PositionalDataSource未显示列表

Question

我想从我们的后端服务器中获取20个Job项目。我需要获取的api是基于位置的。这就是为什么我使用PositionalDataSource

我使用Rxjava的streamData和LiveData将数据连接到UI。我需要每次滚动获取20个项目。因此，我使用PositionalDataSource进行检索。实际上，后端开发人员生成的Api是基于位置的。但是我在recyclerView中看不到任何值。

JobService.kt

@GET(Constants.API_JOB_LIST)
fun getJobPost(
    @Query("offset") numberOfItemPerRequest: Int
): Observable<Response<JobResponse>>

RetrofitBuilder.kt

fun retrofit(baseUrl: String): Retrofit = Retrofit.Builder()
    .client(getOkHttpClient())
    .baseUrl(baseUrl)
    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
    .addConverterFactory(GsonConverterFactory.create())
    .build()

private fun getOkHttpClient(): OkHttpClient {
    return OkHttpClient().newBuilder()
        .connectTimeout(3, TimeUnit.SECONDS)
        .readTimeout(3, TimeUnit.SECONDS)
        .writeTimeout(3, TimeUnit.SECONDS)
        .addInterceptor(headersInterceptor)
        .addInterceptor(loggingInterceptor)
        .build()
}

ApiUtils.kt

val loggingInterceptor = HttpLoggingInterceptor().apply {
    level = HttpLoggingInterceptor.Level.BODY
}

val headersInterceptor = Interceptor {
    val request = it.request()

    it.proceed(
        request.newBuilder()
            .addHeader("Accept", "application/json")
            .addHeader("Content-Type", "application/json")
            .addHeader("api_key", "sr8fyw8hcow8efhisncsef0wefw9ef0swdcsopd")
            .build()
    )
}

ApiFactory.kt

val jobListApi: JobService = RetrofitBuilder
    .retrofit(Constants.BASE_URL)
    .create(JobService::class.java)

JobResponse.kt

data class JobResponse(
    @field:SerializedName("msg") val msg: String? = null,
    @field:SerializedName("data") val data: List<Job?>? = null,
    @field:SerializedName("status") val status: Int? = null
)

JobDataSource.kt

class JobDataSource(
    private val jobService: JobService,
    private val compositeDisposable: CompositeDisposable
): PositionalDataSource<Job>() {

    companion object {
        private const val POSITION_OF_JOB_POST = 0
    }

    override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<Job>) {
        val initialJobList = jobService.getJobPost(POSITION_OF_JOB_POST)
        compositeDisposable += initialJobList
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe({
                if (it.isSuccessful) {
                    val jobList = it?.body()?.data!!
                    callback.onResult(
                        jobList,
                        computeInitialLoadPosition(params, jobList.size),
                        jobList.size
                    )
                } else {
                    // ... statusCode = it.code()
                }
            }, {
                if(it is IOException) {
                    // ... No Internet
                } else {
                    // ... Converter Exception(Json Parsing error)
                }
            })
    }

    override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<Job>) {
        val initialJobList = jobService.getJobPost(POSITION_OF_JOB_POST)
        compositeDisposable += initialJobList
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe({
                if (it.isSuccessful) {
                    callback.onResult(it?.body()?.data!!)
                } else {
                    // ... statusCode = it.code()
                }
            }, {
                if(it is IOException) {
                    // ... No Internet
                } else {
                    // ... Converter Exception(Json Parsing error)
                }
            })
    }

}

JobDataSourceFactory.kt

class JobDataSourceFactory(
    private val jobService: JobService,
    private val compositeDisposable: CompositeDisposable
): DataSource.Factory<Int, Job>() {

    override fun create() = JobDataSource(jobService, compositeDisposable)

}

JobDataProvider.kt

class JobDataProvider(
    private val jobService: JobService,
    private val compositeDisposable: CompositeDisposable
) {

    companion object {
        private const val PAGE_SIZE = 20
        private const val PREFETCH_DISTANCE = 20
    }

    fun getJobs(): Observable<PagedList<Job>> {
        val config = PagedList.Config.Builder()
            .setPageSize(PAGE_SIZE)
            .setInitialLoadSizeHint(PAGE_SIZE)
            .setPrefetchDistance(PREFETCH_DISTANCE)
            .setEnablePlaceholders(true)
            .build()

        return RxPagedListBuilder(
            JobDataSourceFactory(jobService, compositeDisposable),
            config
        ).buildObservable()
    }
}

JobBoardViewModel.kt

class JobBoardViewModel : BaseViewModel() {

    var jobList: LiveData<PagedList<Job>> = MutableLiveData()

    fun getJobList() {
        val observableList: Observable<PagedList<Job>> = JobDataProvider(
            ApiFactory.jobListApi,
            compositeDisposable
        ).getJobs()

        jobList = LiveDataReactiveStreams.fromPublisher(observableList.toFlowable(BackpressureStrategy.BUFFER))
    }

}

JobFragment.kt

viewModel.jobList.observe(viewLifecycleOwner, Observer {
        jobAdapter.submitList(it)
})