Android android.database.CursorIndexOutOfBoundsException:Index -1 requested, with a size of 1 _exception

古之立大事者，不惟有超世之才，亦必有坚忍不拔之志。这篇文章主要讲述Android android.database.CursorIndexOutOfBoundsException:Index -1 requested, with a size of 1相关的知识，希望能为你提供帮助。
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();

【Android android.database.CursorIndexOutOfBoundsException:Index -1 requested, with a size of 1】