FOREIGN KEY constraint failed (code 787) in Room database

Question

I'm trying to learn relations in the Room database, but I have some problem. I want to put Expense to Date, but app crashes and logcat shows this: Caused by: android.database.sqlite.SQLiteConstraintException: FOREIGN KEY constraint failed (code 787). The classes are pasted without setters and getters.

Date:

@Entity(tableName = "dates")
public class Date {

@PrimaryKey(autoGenerate = true)
private int id;
private Long dateLong = System.currentTimeMillis();
private String date = new SimpleDateFormat("MM/yyyy").format(new java.util.Date(dateLong));

private int month;
private int week;
private int day;
private int dayOfWeek;
private String weekDay

public Date(int month, int week, int day, int dayOfWeek, String weekDay) {
    this.month = month;
    this.week = week;
    this.day = day;
    this.dayOfWeek = dayOfWeek;
    this.weekDay = weekDay;
}

Expense:

@Entity(tableName = "expense_table",
    foreignKeys = @ForeignKey(entity = com.example.test.Date.class,
    parentColumns = "id",
    childColumns = "dateId",
            onDelete = CASCADE),
    indices = @Index("dateId"))
public class Expense {

@PrimaryKey(autoGenerate = true)
private int id;
private int dateId;
private String note;
private Double value;
private String type;

public Expense(Double value, String note, String type) {
    this.value = value;
    this.note = note;
    this.type = type;
}

Answer 1

you need to create first date table entry than add expense entry to database. for more information visit this link