Android Hilt Retrofit Paging3使用实例

 //retrofit
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
    //paging
    implementation 'Androidx.paging:paging-runtime:3.1.1'
    implementation 'androidx.paging:paging-compose:1.0.0-alpha14'
    //Dagger - Hilt
    implementation("com.Google.dagger:hilt-android:2.44")
    kapt("com.google.dagger:hilt-android-compiler:2.44")
    // Compose dependencies
    implementation "androidx.lifecycle:lifecycle-viewmodel-compose:2.5.1"
    implementation "androidx.hilt:hilt-navigation-compose:1.0.0"
    // Coroutines
    implementation 'org.jetbrains.Kotlinx:kotlinx-coroutines-core:1.5.1'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4'

interface githubService {
    @GET("search/repositories?sort=stars&q=Android")
    suspend fun queryGithubAsync(@Query("per_page")number:Int, @Query("page") page:Int):DetailsBean
}

@Module
@InstallIn(SingletonComponent::class)
object AppModule {
    const val BASE_URL:String = "https://api.github.com/"
    @Singleton
    @Provides
    fun providerRetrofit():Retrofit{
        return Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build()
    }
    @Singleton
    @Provides
    fun providerGithubService(retrofit: Retrofit): GithubService {
        return retrofit.create(GithubService::class.java)
    }
    @Singleton
    @Provides
    fun providerUseCase(service: GithubService):UseCase{
        return UseCase(GetProjects(service))
    }
}

data class UseCase(
    val getProjects: GetProjects
)

class GetProjects(private val service: GithubService) {
    suspend operator fun invoke(number:Int,page:Int): DetailsBean {
        return service.queryGithubAsync(number, page)
    }
}

class DataPagingSource(private val useCase: UseCase):PagingSource<Int,DetailBean>() {
    override fun getRefreshKey(state: PagingState<Int, DetailBean>): Int? = null
    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, DetailBean> {
       return try {
           val page = params.key ?: 1 //当前页，默认第一页
           val pageSize = params.loadSize //每页数据条数
           val repository = useCase.getProjects(page,pageSize) //获取的数据源
           val repositoryItem = repository.beans //获取的数据列表
           val previousPage = if (page > 1) page - 1 else null //前一页
           val nextPage = if (repositoryItem.isNotEmpty()) page+1 else null //下一页
           Log.d("hiltViewModel","page=$page size=$pageSize")
           LoadResult.Page(repositoryItem,previousPage,nextPage)
       }catch (e:Exception){
           LoadResult.Error(e)
       }
    }
}

@HiltViewModel
class HomeViewModel @Inject constructor(private val useCase: UseCase):ViewModel() {
    val PAGE_SIZE = 10
    fun getData():Flow<PagingData<DetailBean>>{
        return Pager(
            config = PagingConfig(pageSize = PAGE_SIZE, initialLoadSize = PAGE_SIZE),
            pagingSourceFactory = { DataPagingSource(useCase) }
        ).flow.cachedIn(viewModelScope)
    }
}

val datas = viewModel.getData().collectAsLazyPagingItems()

@Composable
fun GithubList(viewModel: HomeViewModel = hiltViewModel()){
    val datas = viewModel.getData().collectAsLazyPagingItems()
    LazyColumn(
        verticalArrangement = Arrangement.spacedBy(10.dp),
        modifier = Modifier
            .background(grey)
            .fillMaxSize()
            .padding(10.dp)
    ){
        when(datas.loadState.refresh){
            is LoadState.Loading-> {item {  loading() }}
            is LoadState.Error-> {
                if (datas.itemCount <= 0){
                    item{
                        
                        failedScreen() {
                            datas.retry()
                        }
                    }
                }
            }
        }
        itemsIndexed(datas){ _, value ->
            if (value != null){
                GithubItem(value)
            }else{
                empty {
                    datas.retry()
                }
            }
        }
        when(datas.loadState.append){
            is LoadState.NotLoading-> {}
            is LoadState.Loading-> {
                item {
                    loading()
                }
            }
            is LoadState.Error-> {
                if (datas.itemCount > 0){
                    
                    item { failed(){datas.retry()} }
                }
            }
        }
    }
}