Android 工作室和房间 - 外键和约束失败

Question

我正在尝试使用Room数据库制作一个应用程序。我有一张桌子鸟和一张桌子家庭。(一对多关系)。

@Entity(tableName ="bird",
foreignKeys =
@ForeignKey(entity = Family.class,
parentColumns = "id",
childColumns = "familyId",
onDelete = CASCADE),
indices = {@Index("familyId")})

public class Bird {
@PrimaryKey(autoGenerate = true)
private int id;
private int familyId;
private String name;
private String family;
private String description;
private String biology;
public Bird(@NonNull String name, @NonNull String family, String description, String biology){
this.name = name;
this.family = family;
this.description= description;
this.biology = biology;
this.familyId = familyId;
}

@Entity(tableName = "family")
public class Family {
@PrimaryKey(autoGenerate = true)
private int id;
private String family;
public Family(@NonNull String family)
{
this.family = family;
}

每次我尝试运行我的鸟列表(在实现家庭实体之前工作正常)时，什么都没有显示，当我尝试使用@Insert查询添加新鸟时，我受到以下打击：

Caused by: android.database.sqlite.SQLiteConstraintException: FOREIGN KEY constraint failed (code 787 SQLITE_CONSTRAINT_FOREIGNKEY)
at android.database.sqlite.SQLiteConnection.nativeExecuteForLastInsertedRowId(Native Method)
at android.database.sqlite.SQLiteConnection.executeForLastInsertedRowId(SQLiteConnection.java:879)
at android.database.sqlite.SQLiteSession.executeForLastInsertedRowId(SQLiteSession.java:790)
at android.database.sqlite.SQLiteStatement.executeInsert(SQLiteStatement.java:88)
at androidx.sqlite.db.framework.FrameworkSQLiteStatement.executeInsert(FrameworkSQLiteStatement.java:51)
at androidx.room.EntityInsertionAdapter.insert(EntityInsertionAdapter.java:64)
at com.example.room.Dao_Impl.insertBird(Dao_Impl.java:115)
at com.example.room.BirdRepository$InsertBirdAsyncTask.doInBackground(BirdRepository.java:56)
at com.example.room.BirdRepository$InsertBirdAsyncTask.doInBackground(BirdRepository.java:45)
at android.os.AsyncTask$3.call(AsyncTask.java:378)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 
at java.lang.Thread.run(Thread.java:919)

你们知道这是从哪里来的吗？

我也是以这种方式填充数据库吗？

private static void fillWithSartingData(Context context){
Dao dao = getInstance(context).dao();
FamilyDao familyDao = getInstance(context).familyDao();
JSONArray birds = loadJSONArray(context);
JSONArray families = loadJSONArray(context);
try{
for(int i = 0; i< families.length(); i++){
JSONObject familyObj = families.getJSONObject(i);
String family = familyObj.getString("FamilieF");
familyDao.insertFamily(new Family(family));
}

for(int i = 0; i< birds.length(); i++){
JSONObject bird = birds.getJSONObject(i);
String engName = bird.getString("NameEng");
String family = bird.getString("FamilieF");
String description = bird.getString("Description");
String biology = bird.getString("Biologie");
dao.insertBird(new Bird(engName, family, description, biology));
}
} catch (JSONException e){
}
}

谢谢！ 亚历克斯

Answer 1

您违反了外键约束"外键约束失败(代码 787 SQLITE_CONSTRAINT_FOREIGNKEY)"，因为您没有在 Bird 类中设置familyId

在插入 Bird 之前，您必须在类Bird中设置familyId

为此，请像这样向 Bird 构造函数添加一个familyId参数：

public Bird(@NonNull String name, @NonNull String family, String description, String biology, long familyId){
this.name = name;
this.family = family;
this.description= description;
this.biology = biology;
this.familyId = familyId;
}

familyDao中的insertFamily应该返回 Long(如果它有一个 Family 参数)或 Long Array(如果它有一个 vararg Family 参数)，然后您从insertFamily获取插入的 family 的 id，并按familyId使用它，如下所示：

for(int i = 0; i< families.length(); i++){
JSONObject familyObj = families.getJSONObject(i);
String family = familyObj.getString("FamilieF");
long familyId = familyDao.insertFamily(new Family(family));// get familyId

for(int i = 0; i< birds.length(); i++){
JSONObject bird = birds.getJSONObject(i);
String engName = bird.getString("NameEng");
String family = bird.getString("FamilieF");
String description = bird.getString("Description");
String biology = bird.getString("Biologie");
dao.insertBird(new Bird(engName, family, description, biology, familyId));// use familyId
}