConfig = FountainConstants.DEFAULT_PAGED_LIST_CONFIG)
    }

使用out kotlin关键字来显式类型，错误消息终于消失了。

此Kotlin文档页面中的更多信息：https://kotlinlang.org/docs/reference/generics.html

Android Fountain Library-类型推断失败：无法在有趣的createNetworkWithCacheSupportListing中推断类型参数NetworkValue

1 个答案: