如何在不使用flutter中的setstate的情况下更新值？

import 'dart:io';

import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import 'package:nb_utils/nb_utils.dart';
import 'package:world_virtual_coin/widget/colors.dart';
import 'package:world_virtual_coin/widget/custom_text.dart';

class DioFileDownloader {
  final progressNotifier = ValueNotifier<double?>(0);
  static String statusValue = "0%";
  static dynamic totalValue;
  static dynamic receivedValue;
  static var dioObject = Dio();

  static Future download2(String url, String savePath) async {
    // dio = dioObject;
    try {
      Response response = await dioObject.get(
        url,
        onReceiveProgress: showDownloadProgress,
        //Received data with List<int>
        options: Options(
            responseType: ResponseType.bytes,
            followRedirects: false,
            validateStatus: (status) {
              return status! < 500;
            }),
      );
      print(response.headers);
      File file = File(savePath);
      var raf = file.openSync(mode: FileMode.write);
      // response.data is List<int> type
      raf.writeFromSync(response.data);
      await raf.close();
    } catch (e) {
      print(e);
    }
  }

  static Widget downloadStatus() {
    return Stack(
      alignment: Alignment.center,
      children: <Widget>[
        Align(
          alignment: Alignment.center,
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Container(
                decoration: BoxDecoration(
                  color: white,
                  borderRadius: BorderRadius.circular(10.r),
                ),
                margin: EdgeInsets.symmetric(horizontal: 20.w),
                padding: EdgeInsets.symmetric(horizontal: 10.w, vertical: 10.h),
                child: Row(
                  crossAxisAlignment: CrossAxisAlignment.center,
                  children: [
                    CustomText(
                      statusValue,
                      fontSize: 15,
                      isCentered: true,
                      textColor: const Color(0XFF161618),
                    ),
                    CustomText(
                      "Downloading",
                      fontSize: 15,
                      isCentered: true,
                      textColor: colorPrimary,
                    ),
                    30.height,
                  ],
                ),
              ),
            ],
          ),
        )
      ],
    );
  }

  static void showDownloadProgress(received, total) {
    totalValue = total;
    receivedValue = received;
    if (total != -1) {
      statusValue = ((received / total * 100).toStringAsFixed(0) + "%");

      print("DownloadStatus : " +
          (received / total * 100).toStringAsFixed(0) +
          "%");

      // statusUpdater();
    }
  }

}

DioFileDownloader类用于下载pdf文件。我在另一节课上用过

    CustomButton(
                              onPressed: () async {
                                // showDialog(
                                //     context: context,
                                //     builder: (context) => downloadStatus());
    
                                WidgetsBinding.instance
                                    .addPostFrameCallback((timeStamp) async {
                                  var tempDir = await getTemporaryDirectory();
                                  String fullPath = "${tempDir.path}/dummy.pdf'";
                                  print('full path $fullPath');
    
                                  File file = File(fullPath);
                                  if (await file.exists() && Platform.isAndroid) {
                                    OpenFile.open(file.path);
    
                                    // viewPdf();
                                  } else {
                                    DioFileDownloader.download2(imgUrl, fullPath);
                                  }
                                  setState(() {});
                                });
                              },
                              label: 'Save Pdf',
                            ),
   Row(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              CustomText(
                statusValue,
                fontSize: 15,
                isCentered: true,
                textColor: const Color(0XFF161618),
              ),
              CustomText(
                " Downloading",
                fontSize: 15,
                isCentered: true,
                textColor: colorPrimary,
              ),
              30.height,
            ],
          ),

当前，下载状态正在工作，但点击自定义按钮时，它不会显示在视图侧。这就是状态值。基本设置状态不工作。如何更新视图状态。

我的意思是下载文件的百分比。。。

以下描述，

在出版和平面设计中，Lorem ipsum是一种占位符文本，通常用于演示文档或字体的视觉形式，而不依赖于有意义的内容。Lorem ipsum可在最终副本可用之前用作占位符。