Flutter Textfield capture dollar amount and apply a fee

Question

We have a flutter text field whereby a user can enter an amount as an int, and what we want to do is that int calculated an amount less a fee. Probably is I cannot work out here what I am doing wrong

TextFormField(
                          controller: _offerAmountController,
                          textInputAction: TextInputAction.next,
                          decoration: const InputDecoration(
                            hintText: '5-9999',
                            prefixIcon: Icon(Icons.attach_money_rounded),
                            // labelText: 'Your Offer',
                          ),
                          keyboardType: TextInputType.number,
                          onChanged: (offerAmount) {
                            
                            double sum = int.parse(offerAmount) * 0.1;
                            _offer = sum as int;
                          }),

Text(formatCurrency.format(_offer),
                                style: Theme.of(context)
                                    .textTheme
                                    .headlineSmall
                                    .copyWith(color: Colors.blue[700]))

final formatCurrency =
    NumberFormat.simpleCurrency(locale: 'en_AU', decimalDigits: 0);

Answer 1

Try this:

setState(() {
  _offer = sum.toInt();
});