如何正确使用协同程序实现会议室数据库？

Question

我正在开发新闻Android，我已经实现了要实现的空间数据库逻辑，我想先获取数据，然后保存到空间数据库，但是当我运行该应用程序时，我已经实现了该逻辑，它只显示白屏进度栏加载

下面是Android应用的屏幕截图

在MainViewmModel.kt类下面

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?.data
                newsRepository.refresh()
            }
        }
    }
}

在我的NewsRepository下，我正在其中获取数据并将其保存到数据库

class NewsRepository(private val sportNewsApi: SportNewsInterface, private val sportNewsDao: SportNewsDao) {

        val data = sportNewsDao.getAllData()

        suspend fun refresh() {
            withContext(Dispatchers.IO) {
                val articles = sportNewsApi.getNewsAsync().body()?.articles
                if (articles != null) {
                    sportNewsDao.addAll(articles)
                }
            }
        }
    }

NewsDao.kt下面

@Dao
interface 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)

}

SportNewsDatabase.kt以下

@Database(entities = [Article::class], version = 1, exportSchema = false)
@TypeConverters(SourceTypeConverters::class)
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
        }
    }


}

我想知道我在哪里出错，为什么应用程序显示空白屏幕