"Cannot run with sound null safety" Flutter an existing Project?

Question

I had an existing application which i want to modify, I am using following dependencies:

  path_provider: ^2.0.8
  http: ^0.13.4
  html: ^0.15.0
  custom_pop_up_menu: ^1.2.2
  share: ^2.0.4
  connectivity: ^3.0.6
  flutter_swiper: ^1.1.6

Following error, i have even created a new empty project and added the dart files to that project but it is not working now.

    Error: Cannot run with sound null safety, because the following dependencies
don't support null safety:

 - package:flutter_swiper
 - package:plugin_platform_interface
 - package:flutter_page_indicator
 - package:transformer_page_view

Answer 1

This is because some of the dependencies that you are using not supports null-safety and to solve this you can upgrade your dependencies or use below command to run your application without null-safety.

flutter run --no-sound-null-safety

Answer 2

First upgrade your flutter and packages upto date,

1. Run flutter pub outdated --mode=null-safety to print all outdated packages. Than,
2. Run this, flutter pub upgrade --null-safety to upgrade all packages automatically

Answer 3

Option 1: Upgrade your flutter and packages upto date Run flutter pub outdated --mode=null-safety to display all outdated packages. Then, Run flutter pub upgrade --null-safety to upgrade all packages with no sound null safety

Option 2: Run flutter run --no-sound-null-safety

Option 3: If you want to run your applications with no sound null safety, For VSCode user, add below to settings.json

"dart.flutterRunAdditionalArgs": [
    "--no-sound-null-safety"
],