Android programming help

Anyone help me?

Stackoverflow seems so condescending, not a place for a noob. I've asked on another group but it doesn't seem a busy group. Clutching straws with Chit Chat but surely someone has a bit of programming knowledge.

I'm trying to pass a date into a String via a method but I keep returning a null value.

        getDateTime();  // this keeps returning null
        balanceToDatabase(balance, strId);
        helper.insertIntoPaid(strId, amountpaid, dateTime, "Notes Paid", "Spare 1", "Spare 2", "Spare 3"); //insert into paid table


        btnPaid.setClickable(false); // so paid button can't be pressed again to avoid mistakes

        Toast.makeText((getApplicationContext()), "£" + amountpaid + " paid has been recorded!", Toast.LENGTH_SHORT).show();
    }

        public void balanceToDatabase (String amountResultStr, String strId){
        ContentValues newValues = new ContentValues();
        newValues.put("balance", amountResultStr);
        SQLiteDatabase db= helper.getWritableDatabase();
        db.update("customers", newValues, "_id="+ strId, null);
        db.close();
    }

        public String getDateTime() {
            Calendar c = Calendar.getInstance();

            SimpleDateFormat df = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
            String dateTime = df.format(c.getTime());
            // formattedDate have current date/time
            Toast.makeText(this, dateTime, Toast.LENGTH_SHORT).show();  // This is showing the date time when button clicked

            return dateTime;
        }