Flutter / Dart syntax highlighting is not working - flutter

Question

The syntax of the dartcode in my flutter project is no longer being highlighted and cannot click the declarations or do autocomplete of code, like typing: StreamBuilder( and then click enter to create the widget for a streambuilder.
See example code below, where normaly, the different elements would be coloured:
This problem occured after I installed intelliJ, I did this because I needed to write some javascript for firebase functions.
Tried this so far, with no luck:
deleting android studio and re-install it.
invalidate caches and restart.
restart analyses server
checked that dart and flutter has the right paths under 'languages & frameworks'
created a new flutter project, here everything works just fine. but if i copy in my codebase the issue persists
Im using android studios latest version.
EDIT:
Apparently I have some issues after all with the plugins. But as seen in the picture, I've given the paths to both flutter and dart.
Its somehow related to intelliJ because when i click the links from the flutter doctor output it takes me to jetbrains website
[✓] Flutter (Channel stable, 2.2.3, on macOS 11.3 20E232 darwin-x64, locale da-DK)
• Flutter version 2.2.3 at /Users/jeffmayn/Desktop/Development/flutter
• Framework revision f4abaa0735 (10 weeks ago), 2021-07-01 12:46:11 -0700
• Engine revision 241c87ad80
• Dart version 2.13.4
[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
• Android SDK at /Users/jeffmayn/Library/Android/sdk
• Platform android-30, build-tools 30.0.3
• Java binary at: /Library/Java/JavaVirtualMachines/jdk-15.0.1.jdk/Contents/Home/bin/java
• Java version Java(TM) SE Runtime Environment (build 15.0.1+9-18)
✗ Android license status unknown.
Run `flutter doctor --android-licenses` to accept the SDK licenses.
See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.
[✓] Xcode - develop for iOS and macOS
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 12.5.1, Build version 12E507
• CocoaPods version 1.10.1
[✓] Chrome - develop for the web
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
[!] Android Studio (version 2020.3)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
🔨 https://plugins.jetbrains.com/plugin/6351-dart
✗ Unable to find bundled Java version.
• Try updating or re-installing Android Studio.
[✓] Connected device (2 available)
• Android SDK built for x86 (mobile) • emulator-5554 • android-x86 • Android 10 (API 29) (emulator)
• Chrome (web) • chrome • web-javascript • Google Chrome 93.0.4577.63
! Doctor found issues in 2 categories.
Process finished with exit code 0

Answer 1

I think reinstalling Flutter and Dart plugin to Android Studio can help. Syntax highlighting is plugins' job.

Answer 2

The solution of yoppuyoppu worked for me, but as he mentioned, only for the selected files.
So here is a small addition that makes it work for all .dart files:
In the "Register New File Type Association" window you can change the File pattern to "*.dart".
And of course select Dart as shown.
That way all files ending with ".dart" will be associated with Dart.

Answer 3

In my case, only one file had such problem. And it turned out I screwed up the file type association of the file when I created it.
Fix was to reassociate the file with Dart.
Go to the menu bar >> File >> File Properties >> Associate with File Type...
And in the dialog that follows, pick Dart and click OK.
You can choose as many files as you like at any one time.

Answer 4

None of the suggested solutions worked out for me. What I did was then:
create a new flutter project.
setup dart and flutter plugins.
copy in all my code, files, assets, etc. from the old project to the new.