我试图创建一个数据库来存储抽认卡使用房间。我确信我已经完成了所有必要的代码,但是,当我运行我的应用程序并使用数据库检查器时,它说没有什么可显示的。我不知道为什么任何帮助将不胜感激。
实体
import androidx.room.Entity
import androidx.room.PrimaryKey
@Entity(tableName = "flashcards")
data class Flashcard(
@PrimaryKey(autoGenerate = true)
val id: Int = 0,
val question: String,
val answer: String
)
数据访问对象
import androidx.room.Dao
import androidx.room.Delete
import androidx.room.Insert
import androidx.room.OnConflictStrategy
import androidx.room.Query
import androidx.room.Update
import kotlinx.coroutines.flow.Flow
@Dao
interface FlashcardDao {
@Insert(onConflict = OnConflictStrategy.IGNORE)
suspend fun insert(flashcard: Flashcard)
@Update
suspend fun update(flashcard: Flashcard)
@Delete
suspend fun delete(flashcard: Flashcard)
@Query("SELECT * FROM flashcards WHERE id = :id")
fun getFlashcard(id: Int): Flow<Flashcard>
@Query("SELECT * FROM flashcards")
fun getAllFlashcards(): Flow<List<Flashcard>>
}
数据库类
import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase
@Database(
entities = [Flashcard::class],
version = 1,
exportSchema = false
)
abstract class FlashcardDatabase: RoomDatabase() {
abstract fun flashcardDao(): FlashcardDao
companion object {
@Volatile
private var Instance: FlashcardDatabase? = null
fun getDatabase(context: Context): FlashcardDatabase {
return Instance ?: synchronized(this) {
Room.databaseBuilder(context, FlashcardDatabase::class.java, "flashcard_database")
.fallbackToDestructiveMigration()
.build()
.also { Instance = it }
}
}
}
}
仓库接口
interface FlashCardsRepository {
fun getAllFlashcardsStream(): Flow<List<Flashcard>>
fun getFlashcardStream(id: Int): Flow<Flashcard?>
suspend fun insertFlashcard(flashcard: Flashcard)
suspend fun deleteFlashcard(flashcard: Flashcard)
suspend fun updateFlashcard(flashcard: Flashcard)
}
仓库实现类
import kotlinx.coroutines.flow.Flow
class OfflineFlashcardsRepository(private val flashcardDao: FlashcardDao) : FlashCardsRepository {
override fun getAllFlashcardsStream(): Flow<List<Flashcard>> = flashcardDao.getAllFlashcards()
override fun getFlashcardStream(id: Int): Flow<Flashcard?> = flashcardDao.getFlashcard(id)
override suspend fun insertFlashcard(flashcard: Flashcard) = flashcardDao.insert(flashcard = flashcard)
override suspend fun updateFlashcard(flashcard: Flashcard) = flashcardDao.update(flashcard = flashcard)
override suspend fun deleteFlashcard(flashcard: Flashcard) = flashcardDao.delete(flashcard = flashcard)
}
App容器(用于依赖注入)
import android.content.Context
interface AppContainer {
val flashCardsRepository: FlashCardsRepository
}
class AppDataContainer(private val context: Context): AppContainer {
override val flashCardsRepository: FlashCardsRepository by lazy {
OfflineFlashcardsRepository(FlashcardDatabase.getDatabase(context).flashcardDao())
}
}
创建数据库示例onCreate()的Flashcard应用程序(我已经将此应用程序添加到清单文件中)
import android.app.Application
import com.example.flashcardapp.data.AppContainer
import com.example.flashcardapp.data.AppDataContainer
class FlashcardApplication: Application() {
lateinit var container: AppContainer
override fun onCreate() {
super.onCreate()
container = AppDataContainer(this)
}
}
清单文件
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<application
android:name=".FlashcardApplication"
android:allowBackup="true"
android:dataExtractionRules="@xml/data_extraction_rules"
android:fullBackupContent="@xml/backup_rules"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.FlashcardApp"
tools:targetApi="31">
<activity
android:name=".MainActivity"
android:exported="true"
android:label="@string/app_name"
android:theme="@style/Theme.FlashcardApp">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
数据库检查器显示的内容
2条答案
按热度按时间w3nuxt5m1#
您的问题可能是您实际上没有访问数据库。
直到您尝试访问数据库;即插入/更新或读取数据。
简单地创建/检索房间数据库的示例不会创建数据库,实际的底层数据库的创建会延迟到需要(访问)时。因此,您需要插入/更新或读取数据,然后将创建数据库。
toe950272#
你应该概述你的代码,也放置一些断点和调试你的应用程序。看看这是初始化的情况吗?
对于其他问题,我会说你应该检查这个github repo:https://github.com/fahadammar/android_room_db
所以如果你能告诉我