Room - 不确定如何将 Cursor 转换为该方法的返回类型 (java.lang.Object)

Question

我正在使用 Room 创建一个项目，并且有以下代码：

对于我的实体类：

import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity("matches")
data class MatchEntity(
    @PrimaryKey(autoGenerate = true) @ColumnInfo(name = "id") val id: Int,
    @ColumnInfo(name = "name") val name: String,
    @ColumnInfo(name = "city") val city: String,
    @ColumnInfo(name = "distance") val distance: Int,
    @ColumnInfo(name = "description") val description: String,
    @ColumnInfo(name = "score") val score: Int,
    @ColumnInfo(name = "age") val age: Int,
    @ColumnInfo(name = "body_type") val bodyType: BodyType,
    @ColumnInfo(name = "height") val height: Float,
    @ColumnInfo(name = "diet") val diet: DietType,
    @ColumnInfo(name = "zodiac_sign") val zodiacSign: ZodiacSign,
    @ColumnInfo(name = "religion") val religion: Religion,
    @ColumnInfo(name = "drinking_habit") val drinkingHabit: DrinkingHabit,
    @ColumnInfo(name = "smoking_habit") val smokingHabit: SmokingHabit,
    @ColumnInfo(name = "mbti_type") val mbtiType: MbtiType,
    @ColumnInfo(name = "enneagram") val enneagram: Enneagram,
    @ColumnInfo(name = "kids_type") val kidsType: KidsType,
)

对于我的 DAO 类：

@Dao
interface MatchDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insert(matchEntity: MatchEntity): Long

    @Update
    suspend fun update(matchEntity: MatchEntity): Int

    @Delete
    suspend fun delete(matchEntity: MatchEntity)

    @Query("SELECT * FROM matches")
    suspend fun getAll(): List<MatchEntity>

    @Query("SELECT * FROM matches WHERE id = :id")
    suspend fun getById(id: Int): List<MatchEntity>
}

对于我的 RoomDatabase 类：

@Suppress("TooManyFunctions")
@Database(
    entities = [
        MatchEntity::class, MatchIceBreakerEntity::class, MatchInterestEntity::class,
        MatchScheduleEntity::class, MatchSocialEntity::class, MatchStoryEntity::class,
        UserEntity::class, UserIceBreakerEntity::class, UserInterestEntity::class,
        UserSocialEntity::class, UserStoryEntity::class
    ],
    exportSchema = false,
    version = 1
)
@TypeConverters(
    BodyTypeConverter::class,
    DietTypeConverter::class,
    DrinkingHabitConverter::class,
    EnneagramConverter::class,
    KidsTypeConverter::class,
    MbtiTraitConverter::class,
    MbtiTypeConverter::class,
    ReligionConverter::class,
    SleepingHabitConverter::class,
    SmokingHabitConverter::class,
    SocialConverter::class,
    SocialMediaFrequencyConverter::class,
    WorkoutTypeConverter::class,
    ZodiacSignConverter::class
)
abstract class WingmanDatabase : RoomDatabase() {

    abstract fun matchDao(): MatchDao
    abstract fun matchIceBreakerDao(): MatchIceBreakerDao
    abstract fun matchInterestDao(): MatchInterestDao
    abstract fun matchScheduleDao(): MatchScheduleDao
    abstract fun matchSocialDao(): MatchSocialDao
    abstract fun matchStoryDao(): MatcStoryDao
    abstract fun userDao(): UserDao
    abstract fun userIceBreakerDao(): UserIceBreakerDao
    abstract fun userInterestDao(): UserInterestDao
    abstract fun userSocialDao(): UserSocialDao
    abstract fun userStoryDao(): UserStoryDao

    companion object {
        const val DATABASE_NAME: String = "wingman_db"
    }
}

对于我的依赖项：

plugins {
    ...
    
    id 'kotlin-kapt'
}

...

android {

    ...

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

...

dependencies {

    ...

    def room_version = "2.5.1"
    implementation "androidx.room:room-runtime:$room_version"
    implementation "androidx.room:room-ktx:$room_version"
    kapt "androidx.room:room-compiler:$room_version"
}

对于我的 build.gradle 插件：

plugins {
    id 'com.android.application' version '8.0.1' apply false
    id 'com.android.library' version '8.0.1' apply false
    id 'androidx.navigation.safeargs' version '2.5.3' apply false
    id 'org.jetbrains.kotlin.android' version '1.9.0-Beta' apply false
}

我已经与 Room 合作了很多次，但不知何故，这次我收到了这个错误：

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:27: error: Not sure how to convert a Cursor to this method's return type (java.lang.Object).
    public abstract java.lang.Object getAll(@org.jetbrains.annotations.NotNull

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:28: error: Query method parameters should either be a type that can be converted into a database column or a List / Array that contains such type. You can consider adding a Type Adapter for this.
    kotlin.coroutines.Continuation<? super java.util.List<com.hikarisource.wingman.data.local.entity.MatchEntity>> $completion);

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:27: error: Unused parameter: $completion
    public abstract java.lang.Object getAll(@org.jetbrains.annotations.NotNull

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:32: error: Not sure how to convert a Cursor to this method's return type (java.lang.Object).
    public abstract java.lang.Object getById(int id, @org.jetbrains.annotations.NotNull

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:33: error: Query method parameters should either be a type that can be converted into a database column or a List / Array that contains such type. You can consider adding a Type Adapter for this.
    kotlin.coroutines.Continuation<? super java.util.List<com.hikarisource.wingman.data.local.entity.MatchEntity>> $completion);

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:32: error: Unused parameter: $completion
    public abstract java.lang.Object getById(int id, @org.jetbrains.annotations.NotNull

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:11: error: Type of the parameter must be a class annotated with @Entity or a collection/array of it.
    kotlin.coroutines.Continuation<? super java.lang.Long> $completion);

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:9: error: Not sure how to handle insert method's return type.
    public abstract java.lang.Object insert(@org.jetbrains.annotations.NotNull

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:21: error: Not sure how to handle delete method's return type. Currently the supported return types are void, int or Int.
    public abstract java.lang.Object delete(@org.jetbrains.annotations.NotNull

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:23: error: Type of the parameter must be a class annotated with @Entity or a collection/array of it.
    kotlin.coroutines.Continuation<? super kotlin.Unit> $completion);

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:17: error: Type of the parameter must be a class annotated with @Entity or a collection/array of it.
    kotlin.coroutines.Continuation<? super java.lang.Integer> $completion);

C:\Users\Leona\workspace\wingman\app\build\tmp\kapt3\stubs\debug\com\hikarisource\wingman\data\local\dao\MatchDao.java:15: error: Not sure how to handle update method's return type. Currently the supported return types are void, int or Int.
    public abstract java.lang.Object update(@org.jetbrains.annotations.NotNull

这是由 MatchDao 生成的代码：

plugins {
    ...
    
    id 'kotlin-kapt'
}

...

android {

    ...

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

...

dependencies {

    ...

    def room_version = "2.5.1"
    implementation "androidx.room:room-runtime:$room_version"
    implementation "androidx.room:room-ktx:$room_version"
    kapt "androidx.room:room-compiler:$room_version"
}

我将表的名称更改为martches而不是match因为显然它是match一个保留关键字。

另外，我尝试看看我的注释是否有错误，但我找不到它。

我还尝试从所有 DAO 中删除suspend，尽管我不再出现编译时错误，但我开始在运行时收到错误：

java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.

如果有人知道发生了什么事，我将不胜感激的帮助:)

Answer 1

解决方案是删除修饰符suspend。显然，即使返回类型不是像 LiveData 或 Flow 这样的 DataStream，Room 也放弃了它的使用。

现在我的 DAO 类如下所示：

@Dao
interface MatchDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(matchEntity: MatchEntity): Long

    @Update
    fun update(matchEntity: MatchEntity): Int

    @Delete
    fun delete(matchEntity: MatchEntity)

    @Query("SELECT * FROM matches")
    fun getAll(): List<MatchEntity>

    @Query("SELECT * FROM matches WHERE id = :id")
    fun getById(id: Int): List<MatchEntity>
}

请小心，因为您不应该在主线程上调用它，所以不要忘记将您的调度程序更改为 IO。