Android上使用Room递归调用getDatabase时出错

我正在尝试使用Room运行查询。但是，当我尝试运行查询时，我得到以下错误

java.lang.IllegalStateException: getDatabase called recursively
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:357)
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:317)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:92)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:53)
        at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:476)
        at androidx.room.CoroutinesRoom$Companion.execute(CoroutinesRoom.kt:45)
        at androidx.room.CoroutinesRoom.execute(Unknown Source:2)
        at com.uwi.loanhub.models.UserDao_Impl.addNewUser(UserDao_Impl.java:132)
        at com.uwi.loanhub.models.LoanHubDatabase$UserDatabaseCallback.populateDatabase(LoanHubDatabase.kt:71)
        at com.uwi.loanhub.models.LoanHubDatabase$UserDatabaseCallback$onOpen$$inlined$let$lambda$1.invokeSuspend(LoanHubDatabase.kt:55)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:330)
        at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26)
        at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109)
        at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
        at kotlinx.coroutines.BuildersKt.launch(Unknown Source:1)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49)
        at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source:1)
        at com.uwi.loanhub.models.LoanHubDatabase$UserDatabaseCallback.onOpen(LoanHubDatabase.kt:54)
        at com.uwi.loanhub.models.LoanHubDatabase_Impl$1.onOpen(LoanHubDatabase_Impl.java:63)
        at androidx.room.RoomOpenHelper.onOpen(RoomOpenHelper.java:136)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onOpen(FrameworkSQLiteOpenHelper.java:142)
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:428)
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:317)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:92)
        at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:53)
        at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:476)
        at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:281)
        at com.uwi.loanhub.models.UserDao_Impl.getUsernamePassword(UserDao_Impl.java:207)
        at com.uwi.loanhub.models.UserRepository.getUsernamePassword(UserRepository.kt:15)
        at com.uwi.loanhub.models.UserViewModel.getUsernamePassword(UserViewModel.kt:31)
        at com.uwi.loanhub.LoginActivityNew$onCreate$2.onClick(LoginActivityNew.kt:54)
        at android.view.View.performClick(View.java:7125)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:992)
        at android.view.View.performClickInternal(View.java:7102)
        at android.view.View.access$3400(View.java:801)
        at android.view.View$PerformClick.run(View.java:27301)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7319)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)

调用此函数时会出现错误：

var userHolderList:List<User> = userViewModel.getUsernamePassword(editText_username_Login_Activity.text.toString(), functions.encryptSys(editText_password_Login_Activity.text.toString()))

---

在

RoomDatabase.Callback中，您不能使用房间，因为房间还没有准备好。您可以使用提供的
SupportSQLiteDatabase
执行所需的操作。
感谢您的回复。但是，我不完全理解您的意思，问题在于。@NicoleFoster在您的
UserDatabaseCallback
中，您试图使用
RoomDatabase
（
实例
）及其DAO（
数据库.UserDao（）
）。这是不受支持的。您的
onOpen（）
函数将被传递一个
SupportSQLiteDatabase
，您可以使用它。好的，当我这样做时，我得到：
无法访问主线程上的数据库，因为它可能会长时间锁定UI。
@nicoleforter:Your
CoroutineScope
的默认调度程序显然是
Dispatchers.main
。使用
scope.launch（Dispatchers.IO）
或其他工具来安排在后台线程上执行工作。是的，我尝试使用
（Dispatchers.IO）
，但它给出了相同的错误。有没有更简单的方法来做这类事情。问题是当我插入时，它工作得很好。但做一个简单的查询，我得到了这个问题。
@Database(entities = arrayOf(User::class), version = 1, exportSchema = false)
abstract class LoanHubDatabase : RoomDatabase() {

    abstract fun UserDao(): UserDao


    companion object {

        @Volatile
        private var INSTANCE: LoanHubDatabase? = null

        fun getDatabase(context: Context, scope: CoroutineScope): LoanHubDatabase {
            val tempInstance = INSTANCE
            if (tempInstance != null) {
                return tempInstance
            }

            synchronized(this) {
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    LoanHubDatabase::class.java,
                    "LoanHub_Database"
                ).addCallback(UserDatabaseCallback(scope)).build()
                INSTANCE = instance
                return instance
            }

        }

    }

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

        @RequiresApi(Build.VERSION_CODES.O)
        override fun onOpen(db: SupportSQLiteDatabase) {
            super.onOpen(db)
            INSTANCE?.let { database ->
                scope.launch {
                    populateDatabase(database.UserDao())
                }

            }
        }

        @RequiresApi(Build.VERSION_CODES.O)
        suspend fun populateDatabase(userDao: UserDao) {


        }


    }


}