How to use --dart-define in a Flutter app embdedded in Android

Question

I'm Embedding a Flutter app as a module within an existing Android app ( https://flutter.dev/docs/development/add-to-app/android/project-setup ) and would like to know if/how I can use "--dart-define" to define compile-time constants. Tried using ./gradlew -Ddart-define=myVal=Value without any luck.

When building a typical Flutter app I would use the flutter command. In my case I'm continuing to use gradlew to build my app and it's unclear how to pass in --dart-define constants.

Answer 1

If your project depends on the Android Archive (AAR).

You can pass the dart-defines in the command line.

flutter build aar --dart-define=myVal=Value

If your project depends on the module's source code.

You can set dart-define s in gradle.properties in your android host project directory （or in yourHostProject/yourFlutter/.android/Flutter/ directory）.

--dart-define=myVal=Value 

Explanation

• .android/Flutter/build.gradle script executes "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle" script. When the flutter.gradle is executed, your dart files are compiled into naitive code.

• flutter.gradle loads dart-defines from the .android/Flutter project instance （ flutter.gradle#731-L734 ) and then, use it ( flutter.gradle#L1091-L1093 ).

• To set the project instance value, you add --dart-define=myVal=Value into gradle.properties . (If you have multiple gradle.properties files, consider configuration order（ Gradle properties in Gradle Docs ).

Answer 2

In android studio you may edit running configuration (press drop-down near "run" button -> "Edit configurations...") and define variables there ("Additional run args:" row):

--dart-define="http_serv=http://10.0.2.2:42627/" --dart-define="websocket=ws://10.0.2.2:42627/websocket"

Getting variable in code:

final checkArgs = String.fromEnvironment('http_serv', defaultValue: '');