错误：实体类必须用@Entity注解答案

【问题标题】：error: Entity class must be annotated with @Entity错误：实体类必须用@Entity注解
【发布时间】：2018-07-12 03:23:48
【问题描述】：

我决定将 kotlin 与 Room 库一起使用，但我确实遇到了很多问题，并且厌倦了阅读参考资料和寻找解决方案我的数据类：

@Entity
data class HistorySong(
        @PrimaryKey
        var SongId: Int =0,

        @ColumnInfo(name = "song_name")
        var songName: String="",

        @ColumnInfo(name = "song_artist")
        var songArtist: String="",

        @ColumnInfo(name = "song_link")
        var songLink: String="",

        @ColumnInfo(name = "image_path")
        var songImagePath: String="",

        @ColumnInfo(name="is_favoutire")
        var songisFavourite: Boolean= false
)

我的道课：

@Dao
 interface HistorySongDao {

       @Delete
       fun deleteSong(historySongDao: HistorySongDao)

       @Insert(onConflict = OnConflictStrategy.REPLACE)
        fun insert(vararg historySongDao: HistorySongDao)

       @Query("SELECT * FROM HistorySong")
        fun loadAllSongs(): Array<HistorySong>


       @Query("SELECT * FROM HistorySong WHERE songId = :mId")
        fun findById(mId: Int): HistorySong

       @Query("SELECT * FROM HistorySong WHERE is_favoutire = :getFavourite ")
        fun getFavourite(getFavourite : Boolean) : Array<HistorySong>



       @Update
       fun updateUsers(vararg historySong: HistorySong)
}

数据库类：

@Database(entities = arrayOf(QueuedSong::class, HistorySongDao::class), version = 2)
abstract class AppDataBase : RoomDatabase() {
    abstract fun queuedSongDao(): QueuedSongDao
    abstract fun historySongDao(): HistorySongDao
}

QueuedSong 运行良好，但 historySong 中的问题是：

e: F:\SmartStreamer\app\build\tmp\kapt3\stubs\debug\com\pro\smartstreamer\Database\QueuedDatabase\HistorySongDao.java:7: error: Entity class must be annotated with @Entity
public abstract interface HistorySongDao {
                ^
w: F:\SmartStreamer\app\build\tmp\kapt3\stubs\debug\com\pro\smartstreamer\Database\QueuedDatabase\AppDataBase.java:10: warning: Room cannot create an SQLite connection to verify the queries. Query verification will be disabled. Error: [SQLITE_ERROR] SQL error or missing database (near ")": syntax error)
public abstract class AppDataBase extends android.arch.persistence.room.RoomDatabase {
                ^
w: F:\SmartStreamer\app\build\tmp\kapt3\stubs\debug\com\pro\smartstreamer\Database\QueuedDatabase\HistorySong.java:10: warning: There are multiple good constructors and Room will pick the no-arg constructor. You can use the @Ignore annotation to eliminate unwanted constructors.
public final class HistorySong {
             ^
e: F:\SmartStreamer\app\build\tmp\kapt3\stubs\debug\com\pro\smartstreamer\Database\QueuedDatabase\HistorySongDao.java:15: error: Type of the parameter must be a class annotated with @Entity or a collection/array of it.
    com.pro.smartstreamer.Database.QueuedDatabase.HistorySongDao... historySongDao);
                                                                    ^
e: F:\SmartStreamer\app\build\tmp\kapt3\stubs\debug\com\pro\smartstreamer\Database\QueuedDatabase\HistorySongDao.java:11: error: Type of the parameter must be a class annotated with @Entity or a collection/array of it.
    com.pro.smartstreamer.Database.QueuedDatabase.HistorySongDao historySongDao);
                                                                 ^
e: F:\SmartStreamer\app\build\tmp\kapt3\stubs\debug\com\pro\smartstreamer\Database\QueuedDatabase\HistorySongDao.java:30: error: com.pro.smartstreamer.Database.QueuedDatabase.HistorySongDao is part of com.pro.smartstreamer.Database.QueuedDatabase.AppDataBase but this entity is not in the database. Maybe you forgot to add com.pro.smartstreamer.Database.QueuedDatabase.HistorySong to the entities section of the @Database?
    public abstract void updateUsers(@org.jetbrains.annotations.NotNull()

和：

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:kaptDebugKotlin'.
> Compilation error. See log for more details

我真的找不到解决办法.. 提前致谢

【问题讨论】：

对于初学者，您尝试插入和删除 HistorySongDao 对象而不是 HistorySong 对象。看看修复是否有助于解决其中一些错误。

标签： android kotlin android-room

【解决方案1】：

我通过更改 @Database 的参数（RoomDatabase 类）解决了这个问题，但我没有意识到并将我的 DAO 放在应该是我的实体的位置。

就我而言：

@Database(entities = [WordDao::class],version = 1)

改为：

@Database(entities = [WordEntity::class],version = 1)

所以，当有人收到这个错误时，也许不仅要检查实体的声明位置，还要检查它的使用位置。

【讨论】：

成功了。我真的很新来使用房间。浪费了很多时间。
@felipe 你是个传奇，谢谢你为我指明了正确的方向！！

【解决方案2】：

正如第一条评论中所说，您尝试插入和删除 HistorySongDao 对象而不是 HistorySong，您的代码将变为：

@Dao
 interface HistorySongDao {

       @Delete
       fun deleteSong(vararg historySong: HistorySong)

       @Insert(onConflict = OnConflictStrategy.REPLACE)
        fun insert(vararg historySong: HistorySong)

       @Query("SELECT * FROM HistorySong")
        fun loadAllSongs(): Array<HistorySong>

       @Query("SELECT * FROM HistorySong WHERE songId = :mId")
        fun findById(mId: Int): HistorySong

       @Query("SELECT * FROM HistorySong WHERE is_favoutire = :getFavourite ")
        fun getFavourite(getFavourite : Boolean) : Array<HistorySong>

       @Update
       fun updateUsers(vararg historySong: HistorySong)
}

【讨论】：

【解决方案3】：

将数据库类更新为此

@Database(entities = arrayOf(QueuedSong::class, HistorySong::class), version = 2)
abstract class AppDataBase : RoomDatabase() {
abstract fun queuedSongDao(): QueuedSongDao
abstract fun historySongDao(): HistorySongDao
}

我将 HistorySongDao.class 更改为 HistorySong.class

【讨论】：

【解决方案4】：

你在你的数据库类中误用了实体。也许你调用的是 Dao Interface 而不是 Entity 类。

【讨论】：

你能说出答案中的类名吗？对理解会更有帮助。
在此处打开您的数据库类.. @Database (entities ={Entity.class}, version=1,exportedSchema =false) > 看看这里的实体={ } 部分，也许您正在调用你的 Dao 界面或其他东西。

【解决方案5】：

对我来说这是一个不同的问题：[ 而不是 {

我说：

@Database(entities = [Sensor.class, Meter.class],version = 2)

代替：

@Database(entities ={Sensor.class, Meter.class}, version = 2)

【讨论】：