Flutter：找不到目标文件“lib/main.dart”

Question

When I perform a flutter run I get an error

Target file "lib/main.dart" not found.

Why is this happening and how can I fix this?

Answer 1

You can run any file from any DIR provided that you set the target file path, example:

flutter run -t lib/main_dev.dart

OR

flutter run lib/dev/main_dev.dart

UPDATE (2020 February 5th)

It is however not advisable to remove main.dart from your project.

I'm sure most of you found this link because you are setting up / configuring your app to accommodate for different environments eg dev, stg, beta and prod.

Example:

main_dev.dart:

void main() async {
  dynamic configuredApp = AppConfig(
    appName: 'Flutter',
    flavorName: 'development',
    appVersion: 1.0,
    apiBaseUrl: 'https://dev-api.example.com/'
  );

  runApp(App(configuredApp));
}

main.dart

class App extends StatefulWidget {
  final dynamic configuredApp;

  App(this.configuredApp);

  @override
  _AppState createState() => _AppState();
}

As it turns out some build steps will fail in Android Studio mostly Gradle related if you don't have a main.dart file and method main() {} referenced inside this file.

• Common build errors (AndroidX migrate, APK build etc.)

• More info / solutions below related to flutter build error: finished with non-zero exit value 1

  1. issuecomment
  2. issuecomment
  3. issuecomment

---

An alternative to flutter run -t lib/main_dev.dart in VS Code with the debugger tool.

• Click "Add Configuration" and add the following or add manually:

.vscode/launch.json

  "configurations": [

    {
      "name": "Flutter",
      "request": "launch",
      "type": "dart",
      // "args": ["--enable-software-rendering"]
      // "flutterMode": "profile", //debug //release 
      "program": "${workspaceFolder}/lib/main_dev.dart"
    }
  ]

Hope this helps.

Answer 2

Flutter is looking for main.dart in lib folder while you must have had file inside any other package.

Best solution is to place your main.dart file just inside lib folder. Flutter run command will work then for sure.

It worked for me.

main.dart url should be:

<app dir>/lib/main.dart

Answer 3

If you are using vscode...

When the error occurs, the vscode folder occurs in the side bar. It has the launch.json file inside.

You can change the "program": "..." property in the launch.json file to run the .dart file in the directory where you want.

Answer 4

This happened when I used Visual Studio Code. What I did to fix the problem was by editing the .vscode/launch.json file and change the value of "program" to the absolute path of my main.dart file (eg C://... ).

Answer 5

So basically when you execute this

 flutter run

Flutter tries to find main.dart in /lib directory.

So if you have a file that is present in some other child directory of /lib directory or has a different name like result_page.dart , you'd encounter this error. Now, a lot of answers had suggested to either rename your file to main.dart or move it directly under /lib directory.

But you can actually simply run any file by simply providing the target file's path from the current directory like this -

flutter run --target=lib/customization/result_screen.dart

So this would simply execute my result_screen.dart file present under some other child directory called customization .

You can also generate the APK file following the same logic and the command would look like this -

flutter build apk --target=lib/customization/result_screen.dart --target-platform=android-arm64

where --target-platform=android-arm64 is optional and is meant for 64-bit Android devices which helps in reducing APK size which otherwise would generate a fat APK including both 32-bit and 64-bit binaries. More info here

Answer 6

If you are using visual code and you encounter this problem while debugging, just go to launch.json, go to the location of where your flutter app is located, to the lib folder and then to the main.dart ,copy the path then add it to the text program in the launch.json as indicated on the photo below

launch.json "program" path

Answer 7

VSCode 用户：请导航到 launch.json 并将“Program”行替换为以下内容：

"Program":"${rootProject.buildDir}/${project.name}/lib/main.dart"

Answer 8

in android studio this wokrs for me

1. left click in main.dart
2. right click in profile main.dart

this executes an snapshot aplicaction to configure the root profile a run your app

Answer 9

If you are using the Debug Mode in vs code , ensure that the vs code working folder is your Flutter project main folder.

If you want to change the vs code working folder, you can use the File > Open Folder menu or Ctrl+O shortcut.

When I change the folder, It worked for me .

Answer 10

What my case was I forgot to write code for calling main....

void main()
{
  runApp......
}

And doing this worked

Answer 11

Try final FlutterDevice flutterDevice = await FlutterDevice.create

The root cause is that the ResidentRunner we use to attach and do hot reloads will try to find a main.dart file when a target isn't announced. Attach doesn't provide a target, so it uses the default behavior always. As per DaceShuckerow .

This issue is still there on the official Repo .

Answer 12

If you are using VSCODE

Check folder .vscode>launch.json and add configuration:
if you have it already change a "program": "path of main.dart example: lib/main.dart"

 { "name": "Dart", "type": "dart", "request": "launch", "program": "lib/main.dart" },

Answer 13

If you are using VSCode then try this method :
Delete .vscode folder in your project directory and rerun the program.

Answer 14

If you are having multiple iOS schemes then you could try like this:

flutter run --flavor UserDev -t lib/user/dev/main_dev.dart

For,

"configurations": [{
            "name": "User-Dev",
            "request": "launch",
            "type": "dart",
            "program": "lib/user/dev/main_dev.dart",
            "args": [
                "--flavor",
                "UserDev"
            ]
        }]

Answer 15

In case someone is struggling with this what worked for me is to recreate ios folder. And -t works regardless of the location of the target or name of the target and without any need to have main.dart in your lib folder.

To recreate ios folder

• rename ios folder to something like ios_old
• run => flutter create fakeApp
• open fakeApp, copy the ios folder to your project
• migrate changes from ios_old (if you had any changes)
• delete ios_old

Answer 16

我有一个类似的错误信息，这是因为我不小心删除了 void main()

Answer 17

Make Sure that your main.dart inside lib folder directly not in another package or directory

Answer 18

I think you already change the path of main.dart.If so You can drag and drop the main.dart file to lib folder.(lib/main.dart)