我打算用两个外键在Android Room中创建一个数据库。每次我尝试在数据库中插入一个磁道,程序就会发生冲突,并说“外键costraint失败(代码787)”。也许你们中有人知道原因并能帮到我。
@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;
发布于 2018-06-07 05:58:53
表Kategorie
和Playlist
中的行的foreign key必须与要插入的Track
相同。
https://stackoverflow.com/questions/50729537
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