MetroX Android

Core Android support for Metro. This artifact specifically focuses on integration with AppComponentFactory, which requires API 28+. As a result, this artifact requires min SDK 28 since it’s useless on older versions.

Usage

For simple cases, all you need to do is

1. Depend on this artifact

   
   

   dependencies {
     implementation("dev.zacsweers.metro:metrox-android:x.y.z")
   }
   

   
   2. Make your AppGraph (or equivalent) implement MetroAppComponentProviders.
   

   @DependencyGraph(AppScope::class)
   interface AppGraph : MetroAppComponentProviders
   

   
   3. Make your Application subclass implement MetroApplication and implement appComponentProviders.
   

   class MyApp : Application(), MetroApplication {
     private val appGraph by lazy { createGraph<AppGraph>() }
     override val appComponentProviders: MetroAppComponentProviders
       get() = appGraph
   }
   

Injecting Android app components

To constructor inject Android app components (Activity, Service, etc), annotate them with the corresponding map key and contribute them into the maps used by MetroAppComponentFactory.

For example, use @ActivityKey for an injected Activity:

@ContributesIntoMap(AppScope::class, binding<Activity>())
@ActivityKey(MainActivity::class)
class MainActivity(private val fragmentFactory: FragmentFactory): AppCompatActivity()

For other types of components, use @BroadcastReceiverKey, @ContentProviderKey, and @ServiceKey the same way.

Note that the built-in MetroAppComponentFactory uses the base Activity, Service, etc types. If you want to use your own bases (ComponentActivity, etc), you’ll need to create your own AppComponentFactory + relevant multibindings typed to the key you need.

Advanced

If you have your own custom AppComponentFactory, you will need to exclude the MetroX implementation in your AndroidManifest.xml via tools:replace attribute.

<?xml version="1.0" encoding="utf-8"?>
<manifest
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools">

  <application
    ...
    android:appComponentFactory="your.custom.AppComponentFactory"
    tools:replace="android:appComponentFactory"
  >
  </application>
</manifest>

Then you can replicate what MetroAppComponentFactory does or subclass it in your custom factory.