I am building a Flutter app and I need to use the flutter_redux package for my global state management.
Unfortunately when I added it and try to execute my app I am getting the below error:
Error: Cannot run with sound null safety, because the following dependencies
don't support null safety:
- package:redux
- package:flutter_redux
Please, how can I resolve this?
// #dart=2.9 - add this as is to the top of main.dart file
Alternatively, set the language version in the entrypoint — the file that contains main() function — to 2.9. In Flutter apps, this file is often named lib/main.dart. In command-line apps, this file is often named bin/.dart. You can also opt out files under test, because they are also entrypoints.
https://dart.dev/null-safety/unsound-null-safety
From dart.dev, I used it when I was having problems with packages without null-safety.
Related
I have the following problem.....
Error: Variables must be declared using the keywords 'const', 'final', 'var' or a type name.
Try adding the name of the type of the variable or the keyword 'var'.
int _counter = 0;dsggfsgfh;
^^^^^^^^^
Target kernel_snapshot failed: Exception
FAILURE: Build failed with an exception.
I'm a beginner with Flutter. How can I solve this problem?
Your code has junk words or sentences, check your line ended with dsggfsgfh; which might be added unfortunately. Just remove it this will work.
It's possible that it's a compatibility issue between flutter framework and engine. You can try and:
Upgrade flutter to the latest version
Create a new project
Copy the code from the old project in steps
If you have plugins from the old project, add them one by one as you run the emulator
(It's possible that a certain version of a plugin has a compatibility issue with flutter)
I'm making a library for persistence implementation. For that I want to use reflection to be able to restore an object from the storage.
I can't use dart:mirrors because this library will be use also in Flutter application. So I'm trying to use reflectable package. And here I'm getting a major issue with understanding of how it should work. The doc tells reflectable uses build package and that some files must be generated. But I couldn't find anywhere whether this generation should happen for each file in my library package or just those where reflectable is used.
My library project structure is standard:
/examples
/lib
/lib/src
/lib/my_package.dart
/test
/pubspec.yaml
When I run dart run build_runner or dart run build_runner lib from the project root I see for each file in /example and /tests a matching file is generated. But in /lib folder nothing is generated. Only file where I'm intending to use reflectable is /lib/src/persistence/persistence_model.dart. I've created a file /lib/build.yaml of following content:
targets:
$default:
builders:
reflectable:
generate_for:
- src/persistence/persistence_model.dart
options:
formatted: true
but it seems to have no effect.
So, what should be right approach?
And probably a side question or rather consideration: isn't using reflection in Dart and Flutter excessively complex comparing to other languages (Python, C#, Java)?
I have been developing application and one of the libraries I have used was Flutter Redux Navigation. Everything was working fine, until recently, when I started getting following error
../../lib/src/navigation_middleware.dart:3:1: Error: 'NavigationDestination' is imported from both 'package:flutter/src/material/navigation_bar.dart' and 'package:flutter_redux_navigation/src/navigation_destination.dart'.
import 'package:flutter_redux_navigation/src/navigation_destination.dart';
^^^^^^^^^^^^^^^^^^^^^
../../lib/src/navigation_middleware.dart:35:26: Error: 'NavigationDestination' is imported from both 'package:flutter/src/material/navigation_bar.dart' and 'package:flutter_redux_navigation/src/navigation_destination.dart'.
this._setState(NavigationDestination(
^^^^^^^^^^^^^^^^^^^^^
../../lib/src/navigation_middleware.dart:55:26: Error: 'NavigationDestination' is imported from both 'package:flutter/src/material/navigation_bar.dart' and 'package:flutter_redux_navigation/src/navigation_destination.dart'.
this._setState(NavigationDestination(
I even tried to copy example project from their git, and got exactly same error. This is something in library, or perhaps some settings of my IDE? Please let me know if anyone encountered this error.
The problem was that I have upgraded Flutter version from 2.5.1 to 2.8.0. The newest Flutter version contains upgraded Material library, which contains the method called NavigationDestination. Thus both, the library and Material design have the same name of the class, of course, resulting in error.
I'm trying to add AppCenter to my application but I get build error:
Error: Cannot run with sound null safety, because the following
dependencies don't support null safety:
package:appcenter
package:appcenter_analytics
package:appcenter_crashes
For solutions, see https://dart.dev/go/unsound-null-safety
FAILURE: Build failed with an exception.
I added auto-generated code from AppCenter to my ->app/build.gradle
dependencies {
def appCenterSdkVersion = '4.3.1'
implementation "com.microsoft.appcenter:appcenter-analytics:${appCenterSdkVersion}"
implementation "com.microsoft.appcenter:appcenter-crashes:${appCenterSdkVersion}"
}
Spending some hours in pain, I found my solution and post it here
We should not import appcenter, appcenter_analytics appcenter_crashespackage in main.dart (also not import them into pubspec.yaml)
What we should do is, override "onCreate" method in MainActivity.java and implement appcenter there.
You can find more details in my answer.
I have 2 issues that only appear when executing flutter build web.
Sometimes flutter build web fails complaining (wrongly) about types that were not compatible (see below).
Sometimes the build process finishes but then the web app doesn't work: doesn't display anything and there are no messages in the console.
The error I mention is something like this:
% flutter build web
Target dart2js failed: Exception: lib/main.dart:24:31:
Error: A value of type 'ApiUsersRepository' can't be assigned to a variable of type 'UsersRepository'.
- 'ApiUsersRepository' is from 'package:my_app/api_users_repo.dart' ('lib/api_users_repo.dart').
- 'UsersRepository' is from 'lib/users_repo.dart'.
final UsersRepository usersRepository = ApiUsersRepository();
^
Error: Compilation failed.
The app is working in iOS and web when developing.
The solution
I changed all imports of my files like:
import 'package:my_app/users_repo.dart';
To:
import 'users_repo.dart';
More Details
Investigating the error about types, I found this issue, where the important part is this comment: after changing every import to relative format it resolves my problem.
So I did that, and it solved the 2 issues, the compilation error, and the runtime error.
for me I had to remove a package that was corrupted. c:\src\flutter.pub-cache\hosted\pub.dartlang.org\localstorage-4.0.0+1 Apparently, a file had become corrupted by me invertly. I removed the package and did a flutter pub get then recompiled and it worked.