要从Room数据库访问数据并在Stack小部件中显示数据，您需要执行以下步骤：

1. 首先，创建一个Room数据库并设置必要的实体类和DAO（数据访问对象）。您可以参考以下示例：

// 定义实体类
@Entity(tableName = "note_table")
data class Note(
    @PrimaryKey(autoGenerate = true)
    val id: Int,
    val title: String,
    val content: String
)

// DAO（数据访问对象）
@Dao
interface NoteDao {
    @Query("SELECT * FROM note_table")
    fun getAllNotes(): List
}

// 数据库类
@Database(entities = [Note::class], version = 1)
abstract class NoteDatabase : RoomDatabase() {
    abstract fun noteDao(): NoteDao
}

2. 接下来，您需要在应用程序的主要堆栈小部件类中访问数据库并获取数据。请参考以下示例：

class MyStackWidgetService : RemoteViewsService() {

    override fun onGetViewFactory(intent: Intent): RemoteViewsFactory {
        return StackRemoteViewsFactory(applicationContext)
    }

    inner class StackRemoteViewsFactory(private val context: Context) : RemoteViewsFactory {

        private lateinit var noteList: List
        private lateinit var noteDao: NoteDao

        override fun onCreate() {
            val noteDatabase = Room.databaseBuilder(context, NoteDatabase::class.java, "note_db").build()
            noteDao = noteDatabase.noteDao()
        }

        override fun onDataSetChanged() {
            noteList = noteDao.getAllNotes()
        }

        override fun getViewAt(position: Int): RemoteViews {
            val remoteViews = RemoteViews(context.packageName, R.layout.widget_item_layout)
            val note = noteList[position]
            remoteViews.setTextViewText(R.id.widget_title_textview, note.title)
            remoteViews.setTextViewText(R.id.widget_content_textview, note.content)
            return remoteViews
        }

        override fun getCount(): Int {
            return noteList.size
        }

        override fun getViewTypeCount(): Int {
            return 1
        }

        // 其他未实现的方法省略...

    }
}

3. 最后，您需要在清单文件中声明堆栈小部件服务。请参考以下示例：

    
        ...
        
        
            
                
            
            
        

        

    

这样，您就可以通过Stack小部件显示来自Room数据库的数据了。