要在Android Room中插入复杂对象自引用表,可以按照以下步骤进行:
@Entity(tableName = "complex_table")
data class ComplexObject(
@PrimaryKey val id: Int,
val name: String,
val parentId: Int?
)
@Dao
interface ComplexObjectDao {
@Insert
suspend fun insert(complexObject: ComplexObject)
@Query("SELECT * FROM complex_table WHERE parentId = :parentId")
suspend fun getChildObjects(parentId: Int): List
}
@Database(entities = [ComplexObject::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
abstract fun complexObjectDao(): ComplexObjectDao
companion object {
@Volatile
private var instance: AppDatabase? = null
fun getInstance(context: Context): AppDatabase {
return instance ?: synchronized(this) {
instance ?: buildDatabase(context).also { instance = it }
}
}
private fun buildDatabase(context: Context): AppDatabase {
return Room.databaseBuilder(context, AppDatabase::class.java, "my-database")
.build()
}
}
}
val complexObjectDao = AppDatabase.getInstance(context).complexObjectDao()
// 插入数据
val parentObject = ComplexObject(1, "Parent", null)
val childObject = ComplexObject(2, "Child", parentObject.id)
runBlocking {
complexObjectDao.insert(parentObject)
complexObjectDao.insert(childObject)
}
// 查询数据
runBlocking {
val childObjects = complexObjectDao.getChildObjects(parentObject.id)
childObjects.forEach {
Log.d("TAG", "Child Object - id: ${it.id}, name: ${it.name}, parentId: ${it.parentId}")
}
}
通过以上步骤,我们可以在Android Room中成功插入复杂对象自引用表,并进行查询操作。