Why I get Flutter mistake screen(red screen) when using CupertinoNavigationBarBackButton?

Question

This is the problem that I got => The following assertion was thrown building CupertinoNavigationBarBackButton(dirty, dependencies: [_ModalScopeStatus]): CupertinoNavigationBarBackButton should only be used in routes that can be popped 'package:flutter/src/cupertino/nav_bar.dart': Failed assertion: line 1333 pos 9: 'currentRoute?.canPop == true'

I really do not understand this situation because I used previous 2 pages there is no problem but last page made problem.

Here is my related code part:(third page)

 @override
  Widget build(BuildContext context) {
    final name = basename(widget.file!.path);
    if(Platform.isIOS){
      return CupertinoPageScaffold(
        navigationBar: CupertinoNavigationBar(
          leading: CupertinoNavigationBarBackButton(
            color: CupertinoColors.white,
          ),

This is he way how to come here: (first page)

CupertinoButton(
   padding: EdgeInsets.all(0),
   child: Icon(CupertinoIcons.list_bullet, color: CupertinoColors.white,),
   onPressed: () => {
      Navigator.push(context, CupertinoPageRoute(builder: (context) => ConsumptionReportsScreen(location: widget.location)))
   }
),

(second page)

onTap: () async {
   // final file = await PDFApi.loadNetwork(reports[index].pdfUrl);
   const url = 'https://www.adobe.com/support/products/enterprise/knowledgecenter/media/c4611_sample_explain.pdf';
   final file = await PDFApi().loadNetwork(url);
   Navigator.push(context, CupertinoPageRoute(builder: (context) => PdfViewerScreen(file: file)));
  },

score 0 · Answer 1 · answered Mar 30 '22 at 08:42

0

The error you're getting shows that the page you're currently on can't be popped.

Failed assertion: line 1333 pos 9: 'currentRoute?.canPop == true'

Are you sure there are pages in the stack that can be popped to?

answered Mar 30 '22 at 08:42

Advait

574
3
12

It is opening, I cannot show you right now but i can navigate. There is only problem that back button place in navigation bar turns red screen first then it is closing. Although it is closing, firstly red screen is a problem. I do not know how to fix it – theredboy Mar 30 '22 at 08:48
Can you add the code for how you come to this page, it'll be somewhat like `Navigator.push` or something, and also add the code for how you're popping these pages. – Advait Mar 30 '22 at 08:51
Im going to add right now – theredboy Mar 30 '22 at 08:54
I have added the way, you can see from the question @Advait – theredboy Mar 30 '22 at 09:02

score 0 · Answer 2 · edited Mar 30 '22 at 09:05

first return a material app and in and inside it use CupertionoPageScaffold() as home page , i hope this will help

    import 'dart:io';

    import 'package:flutter/cupertino.dart';
    import 'package:flutter/material.dart';

    void main() => runApp(MyApp());

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

      @override
       State<MyApp> createState() => _MyAppState();
    }

    class _MyAppState extends State<MyApp> {
      @override
      Widget build(BuildContext context) {
      if(Platform.isIOS){
       return MaterialApp(
        home: CupertinoPageScaffold(
          child: Container(),
        ),
      );
     }else {
      return MaterialApp(
        home: Scaffold(),
      );
     }
    }
   }

when you give the answer that time please add output (image or gif file) so user can much better understand — MohammedAli, Mar 30 '22 at 09:18

Ravindra S. Patil · Answer 3 · 2022-03-30T09:12:39.080

0

Try below code, I have try other way

CupertinoPageScaffold(
  navigationBar: CupertinoNavigationBar(
    backgroundColor: CupertinoColors.activeGreen,
    middle: const Text('Sample Code'),
    leading: GestureDetector(
      onTap: () {
        print('Button Pressed');
        Navigator.of(context).pop();
      },
      child: Icon(
        CupertinoIcons.left_chevron,
        color: CupertinoColors.white,
      ),
    ),
  ),
  child: Container(),
),

Result screen->

edited Mar 30 '22 at 09:12

answered Mar 30 '22 at 09:05

Ravindra S. Patil

11,757
3
13
40

Thank you but when i add onpressed and navigator.pop it gives me mistake – theredboy Mar 30 '22 at 09:08
I have update the code please check – Ravindra S. Patil Mar 30 '22 at 09:13
I tried that before as a CupertinoButton. And i tried yours it is not working – theredboy Mar 30 '22 at 10:22
its working for me – Ravindra S. Patil Mar 30 '22 at 10:23
How you pass to this page? Could you send me it – theredboy Mar 30 '22 at 10:25
you can test my code on [dartpad](https://dartpad.dev/?null_safety=true) and pressed the arrow button the page is exit – Ravindra S. Patil Mar 30 '22 at 10:29
You dont understand me. Im trusting you that it is working but in my example it is not working. I want to work that but it is not working on my structure – theredboy Mar 30 '22 at 10:32
Also i can do this in not complex example. – theredboy Mar 30 '22 at 10:33

Why I get Flutter mistake screen(red screen) when using CupertinoNavigationBarBackButton?

3 Answers3