Android 房间 FOREIGN KEY 约束失败（代码 787）

Question

我想在 Android 房间里用两个外键创建一个数据库。每次我尝试将曲目插入数据库时，程序都会崩溃并显示 "foreign key costraint failed(code 787)"。也许你们中有人知道为什么并且可以帮助我。

@Entity(foreignKeys = {@ForeignKey(
    entity = Kategorie.class,
    childColumns = "kategorieFremdschluessel",
    parentColumns = "kategorieID",
    onUpdate = ForeignKey.CASCADE,
    onDelete = ForeignKey.CASCADE
    ),
    @ForeignKey(
            entity = Playlist.class,
            childColumns = "playlistFremdschluessel",
            parentColumns = "uuid",
            onUpdate = ForeignKey.CASCADE,
            onDelete = ForeignKey.CASCADE
    )
 })

public class Track {

@PrimaryKey(autoGenerate = true)
private int uid;

private String trackTitel;
private String playlistName;
private String jsonObjectString;
private int kategorieFremdschluessel;
private int playlistFremdschluessel;

@Ignore
public Track(String trackTitel, String playlistName, String jsonObjectString) {
    this.trackTitel = trackTitel;
    this.playlistName = playlistName;
    this.jsonObjectString = jsonObjectString;
}

public Track(String trackTitel, String jsonObjectString) {
    this.trackTitel = trackTitel;
    this.jsonObjectString = jsonObjectString;
}
//Getter and Setter

@Dao

TrackDao

public interface TrackDao {

@Query("SELECT * FROM Track WHERE playlistName LIKE :playlist")
List<Track> getAllTracks(String playlist);

@Query("SELECT * FROM Track WHERE kategorieFremdschluessel = :kategorieFremdschluessel")
List<Track> loadAllKategorieTracks(int kategorieFremdschluessel);

@Query("SELECT * FROM Track WHERE playlistFremdschluessel = :playlistFremdschluessel")
List<Track> loadAllPlaylistTracks(int playlistFremdschluessel);

@Insert
void insertAll(List<Track> trackList);

@Insert
void insertOne(Track track);

@Update
void updateOne(Track track);

@Delete
void delete(Track track);
}

"Kategorie" 和 "Playlist" 也是数据库中的表。

@Entity
public class Playlist{


@PrimaryKey(autoGenerate = true)
private int uuid;

@ColumnInfo(name = "name")
private String name;

类别

@Entity
public class Kategorie {



@PrimaryKey(autoGenerate = true)
private int kategorieID;


@ColumnInfo(name = "name")
private String name;

Answer 1

您需要在表 Kategorie 和 Playlist 中使用与要插入的 Track 相同的 foreign key 行。

Answer 2

发生此错误还有另一个原因，它占用了我很多时间，因为互联网上可用的所有可能解决方案对我来说似乎都是徒劳的。

如果使用父table的rowId作为parentColumn键，外键不能使用约束。

根据 SQLite documentation on Foreign Keys:

The parent key is the column or set of columns in the parent table that the foreign key constraint refers to. This is normally, but not always, the primary key of the parent table. The parent key must be a named column or columns in the parent table, not the rowid.

Android 房间 FOREIGN KEY 约束失败（代码 787）

Android Room FOREIGN KEY constraint failed (code 787)

android

sql

orm

android-room

android-orm