Android SQLite db.update() add values [duplicate]

Answer 1

The ContentValues object allows only simple values.

To do calculations, you have to write the SQL yourself and call execSQL:

public void Trasf() {
    SQLiteDatabase db = mHelper.getWritableDatabase();
    try {
        db.execSQL("UPDATE " + CTable.TABLE_NAME +
                   " SET " + CTable.PREL + " = " + CTable.PREL + " + ?" +
                   " WHERE " + CTable.NO + " = ?",
                   new Object[] { mI.getText().toString(),
                                  Scegli.getText().toString() });
    } finally {
        db.close();
    }
}