App freezes on cancel download

[abhinavsinghring]

I'm trying to download a file and show progress in a dialog and it contains cancel button. But when I try to click on cancel the button app freezes and I get an error and need to hot restart to open app again. Also complete file downloads.

This is the error

#0      CancelToken.cancel (package:dio/src/cancel_token.dart:42:43)
#1      Downloader.build.<anonymous closure>.<anonymous closure> (package:paperbook/Services/Downloader/downloader_dialog.dart:61:50)
#2      _InkResponseState.handleTap (package:flutter/src/material/ink_well.dart:1154:21)
#3      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:275:24)
#4      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:654:11)
#5      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:311:5)
#6      BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:244:7)
#7      PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:630:9)
#8      PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:98:12)
#9      PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:143:9)
#10     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:625:13)
#11     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:141:18)
#12     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:127:7)
#13     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:488:19)
#14     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:468:22)
#15     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:333:11)
#16     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:413:7)
#17     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:376:5)
#18     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:323:7)
#19     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:292:9)
#20     _invoke1 (dart:ui/hooks.dart:186:13)
#21     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:424:7)
#22     _dispatchPointerDataPacket (dart:ui/hooks.dart:119:31)
)

This is the downloader dialog code

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:paperbook/Constants/size_constant.dart';
import 'package:paperbook/Services/Downloader/Controller/downloader_controller.dart';
import 'package:paperbook/Widgets/SnackBar/snackbar_controller.dart';
import 'package:paperbook/Widgets/Text/custom_text.dart';

import '../../Screens/Downloads/download_screen.dart';

class Downloader extends StatelessWidget {
  const Downloader({
    super.key, 
    required this.docurl, 
    required this.doctitle,
    this.documentBytes
  });

  final String docurl, doctitle;
  final List<int>? documentBytes;

  @override
  Widget build(BuildContext context) {
    final DownloaderController downloaderController = Get.put(DownloaderController());
    final SnackBarController snackBarController = Get.put(SnackBarController());
    downloaderController.startDownloading(
      documentBytes,
      doctitle,
      docurl,
      context,
      snackBarController
    );
    return Obx(
      ()=> downloaderController.downloading.value? AlertDialog(
        clipBehavior: Clip.antiAlias,
        shape:  RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(20),
        ),
        backgroundColor: Theme.of(context).colorScheme.secondary,
        elevation: 0,
        contentPadding: EdgeInsets.all(mainpadding/2),
        content: Column(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            SizedBox(height: mainpadding),
            CircularProgressIndicator(color: Theme.of(context).colorScheme.primary, strokeWidth: 3,),
            SizedBox(height: mainpadding*1.5),
            TextWidget(
              text: "Downloading: ${downloaderController.progress}%",
              weight: FontWeight.w500,
              size: buttonSize
            ),
            TextButton(
              child: TextWidget(
                text: 'Cancel', 
                color: Theme.of(context).colorScheme.primary, 
                size: paraSize18,
                weight: FontWeight.w500,
              ),
              onPressed: () async {
                downloaderController.cancelToken.cancel('User cancelled download.');
                Get.back();
              },
            ),
          ],
        ),
      ) : 
      AlertDialog(
        clipBehavior: Clip.antiAlias,
        shape:  RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(20),
          ),
        backgroundColor: Theme.of(context).colorScheme.secondary,
        elevation: 0,
        title: TextWidget(
          text: 'Awesome! Your file has been downloaded.',
          size: buttonSize,
          weight: FontWeight.w500,
          center: true,
        ),
        actions: <Widget>[
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: [
              TextButton(
                child: TextWidget(
                  text: 'Go to Downloads', 
                  color: Theme.of(context).colorScheme.primary, 
                  size: paraSize18,
                  weight: FontWeight.w500,  
                ),
                onPressed: () async {
                  await Get.to(
                    () => const DownloadsPage(),
                    transition: Transition.cupertino,
                    duration: const Duration(milliseconds: 500),
                    popGesture: true,
                    gestureWidth: (context) {
                      double width =
                          MediaQuery.of(context).size.width;
                      return width;
                    },
                  );
                },
              ),
              TextButton(
                child: TextWidget(
                  text: 'Close', 
                  color: Theme.of(context).colorScheme.primary, 
                  size: paraSize18,
                  weight: FontWeight.w500,
                ),
                onPressed: () {
                  Get.back();
                },
              ),
            ],
          ),
        ],
      ),
    );
  }
}

And this is controller code

import 'package:dio/dio.dart';
import 'package:flutter/cupertino.dart';
import 'package:get/get.dart';
import 'package:paperbook/Screens/PdfReader/pdf_reader_screen.dart';
import 'package:paperbook/Widgets/SnackBar/content_type.dart';
import 'package:paperbook/Widgets/SnackBar/snackbar_controller.dart';
import 'package:path_provider/path_provider.dart';

class DownloaderController extends GetxController {
  static DownloaderController get instance => Get.find();

  var progress = '0'.obs;
  RxBool downloading = false.obs;
  final CancelToken cancelToken = CancelToken();

  Future<void> startDownloading(List<int>? documentBytes,String doctitle, String docurl, BuildContext context, SnackBarController snackBarController) async {

    downloading.value = true;

    final dir = await getApplicationDocumentsDirectory();                           
    // ignore: unnecessary_null_comparison
    if(dir != null){
      String savename = doctitle;
      String savePath = "${dir.path}/PaperBook/$savename.pdf";
    //   File file = File(savePath);
    //   //Write the PDF data retrieved from the SfPdfViewer.
    //   await file.writeAsBytes(documentBytes!, flush: true).then((value) {
    //       downloading.value = false;
    //       // interstitiaal advertisement
    //     }
    //   ).onError((error, stackTrace) {
    //     Get.back();
    //     snackBarController.showCustomSnackBar(
    //       "Error", 
    //       "Something went wrong!", 
    //       ContentTypeC.failure
    //     );
    // });

      try {
        await Dio().download(
          docurl, 
          savePath,
          onReceiveProgress: (received, total) {
            if (total != -1) {
              progress.value = ((received / total) * 100).toInt().toString();
            }
          },
          deleteOnError: true,
          cancelToken: cancelToken
        ).then((_) {
            downloading.value = false;
            Navigator.push(
              context,
              CupertinoPageRoute(
                builder: (context) => PdfReaderPage(
                  url: savePath, 
                  name: savename,
                  isFile: true,
                ),
              )
            );
            // interstitiaal advertisement
          },
        );       
      // ignore: unused_catch_clause
      } on DioError catch (e) {
        Get.back();
        snackBarController.showCustomSnackBar(
          "Error", 
          "Something went wrong!", 
          ContentTypeC.failure
        );
      }
    }    
  }
}

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