Flutter inputformatter for date

Question

我正在寻找一个文本字段的inputformatter的例子，它将是一个日期mm / dd / yyyy，我正在尝试做的事情，因为用户类型更新格式。例如，用户开始输入mm并输入/，然后在输入/中键入dd时。

任何人都这样做或有一个例子？我用其他语言做过但在flutter / dart中找不到类似的方法。

这是我到目前为止所尝试的，但无法使逻辑正确。有什么想法吗？

    class _DateFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue,
      TextEditingValue newValue
      ) {
    final int newTextLength = newValue.text.length;
    int selectionIndex = newValue.selection.end;
    int usedSubstringIndex = 0;
    final StringBuffer newText = new StringBuffer();
    if (newTextLength == 2) {
      newText.write(newValue.text.substring(0, 2) + '/ ');
      if (newValue.selection.end == 3)
        selectionIndex+=3;
    }
    if (newTextLength == 5) {
      newText.write(newValue.text.substring(0, 5) + '/ ');
      if (newValue.selection.end == 6)
        selectionIndex += 6;
    }
    // Dump the rest.
    if (newTextLength >= usedSubstringIndex)
      newText.write(newValue.text.substring(usedSubstringIndex));
    return new TextEditingValue(
      text: newText.toString(),
      selection: new TextSelection.collapsed(offset: selectionIndex),
    );
  }
}

由于

Answer 1

这是基于Jochem Toolenaar回答的改进版本。此版本将自动为您删除正斜杠并将用户限制为8位数字。

class DateTextFormatter extends TextInputFormatter {
  static const _maxChars = 8;

  @override
  TextEditingValue formatEditUpdate(
      TextEditingValue oldValue, TextEditingValue newValue) {
    var text = _format(newValue.text, '/');
    return newValue.copyWith(text: text, selection: updateCursorPosition(text));
  }

  String _format(String value, String seperator) {
    value = value.replaceAll(seperator, '');
    var newString = '';

    for (int i = 0; i < min(value.length, _maxChars); i++) {
      newString += value[i];
      if ((i == 1 || i == 3) && i != value.length - 1) {
        newString += seperator;
      }
    }

    return newString;
  }

  TextSelection updateCursorPosition(String text) {
    return TextSelection.fromPosition(TextPosition(offset: text.length));
  }
}

Answer 2

我也在为此苦苦挣扎。我得到了以下不太好用的解决方案：

class DateInputTextField extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _DateInputTextFieldState();
  }
}

class _DateInputTextFieldState extends State<DateInputTextField> {
  @override
  Widget build(BuildContext context) {
    return TextField(
      keyboardType: TextInputType.number,
      inputFormatters: [DateTextFormatter()],
      onChanged: (String value) {},
    );
  }
}

class DateTextFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {

    //this fixes backspace bug
    if (oldValue.text.length >= newValue.text.length) {
      return newValue;
    }

    var dateText = _addSeperators(newValue.text, '/');
    return newValue.copyWith(text: dateText, selection: updateCursorPosition(dateText));
  }

  String _addSeperators(String value, String seperator) {
    value = value.replaceAll('/', '');
    var newString = '';
    for (int i = 0; i < value.length; i++) {
      newString += value[i];
      if (i == 1) {
        newString += seperator;
      }
      if (i == 3) {
        newString += seperator;
      }
    }
    return newString;
  }

  TextSelection updateCursorPosition(String text) {
    return TextSelection.fromPosition(TextPosition(offset: text.length));
  }
}

Answer 3

class DateFormatter extends TextInputFormatter {
    @override
    TextEditingValue formatEditUpdate(
        TextEditingValue oldValue,
        TextEditingValue newValue
        ) {
      final int newTextLength = newValue.text.length;
      int selectionIndex = newValue.selection.end;
      int usedSubstringIndex = 0;
      final StringBuffer newText = StringBuffer();
      if (newTextLength >= 3) {
        newText.write(newValue.text.substring(0, usedSubstringIndex = 2) + '/');
        if (newValue.selection.end >= 2)
          selectionIndex++;
      }
      if (newTextLength >= 5) {
        newText.write(newValue.text.substring(2, usedSubstringIndex = 4) + '/');
        if (newValue.selection.end >= 4)
          selectionIndex++;
      }

      // Dump the rest.
      if (newTextLength >= usedSubstringIndex)
        newText.write(newValue.text.substring(usedSubstringIndex));
      return TextEditingValue(`enter code here`
        text: newText.toString(),
        selection: TextSelection.collapsed(offset: selectionIndex),
      );
    }