Flutter 身份证号格式化输入

如上图，此类需求，身份证号码输入需要格式处理

import 'package:flutter/material.dart';

class CardIdItem extends StatefulWidget {
  const CardIdItem({Key? key}) : super(key: key);

  @override
  State<CardIdItem> createState() => _CardIdItemState();
}

class _CardIdItemState extends State<CardIdItem> {

  final TextEditingController codeEdit = TextEditingController();

  String _oldInputCodeText = "";

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: const EdgeInsets.all( 20),
      height: 56,
      // color: Colors.blueAccent,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: <Widget>[
           Container(
            width: 70,
            height: 30,
            alignment: Alignment.centerLeft,
            child: const Text(
              "身份证",
              style: TextStyle(
                  fontSize: 16),
            ),
          ),
          Flexible(
            child: TextField(
              controller: codeEdit,
              keyboardType:  const TextInputType.numberWithOptions(signed: true),
              maxLength: 21,
              obscureText:  false,
              onChanged: (value) {
                _splitPhoneNumber(value);
              },
              style: const TextStyle(fontSize: 16),
              decoration: const InputDecoration(
                // contentPadding: EdgeInsets.only(top: 4.px),
                counterText: "", //此处控制最大字符是否显示
                hintText: "请输入身份证",
                hintStyle: TextStyle(color: Colors.grey),
                enabledBorder: UnderlineInputBorder(
                    borderSide: BorderSide(color: Colors.grey)),
                focusedBorder: UnderlineInputBorder(
                    borderSide: BorderSide(color: Colors.grey)),
              ),
            ),
          ),
        ],
      ),
    );
  }


  void _splitPhoneNumber(String text) {
    //输入身份证号格式
    String codeText = getIdCode(text); //去除空格
    //记录此时光标位置
    int currentSelection = codeEdit.selection.base.offset;

    //删除空格，相当于删除空格前一位
    if (_oldInputCodeText.length > text.length &&
        codeText.isNotEmpty &&
        _oldInputCodeText.substring(currentSelection, currentSelection + 1) ==
            " ") {
      String oldStartString =
      _oldInputCodeText.substring(0, currentSelection + 1);
      //定位删除空格位置
      oldStartString = getIdCode(oldStartString);
      codeText = codeText.replaceRange(
          oldStartString.length - 1, oldStartString.length, "");
    }

    String newCodeText = "";
    for (int index = 0; index < codeText.length; index++) {
      if (index == 5 || index == 9 || index == 13) {
        newCodeText = "$newCodeText${codeText[index]} ";
      } else {
        newCodeText = newCodeText + codeText[index];
      }
    }

    _oldInputCodeText = newCodeText;
    codeEdit.text = newCodeText;
    if (newCodeText.length > text.length) {
      currentSelection = currentSelection + 1;
    } else if (newCodeText.length < text.length) {
      currentSelection = currentSelection - 1;
    }
    //设置光标位置
    codeEdit.selection = TextSelection.fromPosition(TextPosition(
        affinity: TextAffinity.downstream, offset: currentSelection));
  }

  String getIdCode(String text) {
    return text.replaceAll(RegExp(r"\s+\b|\b\s"), "");
  }
}