颤动：到期日期文本字段

Question

我们如何实现信用卡过期日期的文本字段格式化程序，如下所示MM/YY

Answer 1

17 天后，但我可以实现这个：

class CardExpirationFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue, TextEditingValue newValue) {
    final newValueString = newValue.text;
    String valueToReturn = '';

    for (int i = 0; i < newValueString.length; i++) {
      if (newValueString[i] != '/') valueToReturn += newValueString[i];
      var nonZeroIndex = i + 1;
      final contains = valueToReturn.contains(RegExp(r'\/'));
      if (nonZeroIndex % 2 == 0 &&
          nonZeroIndex != newValueString.length &&
          !(contains)) {
        valueToReturn += '/';
      }
    }
    return newValue.copyWith(
      text: valueToReturn,
      selection: TextSelection.fromPosition(
        TextPosition(offset: valueToReturn.length),
      ),
    );
  }
}