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android - 使用kotlin协程中的房间从服务器获取数据后如何将数据保存到数据库？

问题描述

我正在开发新闻应用程序我想在使用房间从服务器获取数据后将数据保存到数据库但我很困惑我已经按照教程但是他们的逻辑不同如何正确保存数据以便在从服务器获取数据后我可以保存数据到数据库？

在我的 SportNewsDatabase.kt 下面

@Database(entities = [Article::class], version = 1, exportSchema = false)
abstract class SportNewsDatabase : RoomDatabase() {

    abstract fun sportNewsDao(): SportNewsDao

    companion object {
        private var instance: SportNewsDatabase? = null
        fun getInstance( context: Context): SportNewsDatabase? {
            if (instance == null) {
                synchronized(SportNewsDatabase::class.java) {
                    instance = Room.databaseBuilder(context.applicationContext, SportNewsDatabase::class.java, "article_database")
                        .fallbackToDestructiveMigration()
                        .build()
                }
            }
            return instance
        }
    }


}

以下 SportNewsDao.kt

@Dao 界面 SportNewsDao {

@Query("SELECT * FROM  article")
fun getAllData(): LiveData<List<Article>>

@Insert
 suspend fun addAll(article: List<Article>)


@Update
 suspend fun updateArticle(article: Article)

@Delete
 suspend fun deleteArticle(article: Article)

}

below my repository class
interface NewsRepository {
    // Suspend is used to await the result from Deferred
    suspend fun getNewsList(): UseCaseResult<List<Article>>
     var sportNewsDao: SportNewsDao
}



fun insertArticle(article: List<Article>){
    val insertArticles 
}


@Suppress("UNCHECKED_CAST")
class NewsRepositoryImpl(private val sportsNewsApi: SportNewsInterface) : NewsRepository {
    override suspend fun getNewsList(): UseCaseResult<List<Article>> {

        return try {
            val result = sportsNewsApi.getNewsAsync().body()!!.articles

            UseCaseResult.Success(result)
        } catch (ex: Exception) {
            UseCaseResult.Error(ex)
        }
    }
}

在我使用 Kotlin 协程的 MainViewModel.kt 下面

@Suppress("UNCHECKED_CAST")
class MainViewModel(val newsRepository: NewsRepository) : ViewModel(), CoroutineScope {
    // Coroutine's background job
    val job = Job()
    // Define default thread for Coroutine as Main and add job
    override val coroutineContext: CoroutineContext = Dispatchers.Main + job

    val showLoading = MutableLiveData<Boolean>()
    val sportList = MutableLiveData<List<Article>>()
    val showError = SingleLiveEvent<String>()

    fun loadNews() {
        // Show progressBar during the operation on the MAIN (default) thread
        showLoading.value = true
        // launch the Coroutine
        launch {
            // Switching from MAIN to IO thread for API operation
            // Update our data list with the new one from API
            val result = withContext(Dispatchers.IO) {
                newsRepository?.getNewsList()
            }
            // Hide progressBar once the operation is done on the MAIN (default) thread
            showLoading.value = false
            when (result) {

                is UseCaseResult.Success<*> -> {
                    sportList.value = result.data as List<Article>
                }
                is Error -> showError.value = result.message
            }
        }
    }

    override fun onCleared() {
        super.onCleared()
        // Clear our job when the linked activity is destroyed to avoid memory leaks
        job.cancel()
    }
}

标签： androiddatabaseandroid-roomkotlin-coroutines

解决方案

@sashabeliy

嗨，我想我有你的问题的解决方案，但我不是 mvvm 和协程方面的专家，所以如果有人有更好的解决方案，我会接受 :)

对于我的应用程序，我在主线程中启动下载，并且只有当我得到响应时，我才使用 Dispatchers.IO 在 Room 中插入接收到的数据。

在视图模型中

fun downLoadPDV(last_update : String) : LiveData<List<PDV>> { return repositoryPDV.downloadPDV(last_update) }

在存储库中

fun downloadPDV(last_update : String ): LiveData<List<PDV>> {
    val mutableLiveData: MutableLiveData<List<PDV>> = MutableLiveData()
    val apiService: ApiInterface = RetrofitClient.getRetrofitClient().create(ApiInterface::class.java)

    apiService.CallListPDV(last_update)?.enqueue(object :
        Callback<List<PDV>> {
        override fun onResponse(
            call: Call<List<PDV>>,
            response: Response<List<PDV>>
        ) {
            Log.e(ContentValues.TAG, "Download PDV Success => $response")

            if (response.isSuccessful && response.body() != null) {

                mutableLiveData.setValue(response.body());

                GlobalScope.launch(Dispatchers.IO) {
                    for (pdv in response.body()!!) {
                        insertPDV(pdv)
                    }
                }
            }
        }

        override fun onFailure(call: Call<List<PDV>>, t: Throwable) {
            Log.e(ContentValues.TAG, "[Error] Download PDV Fail --> $call")
        }
    })
    return mutableLiveData
}

我返回数据下载以更新 UI，并通知用户下载了多少项目

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