How to solved 'dart:ui' error when going to run flutter app?

Question

Below error occurs when I try to run my first flutter app.

file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/action_sheet.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show ImageFilter;
       ^
 file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/bottom_tab_bar.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show ImageFilter;
       ^
file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/colors.dart:5:8: Error: Not found: 'dart:ui'
import 'dart:ui' show Color;
       ^
file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/dialog.dart:6:8: Error: Not found: 'dart:ui'
import 'dart:ui' show ImageFilter;
       ^
 file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/nav_bar.dart:6:8: Error: Not found: 'dart:ui'
import 'dart:ui' show ImageFilter;
       ^
 file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/slider.dart:6:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
 file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/cupertino/switch.dart:6:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^
 file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/material/animated_icons.dart:9:8: Error: Not found: 'dart:ui'
import 'dart:ui' as ui show Paint, Path, Canvas;
       ^   file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/material/animated_icons.dart:10:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^  file:///Volumes/Data/FlutterSDk/flutter/packages/flutter/lib/src/material/arc.dart:6:8: Error: Not found: 'dart:ui'
import 'dart:ui' show lerpDouble;
       ^

Process finished with exit code 254

I have tried many ways to solve this issue but still, this issue is coming.

are you sure you installed dart plugin correctly? Can you share your `flutter doctor -v` result? — salihgueler, Jan 07 '19 at 10:28
yes because when I fire "flutter Doctor" its display no error. — Pratik Satani, Jan 07 '19 at 10:31
I mean all the errors works fine on my PC. Can you share your `flutter doctor -v` result? It doesn't have to show an error, seeing your system information is also useful.With the only code above, no one can help. — salihgueler, Jan 07 '19 at 10:40
When run the app, you will find 2 main.dart Choose the one with the flutter icon beside it enter image. Check this image https://i.stack.imgur.com/kAGBx.png — salihgueler, Jan 07 '19 at 10:54

score 38 · Answer 1 · edited Dec 21 '21 at 03:00

38

You are getting those errors because your IDE is executing main.dart as a simple dart application and not as a Flutter application.

As answered by salihguler, if you are using Android SDK then choose the main.dart file with Flutter Icon beside it and not the one with Dart Icon and the project should work just fine.

If you are using VS Code then instead of hitting Run (Ctrl+Alt+N) go to Debug -> Start Debugging option or simply press F5 and errors will be gone.

edited Dec 21 '21 at 03:00

Nimantha

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answered Nov 22 '19 at 19:56

Ketan Ramteke

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It solved my problem. Thanks. After trying funny solutions I came here and voila – Ishmael Mavor Raines Jan 01 '23 at 14:43

score 23 · Accepted Answer · edited Feb 01 '20 at 00:40

23

When you run the app, you will see 2 main.dart entry. Please pick the one with Flutter icon. I get it from here.

edited Feb 01 '20 at 00:40

Aleksandr Belugin

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answered Jan 07 '19 at 12:11

salihgueler

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score 2 · Answer 3 · answered Aug 19 '21 at 07:33

For me the culprit was a transitive dependency on Flutter. I was running a dart file that imported a functional class that I copied from another project. This class did not apparently depend on Flutter but it was importing a package for logging and that package was depending on Flutter.

When running a dart executable, make sure you do not use any Flutter specific classes anywhere.

score 0 · Answer 4 · answered Jun 08 '19 at 15:22

If you are using VSCode, you might need to open Folder more closely to your main.dart.

Bad Folder Structure Example on the left side:

Backend
Frontend
- FlutterApp
- lib
  - main.dart

Working:

FlutterApp
- lib
  - main.dart

Finally, I saved workplace as second one, and changed to first one, all works! Here is the related issue discussion.

score 0 · Answer 5 · answered Mar 23 '20 at 14:28

had the same error message when working on command line based dart files, i had accidentally

imported cupertino packages on some dart files. try using material design only on your project and remove the cupertino package import on your files P.S i had no issue working on the real flutter app. and i use android studio

score 0 · Answer 6 · answered Mar 28 '20 at 06:15

0

I was having the same problem, but pressing "F5 running on debug mode" worked for me. Additionally I don't need to install XCode and Android Studio as well, which was described as a problem in flutter doctor command.

answered Mar 28 '20 at 06:15

Jay Dangar

3,271
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score 0 · Answer 7 · edited Feb 20 '22 at 12:50

0

If you're on VS code and are using extensions to run the code, don't. You should disable them and use the flutter extension it self to launch the main.dart.

edited Feb 20 '22 at 12:50

ouflak

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answered Feb 20 '22 at 10:00

Metmiku Yohannes

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Ali Erdem Toraman · Answer 8 · 2022-08-26T03:23:58.330

0

dude this is a bit silly and ridiculous but are you sure you have the code void main(){} inside your main.dart file?

edited Aug 26 '22 at 03:23

answered Aug 26 '22 at 03:23

Ali Erdem Toraman

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I have asked before 7 months when I was new in a flutter. – Pratik Satani Aug 29 '22 at 11:23

How to solved 'dart:ui' error when going to run flutter app?

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