Using Android injector with SDK-level-dependent components.

I have a subclass of TileService (an android.app.Service that is only available on 24+). I want to use the Android injector and @ContributesAndroidInjector abstract MyTileService service(). This creates a service key of MyTileService.class in the generated module, ultimately resulting in the following as a field in my component.

this.mapOfClassOfAndProviderOfFactoryOfProvider =
        MapProviderFactory
            .<Class<? extends Service>, AndroidInjector.Factory<? extends Service>>builder(1)
            .put(MyTileService.class, bindAndroidInjectorFactoryProvider1)
            .build();

On Android versions <24, the reference to the class file tries to load the Android framework class (TileService) that doesn’t exist, crashing with a NoClassDefFoundError.

Can Dagger-Android do any clever lazy tricks to avoid this?

[tasomaniac]

For those who came across this issue. The solution was introduced in above commit.

You need to put the following argument to enable it. This will use Strings instead of Class references (which then fixes the mentioned crash). -Adagger.android.experimentalUseStringKeys

On Android java-only projects, you do

android {
    defaultConfig {
        javaCompileOptions.annotationProcessorOptions {
            arguments['dagger.android.experimentalUseStringKeys'] = 'true'
        }
    }
}

For Kotlin projects with kapt you would do

kapt {
  arguments {
    arg('dagger.android.experimentalUseStringKeys')
  }
}

Note: More explanation on how this works and its effects on Proguard/R8 is available here: https://github.com/google/dagger/blob/3a089646fb70fb5a193a731c4909d6ccaeeaadd3/java/dagger/android/processor/AndroidProcessor.java#L44-L52

Note 2: Keep in mind that enabling this also breaks incremental annotation processor support on Dagger 5.+

[markuspfeiffer]

I’ve just run into the same issue using a subclass of JobService. Naturally the service is only used on devices running Android 5.x or newer.

As a possible way to add support for this in Dagger, how about using the @RequiresApi annotation?

@ContributesAndroidInjector
@RequiresApi(VERSION_CODES.LOLLIPOP)
JobService jobService();

If this annotation is present, the generated code could be modified to look like this:

private Map<Class<? extends Service>, Provider<AndroidInjector.Factory<? extends Service>>> getMapOfClassOfAndProviderOfFactoryOf3() {

  MapBuilder mapBuilder = MapBuilder.<Class<? extends Service>, Provider<AndroidInjector.Factory<? extends Service>>>newMapBuilder(3)
      .put(FooService.class, (Provider) fooServiceSubcomponentBuilderProvider)
      .put(BarService.class, (Provider) barServiceSubcomponentBuilderProvider);

  if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
      mapBuilder.put(JobService.class, (Provider) jobServiceSubcomponentBuilderProvider)
  }

  return mapBuilder.build();
}

~edit: Updated as per Jake Wharton’s comment. Thanks for the correction.