Android ROOM：当输入新数据时，我得到FOREIGN KEY约束失败（代码787SQLITE_CONSTRAINT_FOREIGNKEY）

Question

我知道很多人问过这个外键约束失败（代码787 SQLITE_constraint_FOREIGNKEY）错误，但我的问题略有不同。我有两个实体学生和记录。我可以添加学生，但是当我为该学生添加相应的记录时，我得到了这个错误。首先添加学生详细信息，然后添加学生记录详细信息。

学生POJO班

@Entity(tableName = "student_table")
public class Student {
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "student_id")
    private int id;

    private String studentName;

    private String studentFatherName;

    private String studentSurname;

记录POJO类

    @Entity(tableName = "newRecord_table", indices = @Index("recordId"),
            foreignKeys = @ForeignKey(entity = Student.class, parentColumns = "student_id",childColumns = "recordId",
                    onDelete = ForeignKey.CASCADE, onUpdate = ForeignKey.CASCADE))

    public class NewRecord {

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

        public int recordId;
        public string address;
        public string mobile;

学生道班

@Dao
public interface StudentDAO {

    @Insert(onConflict = REPLACE)
    void addStudent (Student student);

    @Update
    void updateStudent (Student student);

    @Delete
    void deleteStudent (Student student);

    @Query("SELECT * FROM student_table ORDER BY studentName ASC")
    LiveData<List<Student>> getAllStudents();

    @Query("DELETE FROM student_table")
    void deleteAllStudents();
}

记录道类

@Dao
public interface NewRecordDAO {

    @Insert(onConflict = REPLACE)
    public void addRecord (NewRecord newRecord);

    @Update(onConflict = REPLACE)
    public void updateRecord (NewRecord newRecord);

    @Delete
    public void deleteRecord (NewRecord newRecord);

    @Query("DELETE FROM newRecord_table")
    void deleteAllRecords();

    @Query("SELECT * FROM newRecord_table ORDER BY NRdate DESC")
    LiveData<List<NewRecord>> getAllRecord();
}

学生知识库课程

public class StudentRepository {
    private StudentDAO studentDAO;
    private LiveData<List<Student>> allStudents;

    public StudentRepository (Application application){
        StudentDatabase database = StudentDatabase.getInstance(application);
        studentDAO = database.studentDAO();
        allStudents = studentDAO.getAllStudents();
    }
     public void addStudent (Student student){
        new addStudentAsyncTask(studentDAO).execute(student);

     }
 public static class addStudentAsyncTask extends AsyncTask <Student,Void,Void>{
        private StudentDAO studentDAO;
        private addStudentAsyncTask (StudentDAO studentDAO){
            this.studentDAO = studentDAO;
        }
        @Override
        protected Void doInBackground(Student... students) {
            studentDAO.addStudent(students[0]);
            return null;
        }
    }

记录存储库类

public class NewRecordRepository {

    private NewRecordDAO newRecordDAO;
    private LiveData<List<NewRecord>> allRecords;
    private LiveData<List<NewRecord>> allRecordByStudent;

    public NewRecordRepository (Application application){
        StudentDatabase database = StudentDatabase.getInstance(application);
        newRecordDAO = database.newRecordDAO();
        allRecords = newRecordDAO.getAllRecord();

    }

    public void addRecord (NewRecord newRecord){
        new addRecordAsyncTask(newRecordDAO).execute(newRecord);
    }
 public static class addRecordAsyncTask extends AsyncTask<NewRecord,Void,Void> {
        private NewRecordDAO newRecordDAO;
        private addRecordAsyncTask (NewRecordDAO newRecordDAO){
            this.newRecordDAO = newRecordDAO;
        }
        @Override
        protected Void doInBackground(NewRecord... newRecords) {

// LOG shows: this is where it re direct me this is where the problem lies.
            newRecordDAO.addRecord(newRecords[0]);
            return null;
        }
    }

最后是数据库类

@Database(entities = {Student.class, NewRecord.class}, version = 1, exportSchema = false)
public abstract class StudentDatabase extends RoomDatabase {

    private static StudentDatabase instance;

    public abstract StudentDAO studentDAO();

    public abstract NewRecordDAO newRecordDAO();

    public static synchronized StudentDatabase getInstance(Context context){
        if ( instance == null ){
            instance = Room.databaseBuilder(context.getApplicationContext(),
                    StudentDatabase.class,"students_DB")
                    .fallbackToDestructiveMigration()
                    .build();
        }
        return instance;
    }

我的日志：

E/AndroidRuntime:致命异常：AsyncTask#4进程：com。永恒的融合。hifztasmee，PID:12833 java。lang.RuntimeException:在android上执行doInBackground（）时出错。操作系统。3美元。在java上完成（AsyncTask.java:354）。util。同时发生的未来任务。在java完成（FutureTask.java:383）。util。同时发生的未来任务。java上的setException（FutureTask.java:252）。util。同时发生的未来任务。在android上运行（FutureTask.java:271）。操作系统。AsyncTask$SerialExecutor$1。在java上运行（AsyncTask.java:245）。util。同时发生的线程池执行器。java上的runWorker（ThreadPoolExecutor.java:1167）。util。同时发生的ThreadPoolExecutor$Worker。在java上运行（ThreadPoolExecutor.java:641）。朗。丝线。运行（Thread.java:764）的原因是：android。数据库sqlite。SQLiteConstraintException:android上的外键约束失败（代码787 SQLITE_constraint_FOREIGNKEY）。数据库sqlite。SQLiteConnection。android上的nativeExecuteForLastInsertedRowId（本机方法）。数据库sqlite。SQLiteConnection。android上的executeForLastInsertedRowId（SQLiteConnection.java:796）。数据库sqlite。SQLiteSession。android上的executeForLastInsertedRowId（SQLiteSession.java:788）。数据库sqlite。SQLITE声明。androidx上的executeInsert（SQLiteStatement.java:86）。sqlite。db。框架FrameworkSQLiteStatement。androidx上的executeInsert（FrameworkSQLiteStatement.java:51）。房间EntityInsertionAdapter。在com上插入（EntityInsertionAdapter.java:64）。永恒的融合。你好。多阿。新记录。addRecord（NewRecordDAO_Impl.java:242）位于com。永恒的融合。你好。存储库。NewRecordRepository$addRecordAsyncTask。doInBackground（NewRecordRepository.java:61）位于com。永恒的融合。你好。存储库。NewRecordRepository$addRecordAsyncTask。doInBackground（NewRecordRepository.java:54）

Answer 1

调用addRecordnewRecord对象时，需要为已添加的学生id设置recordid。

如果有

    NewRecord n1 = new NewRecord();

    n1.address = "xxx";
    n1.mobile = "0000000000";
    n1.NRDate = "2020-01-01 10:30";
    newRecordRepository.addRecord(n1);

失败就像

Caused by: android.database.sqlite.SQLiteConstraintException: FOREIGN KEY constraint failed (code 787 SQLITE_CONSTRAINT_FOREIGNKEY)

更改以提供适当的recordId，如

    NewRecord n1 = new NewRecord();
    n1.recordId = 1;
    n1.address = "xxx";
    n1.mobile = "0000000000";
    n1.NRDate = "2020-01-01 10:30";
    newRecordRepository.addRecord(n1);

1可以显示测试，你需要适当的学生当做真正的