Flutter TextField with number input type

number_textfield_example.dart

bool _numberInputIsValid = true;

  Widget _buildNumberTextField() {
    return TextField(
      keyboardType: TextInputType.number,
      style: Theme.of(context).textTheme.display1,
      decoration: InputDecoration(
        icon: Icon(Icons.attach_money),
        labelText: 'Enter an integer:',
        errorText: _numberInputIsValid ? null : 'Please enter an integer!',
        border: OutlineInputBorder(
          borderRadius: BorderRadius.all(Radius.circular(10.0)),
        ),
      ),
      onSubmitted: (val) =>
          Fluttertoast.showToast(msg: 'You entered: ${int.parse(val)}'),
      onChanged: (String val) {
        final v = int.tryParse(val);
        debugPrint('parsed value = $v');
        if (v == null) {
          setState(() => _numberInputIsValid = false);
        } else {
          setState(() => _numberInputIsValid = true);
        }
      },
    );
  }