Question

我想使用 Android JetPack 中的分页库进行页面分页。我尝试了不同的方法，但是没有任何空白列表（空的 RecyclerView ）。.

我正在使用 Dagger2 ， OkHttp ， Retrofit2 。这是我的 PageKeyedPhotoDataSource ：

 override fun loadInitial(params: LoadInitialParams<Int>, callback: LoadInitialCallback<Int, Photo>) {
    networkState.postValue(NetworkState.LOADING)
    initialLoad.postValue(NetworkState.LOADING)

    // triggered by a refresh, we better execute sync
    try {
        val response = fetchPhotos(1).execute()
        if (response.isSuccessful) {
            val data = response.body()?.photos
            val items = data?.map { it } ?: emptyList()
            networkState.postValue(NetworkState.LOADED)
            initialLoad.postValue(NetworkState.LOADED)
            callback.onResult(items, null, 2)
        } else {
            initNetworkError("error code: ${response.code()}")
        }
    } catch (ioException: IOException) {
        initNetworkError(ioException.message ?: "unknown error")
    }
}

override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, Photo>) {
    networkState.postValue(NetworkState.LOADING)

    fetchPhotos(params.key).enqueue(
        object : retrofit2.Callback<PhotoService.PhotoWrapper> {
            override fun onFailure(call: Call<PhotoService.PhotoWrapper>, t: Throwable) {
                networkState.postValue(NetworkState.error(t.message ?: "unknown err"))
            }

            override fun onResponse(
                call: Call<PhotoService.PhotoWrapper>,
                response: Response<PhotoService.PhotoWrapper>
            ) {
                if (response.isSuccessful) {
                    val data = response.body()?.photos
                    val items = data?.map { it } ?: emptyList()
                    callback.onResult(items, params.key + 1)
                    networkState.postValue(NetworkState.LOADED)
                } else {
                    networkState.postValue(
                        NetworkState.error("error code: ${response.code()}"))
                }
            }
        }
    )
}

PhotoDataSourceFactory：

 val sourceLiveData = MutableLiveData<PageKeyedPhotoDataSource>()

override fun create(): DataSource<Int, Photo> {
    val source = PageKeyedPhotoDataSource(dataSource = dataSource,
        query = query)
    sourceLiveData.postValue(source)
    return source
}

这是照片库：

fun getMovies(query: String, pageSize: Int): Listing<Photo>

ViewModel：

val movies = switchMap(repoResult) { it.pagedList }!!

这是片段：

 viewModel.movies.observe(this, Observer<PagedList<Photo>>{
        adapter.submitList(it)
    })

RemoteDataSource：

fun fetchPhotos(page: Int): Call<PhotoService.PhotoWrapper> {
   return photoService.getPhotos(page)
}

这是我的 PhotoService ：

  @GET("photos")
fun getPhotos(@Query("page") page: Int = 1, @Query("per_page") per_page: Int = 15): Call<PhotoWrapper>

class PhotoWrapper(
    val photos: List<Photo>
)

希望您能理解我的问题。我只想知道为什么 RecyclerView 为空。问题是我没有错误，也不知道该怎么办。

使用使用Dagger2和Retrofit2的分页库清空RecyclerView

0 个答案: