How To Check Cursor Null Or Not In Android?

I'm trying to check values of field ID in BangCauHoi table. This is my function: public boolean checkID(String ndCauHoi){ boolean check = true; String query = 'sele

Solution 1:

You can check to see whether or not it is empty with the following statement:

if (c.moveTofirst() && c.getCount > 0)

or

if(c!=null&&c.moveToFirst())

As to why it is empty, I would guess that you have mistyped a statement somewhere. I always use the querymethod in the SQLiteDatabase class instead of rawQuery, and use constants for my column names instead of hardcoding them to try and avoid these problems.

publicstaticfinalString KEY_ID = "_id";
publicstaticfinalString TABLE_NAME="BangCauHoi";
publicstaticfinalString CAUHOI = "CauHoi";

Cursor c = yourDatabaseInstance.getReadabledatabase().query(
    YourDatabaseName.TABLE_NAME, 
    newString[] { YourDatabaseName.KEY_ID },
    YourDatabaseName.CAUHOI + "=?", 
    newString[] { ndCauHoi }, 
    null, null, null);

Solution 2:

Your database does not have any rows mathing the selection and moveToFirst() returns false. When unchecked, you'll get the exception about trying to retrieve values from a nonexisting row. When checked, it returns the default value true you've specified.