我遇到了上述问题，即使在查看其他类似问题及其解决方案以及外键上的sqlite文档时也无法解决。
我知道外键必须先存在于父表中，然后才能在子表中创建。但是，即使先完成了，问题仍然存在。
这是我的程序流向崩溃点的方式： MainActivity->创建行程->显示为RecyclerView->单击以输入另一个活动（通过其trip_id）->创建位置->选择保存（trip_id，locationName，latLng）时崩溃
在这种情况下，Trip拥有一个PK：trip_id，而Location则将其视为FK。
public class NoteAdapter extends RecyclerView.Adapter<NoteAdapter.ViewHolder> {
public static final int UNCOMPLETED = 0;
public static final int COMPLETED = 1;
public static final int HIGHTLIGHT = 2;
public static final int HIGHTLIGHT_COMPETED = 3;
Cursor cursor;
Context context;
public NoteAdapter(Context context, Cursor cursor) {
this.context = context;
this.cursor = cursor;
}
public Cursor getCursor() {
return this.cursor;
}
public void setCursor(Cursor cursor) {
this.cursor = cursor;
}
public Context getContext() {
return context;
}
public void setContext(Context context) {
this.context = context;
}
@Override
public int getItemViewType(int position) {
if (cursor.moveToPosition(position)) {
cursor.move(position);
String content = cursor.getString(cursor.getColumnIndex(DatabaseHandler.KEY_CONTENT));
int completed = cursor.getInt(cursor.getColumnIndex(DatabaseHandler.KEY_COMPLETED));
int hightlight = cursor.getInt(cursor.getColumnIndex(DatabaseHandler.KEY_HIGHTLIGHT));
if (completed == 1) {
if (hightlight == 1) {
return HIGHTLIGHT_COMPETED;
}
return COMPLETED;
}
if (hightlight == 1 && completed == 0) {
return HIGHTLIGHT;
}
return UNCOMPLETED;
}
return -1;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(context);
View view = inflater.inflate(R.layout.item_row, parent, false);
switch (viewType) {
case UNCOMPLETED:
view = inflater.inflate(R.layout.item_row, parent, false);
break;
case COMPLETED:
view = inflater.inflate(R.layout.item_row_completed, parent, false);
break;
case HIGHTLIGHT:
view = inflater.inflate(R.layout.item_row_hightlight, parent, false);
break;
case HIGHTLIGHT_COMPETED:
view = inflater.inflate(R.layout.item_row_hightlight_completed, parent, false);
break;
}
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {
if (!cursor.moveToPosition(position)) {
return;
}
String content = cursor.getString(cursor.getColumnIndex(DatabaseHandler.KEY_CONTENT));
Date date = Utilities.stringToDate(cursor.getString(cursor.getColumnIndex(DatabaseHandler.KEY_DEADLINE)));
int completed = cursor.getInt(cursor.getColumnIndex(DatabaseHandler.KEY_COMPLETED));
holder.tvContent.setText(content);
holder.tvDate.setText(Utilities.dateToString(date));
if(completed == 1){
holder.imgIcon.performClick();
}
}
@Override
public int getItemCount() {
return (cursor.getCount());
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView tvContent;
TextView tvDate;
ImageButton imgIcon;
public ViewHolder(@NonNull final View itemView) {
super(itemView);
tvContent = itemView.findViewById(R.id.tvContent);
tvDate = itemView.findViewById(R.id.tvDate);
imgIcon = itemView.findViewById(R.id.imgCheck);
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int position = getAdapterPosition();
cursor.move(position);
Note note = Utilities.cursorToNote(cursor);
Intent intent = new Intent(itemView.getContext(), AddNoteActivity.class);
intent.putExtras(note.sendNoteBundle());
intent.putExtra("type", true);
itemView.getContext().startActivity(intent);
}
});
}
}
}
这是在onActivityResult方法的第二个活动中创建Location对象的行
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)
Location.class
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
Trip.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;
}
在将其添加到父表之前，我看不到它是如何添加外键的。
答案 0 :(得分：0)
显示的代码似乎没有问题，那就是正在使用您的代码（为方便起见进行了少许修改（对于latLng来说很长，可以在主线程上运行）。
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());
}
（预期）结果：-
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
即存在TripId 1 ，并且已添加2个引用该Trip的位置。
就这样
我建议添加以下内容以进行调试：-
abstract TripDao tripDao();编码在@Database类中（以下使用AppDatabase）） ：-
@Query("SELECT * FROM trip_table")
List<Trip> getAllTrips();
Location location = new Location(tripId, locationName, locationLatLng);行之后和插入之前添加：-
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());
这将列出当前行程和要添加的位置。假设失败将是Trip ID和REFERENCES跳闸值之间的差异。如果Trip不如预期的那样存在，则由于某种原因，它不会被添加，否则将传递不正确的TripId。以上应该有助于确定哪个。