java - 如何从SQLite到具有自定义对象的模型的行？

我正在努力从SQLite中获得一席之地。

这是我的DatabaseHelper片段：

public Expense getExpense(long id) {

        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(EXPENSE_TABLE_NAME,
                new String[]{EXPENSE_COLUMN_ID, EXPENSE_COLUMN_TYPE, EXPENSE_COLUMN_PERSON_IN_DEBT, EXPENSE_COLUMN_AMOUNT,
                        EXPENSE_COLUMN_DESCRIPTION, EXPENSE_COLUMN_TIMESTAMP, EXPENSE_COLUMN_IS_PAID},
                EXPENSE_COLUMN_ID + "=?",
                new String[]{String.valueOf(id)}, null, null, null, null);

        if (cursor != null)
            cursor.moveToFirst();

        assert cursor != null;
        Expense expense = new Expense(
                cursor.getInt(cursor.getColumnIndex(EXPENSE_COLUMN_ID)),
  ERROR HERE -> (ExpenseType)cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_TYPE)),
  ERROR HERE -> (Person)cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_PERSON_IN_DEBT)),
                cursor.getDouble(cursor.getColumnIndex(EXPENSE_COLUMN_AMOUNT)),
                cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_DESCRIPTION)),
                cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_TIMESTAMP)),
                cursor.getInt(cursor.getColumnIndex(EXPENSE_COLUMN_IS_PAID))); // true for 1

        cursor.close();
        db.close();
        return expense;
    }

Expense模型中的构造函数如下所示：

public Expense(int id, ExpenseType expenseType, Person person, Double amount, String description, String timestamp, int isPaid).

我在上面标记为错误的行上遇到了强制转换错误


“不可转换类型；无法将'java.lang.String'强制转换为'
com ... model.ExpenseType“


我该如何进行这项工作？在数据库中，对象expenseType和person作为字符串添加。

最佳答案

这些行：

(ExpenseType)cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_TYPE)),
(Person)cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_PERSON_IN_DEBT))

您尝试将2个字符串强制转换为ExpenseType类型的对象和Person类型的对象，但无法完成。
您没有发布类ExpenseType和Person，所以我不知道它们的构造函数，但是如果它们的构造函数将字符串作为参数，也许您可​​以这样做：

new ExpenseType(cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_TYPE))),
new Person(cursor.getString(cursor.getColumnIndex(EXPENSE_COLUMN_PERSON_IN_DEBT)))