Java 房间数据库-外键约束失败错误代码787

我遇到了上面的问题，即使看到其他类似的问题及其解决方案，以及关于外键的sqlite文档，我也无法解决

我知道在子表中创建外键之前，必须先在父表中存在外键。然而，即使这是第一次这样做，问题仍然存在

这就是我的程序在崩溃之前的运行方式： MainActivity->Create Trip->显示为RecyclerView->单击它输入另一个活动（传递其Trip\u id）->创建位置->选择保存时崩溃（Trip\u id、locationName、latLng）

在这种情况下，Trip有一个PK:Trip_id，而Location将其作为FK

    Process: com.example.TravelPlanner, PID: 4701
    java.lang.RuntimeException: An error occurred while executing doInBackground()
        at android.os.AsyncTask$3.done(AsyncTask.java:354)
        at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
        at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
        at java.util.concurrent.FutureTask.run(FutureTask.java:271)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: android.database.sqlite.SQLiteConstraintException: FOREIGN KEY constraint failed (code 787 SQLITE_CONSTRAINT_FOREIGNKEY[787])
        at android.database.sqlite.SQLiteConnection.nativeExecuteForLastInsertedRowId(Native Method)
        at android.database.sqlite.SQLiteConnection.executeForLastInsertedRowId(SQLiteConnection.java:995)
        at android.database.sqlite.SQLiteSession.executeForLastInsertedRowId(SQLiteSession.java:788)
        at android.database.sqlite.SQLiteStatement.executeInsert(SQLiteStatement.java:86)
        at androidx.sqlite.db.framework.FrameworkSQLiteStatement.executeInsert(FrameworkSQLiteStatement.java:51)
        at androidx.room.EntityInsertionAdapter.insert(EntityInsertionAdapter.java:64)
        at com.example.travelplanner.LocationDao_Impl.insert(LocationDao_Impl.java:110)
        at com.example.travelplanner.LocationRepository$InsertLocationAsyncTask.doInBackground(LocationRepository.java:48)
        at com.example.travelplanner.LocationRepository$InsertLocationAsyncTask.doInBackground(LocationRepository.java:39)
        at android.os.AsyncTask$2.call(AsyncTask.java:333)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)

这是在onActivityResult方法的第二个活动中创建Location对象的行

 String locationName = data.getStringExtra("locationName");
            String latLng = data.getStringExtra("latLng");

            Intent intent = getIntent();
            Bundle bundle = intent.getExtras();
            int tripId = (int)bundle.get("tripId"); // D/TRIPID: Trip id is 1

            Log.d("TRIPID", "Trip id is " + tripId);

            String[] latlong = latLng.split(",");
            double latitude = Double.parseDouble(latlong[0]);
            double longitude = Double.parseDouble(latlong[1]);
            LatLng locationLatLng = new LatLng(latitude,longitude);

 Location location = new Location(tripId, locationName, locationLatLng); 
 Log.d("LOCATIONID", "Trip id is " + location.getTripId()); // D/LOCATIONID: Trip id is 1

locationViewModel.insert(location); //crashes here

Location.class

@Entity(tableName = "location_table",foreignKeys = @ForeignKey(entity = Trip.class, parentColumns = "location_Id", childColumns = "trip_Id"),
        indices = {@Index(value = {"trip_Id"})})

public class Location {

    @PrimaryKey(autoGenerate = true)
    private int locationId;

    @ColumnInfo (name = "trip_Id")
    private int tripId;

    private String locationName;

    @TypeConverters(LatLngConverter.class)
    private LatLng latLng;


    public Location(int tripId, String locationName, LatLng latLng) {
        this.tripId = tripId;
        this.locationName = locationName;
        this.latLng = latLng;
    } 

旅行班

@Entity(tableName = "trip_table",
        indices = {@Index(value = {"location_Id"},
                unique = true)})

public class Trip {

    @PrimaryKey(autoGenerate = true) 
    @ColumnInfo (name = "location_Id")
    private int id;

    private String title;

    private String description;

    private int priority;

    //id will be auto generated so it need not be inside constructor
    public Trip(String title, String description, int priority) {
        this.title = title;
        this.description = description;
        this.priority = priority;
    } 

---

我看不出这是如何在将外键添加到父表中之前添加外键的…

显示的代码似乎没有任何问题，即使用您的代码（为了方便起见，稍微修改了一下（只需在主线程上运行long for latLng）

然后使用：-

    appDatabase = Room.databaseBuilder(this,AppDatabase.class,"travel_planner")
            .allowMainThreadQueries()
            .build();
    Trip trip1 = new Trip("A Trip","My first trip",1);
    int tripID = (int) appDatabase.tripDao().insertTrip(trip1);
    appDatabase.locationDao().insertLocation(new Location(tripID,"Here",100));
    appDatabase.locationDao().insertLocation(new Location(tripID,"Here again",200));
    List<Trip> tripList = appDatabase.tripDao().getAllTrips();
    for (Trip t: tripList) {
        Log.d("TRIPINFO","Trip is " + t.getDescription() + " ID is " + t.getId());
    }
    List<Location> locationList = appDatabase.locationDao().getAllLocations();
    for (Location l: locationList) {
        Log.d("LOCINFO","Location is " + l.getLocationName() + " ID is " + l.getLocationId() + " REFERENCES Trip " + l.getTripId());
    }

i、 e TripId1存在，并添加了两个位置，参考该行程

同样地

//在日志中显示为1不正确或

尝试添加位置时，行程不存在

出于调试目的，我建议添加以下内容：-

将以下内容添加到适当的Dao中（以下内容使用TripDao，并且

抽象TripDao TripDao（）；

在@Database类中编码（

AppDatabase

在下面使用））

:-

---

这将列出当前跳闸和要添加的位置。假设出现故障，则跳闸id和参考跳闸值之间存在差异。如果跳闸不存在，则由于某种原因，不会添加跳闸，否则将传递不正确的TripId。以上内容应有助于确定是哪种情况

感谢您再次关注我的问题。我尝试了您的方法，但我使用的是LiveData，因此我无法使用foreach获取tripId。但是，我尝试了使用Log.d（“tripId”，“Trip id为”+tripId）；在onActivityResult类中创建tripId变量后，得到了1。之后，我使用了Log.d（“LOCATIONID”，“Trip id为”+location.getTripId（））；将tripId添加到location对象后，它也显示为1。D/tripId:Trip id为1 D/LOCATIONID:Trip id为1也要注意，在start@Ferain尽管您不相信，但这表明id为1的跳闸行不存在。这就是为什么检查跳闸行是否为ta很重要的原因ble确实有这样一行。据猜测，您的问题很可能是如何从recycler视图中获取trip id。您已经尝试了您建议的方法，即使在插入新的trip数据后立即检查，for循环也不会输出任何内容。但是，我使用了SQL ite的DB Browser，它显示数据在数据库中。因此我现在真的很困惑

2019-10-31 06:28:09.591 27335-27335/? D/TRIPINFO: Trip is My first trip ID is 1 
2019- 10-31 06:28:09.593 27335-27335/? D/LOCINFO: Location is Here ID is 1 REFERENCES Trip 1 
2019-10-31 06:28:09.593 27335-27335/? D/LOCINFO: Location is Here again ID is 2 REFERENCES Trip 1

@Query("SELECT * FROM trip_table")
List<Trip> getAllTrips();

List<Trip> tripList = appDatabase.tripDao().getAllTrips();
for (Trip t: tripList) {
    Log.d("TRIPINFO","Trip is " + t.getDescription() + " ID is " + t.getId());
}
Log.d("LOCINFO","Location is " + location.getLocationName() + " ID is " + location.getLocationId() + " REFERENCES Trip " + location.getTripId());