Android Room FOREIGN KEY constraint failed (code 787)

Question

I'm tying to create a database in Android Room with two foreign keys. Every time I try to insert a track into the database the program chrashes and says that the "foreign key costraint failed(code 787)". Maybe someone of you knows why and can help me.

@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" and "Playlist" are also tables in the database.

@Entity
public class Playlist{


@PrimaryKey(autoGenerate = true)
private int uuid;

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

Kategorie

@Entity
public class Kategorie {



@PrimaryKey(autoGenerate = true)
private int kategorieID;


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

Answer 1

There's another reason why this error occurs which consumed a lot of my time since every possible solution available on the internet seemed futile in my case.

If you use rowId of the parent table as the parentColumn key , the Foreign key constraint CANNOT be used.

As per the 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.

Answer 2

您需要在表Kategorie和Playlist行具有与要插入的Track相同的外键。