CoroutineScope(SupervisorJob()) 是否在 Main 范围内运行？

Question

我在做这个代码实验室 https://developer.android.com/codelabs/android-room-with-a-view-kotlin#13 有问题

class WordsApplication : Application() {
    // No need to cancel this scope as it'll be torn down with the process
    val applicationScope = CoroutineScope(SupervisorJob())

    // Using by lazy so the database and the repository are only created when they're needed
    // rather than when the application starts
    val database by lazy { WordRoomDatabase.getDatabase(this, applicationScope) }
    val repository by lazy { WordRepository(database.wordDao()) }
}

   private class WordDatabaseCallback(
       private val scope: CoroutineScope
   ) : RoomDatabase.Callback() {

       override fun onCreate(db: SupportSQLiteDatabase) {
           super.onCreate(db)
           INSTANCE?.let { database ->
               scope.launch {
                   var wordDao = database.wordDao()

                   // Delete all content here.
                   wordDao.deleteAll()

                   // Add sample words.
                   var word = Word("Hello")
                   wordDao.insert(word)
                   word = Word("World!")
                   wordDao.insert(word)

                   // TODO: Add your own words!
                   word = Word("TODO!")
                   wordDao.insert(word)
               }
           }
       }
   }

这是我找到的代码，如您所见，它直接调用 scope.launch(...) 我的问题是：不是所有 Room 操作都应该在非 UI 范围内运行吗？有人可以帮助我理解这一点吗？非常感谢！

Answer 1

Is CoroutineScope(SupervisorJob()) runs in Main scope?

没有。默认情况下 CoroutineScope() 使用 Dispatchers.Default，可以在 documentation:

中找到

CoroutineScope() uses Dispatchers.Default for its coroutines.

isn't all the Room operations supposed to run in non-UI scope?

我对Room不是特别熟悉，但总的来说要看操作是挂起还是阻塞。您可以运行暂停任何 dispatcher/thread 的功能。示例中的 deleteAll() 和 insert() 函数被标记为 suspend，因此您可以从 UI 和 non-UI 线程中运行它们。

CoroutineScope(SupervisorJob()) 是否在 Main 范围内运行？

Is CoroutineScope(SupervisorJob()) runs in Main scope?

android-room

kotlin-coroutines