Flutter app execution problems

[lucisays]

Good morning.

This morning I've been setting up everything to download projects from other years so I can see them visually and see which screens they have in common, that way getting an idea of what the basic screens should be. However, I keep getting this error when I use flutter run:

The full error would be:
C:\Program Files\Microsoft Visual Studio\2022\Community\MSBuild\Microsoft\VC\v170\Microsoft.CppCommon.targets(254,5): error MSB8066: Compilaci�n personalizada de "C:\Users\lucia\OneDrive\Escritorio\GSOC 2025\Proyectos usados\LG-Ship-Automatic-Identification-System-visualization\build\windows\x64\CMakeFiles\66f30bbb3f360a0c871a6033c1850cd4\flutter_windows.dll.rule;C:\Users\lucia\OneDrive\Escritorio\GSOC 2025\Proyectos usados\LG-Ship-Automatic-Identification-System-visualization\build\windows\x64\CMakeFiles\21a1707469fa6bb6f5614b4e904613db\flutter_assemble.rule;C:\Users\lucia\OneDrive\Escritorio\GSOC 2025\Proyectos usados\LG-Ship-Automatic-Identification-System-visualization\windows\flutter\CMakeLists.txt" terminada con el c�digo 1. [C:\Users\lucia\OneDrive\Escritorio\GSOC 2025\Proyectos usados\LG-Ship-Automatic-Identification-System-visualization\build\windows\x64\flutter\flutter_assemble.vcxproj]

The command flutter doctor gave me no errors, so I don't know what may be causing the problem. How can I solve this so I can execute the app?

Thanks!

[ClaudiaMihaelaDiosan]

@lucisays This error usually means that your app (or one of its dependencies) is trying to load an asset called env, but that file is either missing or not properly declared in your pubspec.yaml file.

Look for something like this:
rootBundle.loadString('assets/env');

Or
AssetImage('assets/env');

This means your app is trying to load a file called env, possibly something like env.json, .env, or another config file.

If the file exists:

Make sure it’s declared in your pubspec.yaml under the assets section. For example:
assets:
- assets/env.json

Then run:
flutter pub get

If the file does NOT exist

You have two options:
• Remove or comment out the code that tries to load the file, if it’s not necessary.
• Create the file, if you know what it’s supposed to contain (e.g., API keys, app settings, etc.).

The .env file is used usually for enviaronment variables that are used on the code and it uses to be created on the main root of the project.

[lucisays]

I've looked for the .env file and it does not exist. I tried to remove the line that tries to load the file, but it also gives an error. I thought about creating the .env file, but I don't really understand what it should have, nor I understand why it is not in the project if the code calls for it. What should I do to run the project?

[ClaudiaMihaelaDiosan]

@lucisays

In Flutter (and many other frameworks), .env files are often used to store environment variables — things like API keys, URLs, or secret settings that the app needs to run.

Usually, these files are not committed to the repository (they’re in .gitignore) because they can contain sensitive information.

So if the project you’re trying on is missing that .env file, it means:
• It was probably created by the original developer,
• But was not shared or included in version control,
• And the code depends on it to run.

Here are your options to get the app working:

1. Ask the project creator if you can

The best option: ask the student who created the project if he can give you a sample or development version of the .env file. I think he is on discord channel.

2. Check the code to see what values it needs

You can also try to find the code where the .env values are used. You might see somethinglike:

String apiKey = dotenv.env['API_KEY']!;

That tells you the file should contain something like:

API_KEY=your_api_key_here

You could create your own .env file in the root of the project and add placeholder values to test.

Example .env:

API_KEY=test_key
BASE_URL=https://example.com

3. Temporarily comment out or mock the values

If you only want to test the UI or local parts of the app, you might be able to comment out the parts of the code that use .env, and replace them with test values.

Example:

// String apiKey = dotenv.env['API_KEY']!;
String apiKey = 'test_key';

Just keep in mind that this only works if the .env values aren’t required by essential parts of the app (like database or backend calls).

Finally,

You mentioned you removed the line that loads the .env file, and it gave another error — that probably happened because the rest of the code still tries to use the variables from the .env, which now don’t exist, causing null or runtime errors.