dagger.android for views in ~10 minutes

dagger-android-view.md

1. You can implement View.getActivity() like this:

public interface ViewWithActivity {
  // Using android-gradle-plugin 3.0, which has the desugar step for default methods on interfaces
  default Activity getActivity() {
    // https://android.googlesource.com/platform/frameworks/support/+/03e0f3daf3c97ee95cd78b2f07bc9c1be05d43db/v7/mediarouter/src/android/support/v7/app/MediaRouteButton.java#276
    Context context = getContext();
    while (context instanceof ContextWrapper) {
      if (context instanceof Activity) {
        return (Activity)context;
      }
      context = ((ContextWrapper) context).getBaseContext();
    }
    throw new IllegalStateException("Context does not stem from an activity: " + getContext());
  }
}

2. Create a parallel to the Has*Injector classes

interface HasViewInjector {
  AndroidInjector<View> viewInjector();
}

3. Define a new activity base class:

public abstract DaggerAppCompatWithViewActivityNamingIsFun
    extends DaggerAppCompatActivity
    implements HasViewInjector {
  @Inject DispatchingAndroidInjector<View> viewInjector;
  
  @Override
  public AndroidInjector<View> viewInjector() {
    return viewInjector;
  }
}

4. Create a module

@Module
interface ViewInjectionModule {
  @Multibinds
  abstract Map<Class<? extends View>, AndroidInjector.Factory<? extends View>>
      viewInjectorFactories();
}

// ...

@Component(
  modules = {
    AndroidSupportInjectionModule.class,
    ViewInjectionModule.class, 
    // ...
  })
interface AppComponent

5. ViewInjection.inject

public final class ViewInjection {
  public static void inject(ViewWithActivity view) {
   checkNotNull(view, "view");
    Activity activity = view.getActivity();
    if (!(application instanceof HasViewInjector)) {
      throw new RuntimeException(
          String.format(
              "%s does not implement %s",
              activity.getClass().getCanonicalName(),
              HasViewInjector.class.getCanonicalName()));
    }

    AndroidInjector<View> viewInjector =
        ((HasViewInjector) activity).viewInjector();
    checkNotNull(viewInjector, "%s.viewInjector() returned null", activity.getClass());

    viewInjector.inject(view);
  }
}

6. Equivalent of @ContributesAndroidInjector MyView

7. Call ViewInjection.inject(this)

I'm not sure where this should happen yet, perhaps onFinishInflate or onAttachedToWindow()?