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Android 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();  

 

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