Android开发7——android.database.CursorIndexOutOfBoundsException:Index -1 requested, with a size of 1

android中数据库处理使用cursor时，游标不是放在为0的下标，而是放在为-1的下标处开始的。

也就是说返回给cursor查询结果时，不能够马上从cursor中提取值。

下面的代码会返回错误

User u = null;SQLiteDatabase db = dbHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select * from user where id = ?", new String[] { id.toString() });Integer uid = cursor.getInt(cursor.getColumnIndex("id"));String uname = cursor.getString(cursor.getColumnIndex("name"));float uamount = cursor.getFloat(cursor.getColumnIndex("amount"));u = new User(uid, uname, uamount);cursor.close();

正确的用法

User u = null;SQLiteDatabase db = dbHelper.getReadableDatabase();Cursor cursor = db.rawQuery("select * from user where id = ?", new String[] { id.toString() });if (cursor.moveToFirst()){ Integer uid = cursor.getInt(cursor.getColumnIndex("id")); String uname = cursor.getString(cursor.getColumnIndex("name")); float uamount = cursor.getFloat(cursor.getColumnIndex("amount")); u = new User(uid, uname, uamount);}cursor.close();