尝试使用 Retrofit 发出获取请求时无法为 class java.lang.Object 创建调用适配器

Question

我在尝试向 NewsApi.org api 发出获取请求时遇到以下错误。根据他们的文档，一切似乎都是正确的，我的设置与我在 github.

上找到的许多教程和一些示例基本相同

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.newsfeed, PID: 12360
    java.lang.IllegalArgumentException: Unable to create call adapter for class java.lang.Object
        for method NewsApi.getBreakingNews
        at retrofit2.ServiceMethod$Builder.methodError(ServiceMethod.java:720)
        at retrofit2.ServiceMethod$Builder.createCallAdapter(ServiceMethod.java:234)
        at retrofit2.ServiceMethod$Builder.build(ServiceMethod.java:160)
        at retrofit2.Retrofit.loadServiceMethod(Retrofit.java:166)
        at retrofit2.Retrofit.invoke(Retrofit.java:145)
        at java.lang.reflect.Proxy.invoke(Proxy.java:393)
        at $Proxy1.getBreakingNews(Unknown Source)
        at com.example.newsfeed.data.API.NewsApi$DefaultImpls.getBreakingNews$default(NewsApi.kt:11)
        at com.example.newsfeed.util.NewsPagingSource.load(NewsPagingSource.kt:25)
        at androidx.paging.PageFetcherSnapshot.doInitialLoad(PageFetcherSnapshot.kt:275)
        at androidx.paging.PageFetcherSnapshot$pageEventFlow.invokeSuspend(PageFetcherSnapshot.kt:160)
        at androidx.paging.PageFetcherSnapshot$pageEventFlow.invoke(PageFetcherSnapshot.kt)
        at androidx.paging.CancelableChannelFlowKt$cancelableChannelFlow.invokeSuspend(CancelableChannelFlow.kt:30)
        at androidx.paging.CancelableChannelFlowKt$cancelableChannelFlow.invoke(CancelableChannelFlow.kt)
        at androidx.paging.SimpleChannelFlowKt$simpleChannelFlow$producer.invokeSuspend(SimpleChannelFlow.kt:57)
        at androidx.paging.SimpleChannelFlowKt$simpleChannelFlow$producer.invoke(SimpleChannelFlow.kt)
        at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:91)
        at kotlinx.coroutines.CoroutineScopeKt.coroutineScope(CoroutineScope.kt:194)
        at androidx.paging.SimpleChannelFlowKt$simpleChannelFlow$producer.invokeSuspend(SimpleChannelFlow.kt:52)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
        at kotlinx.coroutines.EventLoop.processUnconfinedEvent(EventLoop.common.kt:69)
        at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:357)
        at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
        at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:27)
        at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110)
        at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
        at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49)
        at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source)
        at androidx.lifecycle.BlockRunner.maybeRun(CoroutineLiveData.kt:174)
        at androidx.lifecycle.CoroutineLiveData.onActive(CoroutineLiveData.kt:240)
        at androidx.lifecycle.LiveData.changeActiveCounter(LiveData.java:390)
        at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:466)
        at androidx.lifecycle.LiveData$LifecycleBoundObserver.onStateChanged(LiveData.java:425)
        at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:354)
        at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:265)
        at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:307)
        at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:148)
        at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:134)
        at androidx.fragment.app.FragmentViewLifecycleOwner.handleLifecycleEvent(FragmentViewLifecycleOwner.java:88)
        at androidx.fragment.app.Fragment.performStart(Fragment.java:3028)
        at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:589)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:300)
        at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:112)
        at androidx.fragment.app.FragmentManager.moveToS

问题似乎出在我的 api 界面上，但我会分享更多代码以防有用。目前我的api界面如下：

package com.example.newsfeed.data.API

import com.example.newsfeed.data.API.ApiKey.Companion.API_KEY
import com.example.newsfeed.data.models.NewsApiResponse
import retrofit2.http.GET
import retrofit2.http.Query

interface NewsApi {

    @GET("/v2/top-headlines")
    suspend fun getBreakingNews(
        @Query("country")
        country: String = "us",
        @Query("page")
        pageNum: Int = 1,
        @Query("apiKey")
        apiKey: String = API_KEY,
        @Query("pageSize")
        pageSize: Int
    ): NewsApiResponse

}

用于 hilt 注入的网络模块：

package com.example.newsfeed.di

import com.example.newsfeed.data.API.NewsApi
import com.example.newsfeed.util.Constants.Companion.BASE_URL
import dagger.Module
import dagger.Provides
import dagger.hilt.InstallIn
import dagger.hilt.components.SingletonComponent
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import javax.inject.Singleton

@Module
@InstallIn(SingletonComponent::class)
object NetworkModule {

    @Singleton
    @Provides
    fun provideRetrofit(): Retrofit =
        Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build()


    @Provides
    @Singleton
    fun provideNewsApi(retrofit: Retrofit): NewsApi =
        retrofit.create(NewsApi::class.java)
}

我的 PagingSource 设置：

package com.example.newsfeed.util

import androidx.paging.PagingSource
import androidx.paging.PagingState
import com.bumptech.glide.load.HttpException
import com.example.newsfeed.data.API.NewsApi
import com.example.newsfeed.data.models.Article
import com.example.newsfeed.util.Constants.Companion.NEWSAPI_STARTING_PAGE_INDEX
import java.io.IOException


class NewsPagingSource(
    private val newsapi: NewsApi
): PagingSource<Int, Article>() {

    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Article> {
        val position = params.key ?: NEWSAPI_STARTING_PAGE_INDEX

        return try {

            val response = newsapi.getBreakingNews(pageNum = position, pageSize = params.loadSize)
            val articles = response.articles

            LoadResult.Page(
                data = articles,
                prevKey = if (position == NEWSAPI_STARTING_PAGE_INDEX) null else position - 1,
                nextKey = if (articles.isEmpty()) null else position + 1
            )
        } catch (exception: IOException) {
            LoadResult.Error(exception)
        } catch (exception: HttpException) {
            LoadResult.Error(exception)
        }
    }

    override fun getRefreshKey(state: PagingState<Int, Article>): Int? {
        return state.anchorPosition?.let { anchorPosition ->
            state.closestPageToPosition(anchorPosition)?.prevKey?.plus(1)
                ?: state.closestPageToPosition(anchorPosition)?.nextKey?.minus(1)
        }
    }

}

我的存储库：

package com.example.newsfeed.repository

import androidx.lifecycle.asLiveData
import androidx.paging.Pager
import androidx.paging.PagingConfig
import com.example.newsfeed.data.API.NewsApi
import com.example.newsfeed.util.NewsPagingSource
import javax.inject.Inject
import javax.inject.Singleton

@Singleton
class NewsRepository @Inject constructor(
    private val newsApi: NewsApi
) {
    fun getBreakingNews() =
        Pager(
            config = PagingConfig(
                pageSize = 20,
                maxSize = 100,
                enablePlaceholders = false
            ),
            pagingSourceFactory = { NewsPagingSource(newsApi) }
        ).flow.asLiveData()
}

视图模型：

package com.example.newsfeed.viewmodels


import androidx.lifecycle.ViewModel
import com.example.newsfeed.repository.NewsRepository
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.CoroutineScope
import javax.inject.Inject

@HiltViewModel
class NewsScreenViewModel @Inject constructor(
    val newsRepository: NewsRepository,
    private val ApplicationScope: CoroutineScope
): ViewModel() {

    val articles = newsRepository.getBreakingNews()

}

片段：

package com.example.newsfeed.ui

import android.os.Bundle
import android.view.View
import androidx.fragment.app.Fragment
import androidx.fragment.app.viewModels
import com.example.newsfeed.R
import com.example.newsfeed.adapters.NewsArticlesAdapter
import com.example.newsfeed.databinding.FragmentNewsScreenBinding
import com.example.newsfeed.viewmodels.NewsScreenViewModel
import dagger.hilt.android.AndroidEntryPoint

@AndroidEntryPoint
class NewsScreenFragment : Fragment(R.layout.fragment_news_screen) {

    private val viewModel: NewsScreenViewModel by viewModels()

    private var _binding: FragmentNewsScreenBinding? = null
    private val binding get() = _binding!!

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        _binding = FragmentNewsScreenBinding.bind(view)

        val adapter = NewsArticlesAdapter()

        binding.apply {
            newsRecyclerView.setHasFixedSize(true)
            newsRecyclerView.adapter = adapter
        }

        viewModel.articles.observe(viewLifecycleOwner) {
            adapter.submitData(viewLifecycleOwner.lifecycle, it)
        }
    }

    override fun onDestroyView() {
        super.onDestroyView()
        _binding = null
    }

}

Answer 1

您是运行没有协程支持的旧版 Retrofit。

要启用对 suspend 函数的支持，请将 Retrofit 升级到版本 2.6.0 或更高版本。

尝试使用 Retrofit 发出获取请求时无法为 class java.lang.Object 创建调用适配器

Unable to create call adapter for class java.lang.Object while trying to make get request using Retrofit

android

retrofit

retrofit2

dagger-hilt

android-paging-3