尝试更新android中的sqlite数据库时出错

Question

我有我的数据库工作，但我插入的所有记录都是为了检查目的，现在我想删除所有表并创建新的，所以我试图通过更改数据库更新版本。

我没有改变任何创建表查询，但我得到一个外键约束失败（代码787）。

这里是我DBHelper类：

private static final String DATABASE_NAME = "roomatesDB"; 
    // database version 
    private static final int DATABASE_VERSION = 3; 

    // tables name 
    public static final String APARTMENT_TABLE = "apartment"; 
    public static final String ROOMATE_TABLE = "roomate"; 
    public static final String SHOPCART_TABLE = "shopcart"; 
    public static final String ITEMS_TABLE = "items"; 

    // common column 
    public static final String APARTMENT_NUMBER_COLUMN = "apartmentNum"; 

    // roomates table columns 
    public static final String FIRST_NAME_COLUMN = "firstName"; 
    public static final String LAST_NAME_COLUMN = "lastName"; 
    public static final String PHONE_NUMBER_COLUMN = "phoneNumber"; 

    // shop cart table columns 
    public static final String NUMBER_COLUMN = "number"; 
    public static final String LIST_NAME_COLUMN = "name"; 

    // item table 
    public static final String PRICE_COLUMN = "price"; 
    public static final String ITEM_NAME_COLUMN = "name"; 

    // query for creating roomate table 
    public static final String CREATE_ROOMATE_TABLE = "CREATE TABLE " 
      + ROOMATE_TABLE + "(" + FIRST_NAME_COLUMN + " TEXT, " 
      + LAST_NAME_COLUMN + " TEXT, " + PHONE_NUMBER_COLUMN + " TEXT, " 
      + APARTMENT_NUMBER_COLUMN + " INTEGER, " 
      + "FOREIGN KEY(" + APARTMENT_NUMBER_COLUMN + ") REFERENCES " 
      + APARTMENT_TABLE + "(apartmentNum) " + ")"; 

    // query for crating shop cart table 
    public static final String CREATE_SHOPLIST_TABLE = "CREATE TABLE " 
      + SHOPCART_TABLE + "(" + NUMBER_COLUMN + " INTEGER PRIMARY KEY," 
      + LIST_NAME_COLUMN + " TEXT, " 
      + APARTMENT_NUMBER_COLUMN + " INTEGER, " 
      + "FOREIGN KEY(" + APARTMENT_NUMBER_COLUMN + ") REFERENCES " 
      + APARTMENT_TABLE + "(apartmentNum) " + ")"; 

    // query for creating shop item table 
    public static final String CREATE_SHOPITEM_TABLE = "CREATE TABLE " 
      + ITEMS_TABLE + "(" + ITEM_NAME_COLUMN + " TEXT," 
      + PRICE_COLUMN + " DOUBLE, " 
      + NUMBER_COLUMN + " INT, " 
      + "FOREIGN KEY(" + NUMBER_COLUMN + ") REFERENCES " 
      + SHOPCART_TABLE + "(number) " + ")"; 

    // query for creating apartment table 
    public static final String CREATE_APARTMENT_TABLE = "CREATE TABLE " 
      + APARTMENT_TABLE + "(" + APARTMENT_NUMBER_COLUMN + " INTEGER PRIMARY KEY" 
      + ")"; 


    public DBHelper(Context context) { 
     super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    } 

    public void onConfigure(SQLiteDatabase db) { 
     super.onConfigure(db); 
     db.setForeignKeyConstraintsEnabled(true); 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     db.execSQL(CREATE_APARTMENT_TABLE); 
     db.execSQL(CREATE_ROOMATE_TABLE); 
     db.execSQL(CREATE_SHOPLIST_TABLE); 
     db.execSQL(CREATE_SHOPITEM_TABLE); 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     db.execSQL("DROP TABLE IF EXISTS " + APARTMENT_TABLE); 
     db.execSQL("DROP TABLE IF EXISTS " + ROOMATE_TABLE); 
     db.execSQL("DROP TABLE IF EXISTS " + SHOPCART_TABLE); 
     db.execSQL("DROP TABLE IF EXISTS " + ITEMS_TABLE); 

     onCreate(db); 

    } 

Answer 1

的documentation说：

如果外键约束启用时，DROP TABLE命令执行从删除表之前的隐式DELETE FROM指令数据库模式。 [...]如果作为DROP TABLE命令的一部分执行的隐式DELETE FROM违反了任何即时外键约束，则会返回错误并且不会删除该表。

以正确的顺序删除数据，以便所有中间步骤都有效。或者只是禁用外部约束检查（db.setForeignKeyConstraintsEnabled()）。