android - 具有复合键的android房间中的实体中不存在主键

Question

我得到的错误是:

error: theme_id, picture_id referenced in the primary key does not exists in the Entity. Available column names:theme_id, picture_id, image

我在网上看了很多，但找不到任何相关信息。这个错误似乎只在尝试使用复合键时弹出。如果我用普通的 PrimaryKey 注释其中一个字段，它就可以正常工作。我不明白这里发生了什么，令人沮丧的是我在网上找不到任何相关信息。我希望你们能帮助我。

实体

@Entity(primaryKeys = {"theme_id, picture_id"}, tableName = "picture")
public class Picture {

    @ColumnInfo(name = "theme_id")
    private int themeId;
    @ColumnInfo(name = "picture_id")
    private int pictureId;
    @ColumnInfo(name = "image", typeAffinity = ColumnInfo.BLOB)
    private byte[] image;
}

道

@Dao
public interface PictureDao {

    @Insert
    void instertPictures(Picture... pictures);

    @Update
    void updatePictures(Picture... pictures);

    @Delete
    void deletePictures(Picture... pictures);

    @Query("SELECT * FROM picture")
    List<Picture> getAllPictures();

    @Query("SELECT * FROM picture WHERE theme_id = :themeId")
    List<Picture> getThemePictures(int themeId);

    @Query("SELECT * FROM picture WHERE theme_id = :themeId AND picture_id = :pictureId")
    Picture getPicture(int themeId, int pictureId);

}

数据库

@Database(entities = {Picture.class}, version = 1, exportSchema = false)
public abstract class PictureDatabase extends RoomDatabase {

    public static final String NAME = "picture_db";

    public abstract PictureDao pictureDao();
}

Answer 1

您会收到此错误，因为您尚未创建名为 theme_id, picture_id 的列。可能您打算使用 2 个主键 theme_id 和 picture_id。然后你必须传递两个用逗号分隔的字符串，而不是一个内部有逗号的字符串。

所以改变

{"theme_id, picture_id"}

 "  only one string   "

到

{"theme_id", "picture_id"}

 " first  ", "  second  "
 " string "  "  string  "

它应该工作得很好。