Custom inject

@CustomInject

In special circumstances, you may find that Hilt’s default behavior of injecting the Application class in super.onCreate is not suitable for your application. For example, there may be things that you want to do before injecting fields. In this case, you can use @CustomInject to control if/when the application is injected.

When you annotate your @HiltAndroidApp application class with @CustomInject, the injection no longer happens in onCreate. You can then use CustomInjection to inject your application at a time of your choosing.

Note: If you are not using the Gradle plugin and extend the generated Hilt base class directly, you can also just call the customInject() method which is on the generated base class.

Be aware that injection only injects the fields of the application and so is not required or necessary if there are no @Inject fields in your application or its base classes. Also note that this does not prevent the SingletonComponent from being instantiated. If other code requests the SingletonComponent like an @AndroidEntryPoint class being created, the SingletonComponent will still be created on demand.

Example

@CustomInject
@HiltAndroidApp
public final class MyApplication extends Application {
  @Inject Foo foo;

  @Override
  public void onCreate() {
    // Injection would normally happen in this super.onCreate() call, but won't
    // now because this is using CustomInject.
    super.onCreate();
    doSomethingBeforeInjection();
    // This call now injects the fields in the Application, like the foo field above.
    CustomInjection.inject(this);
  }
}

@CustomInject
@HiltAndroidApp
class MyApplication : Application() {
  @Inject lateinit var foo: Foo

  override fun onCreate() {
    // Injection would normally happen in this super.onCreate() call, but won't
    // now because this is using CustomInject.
    super.onCreate()
    doSomethingBeforeInjection()
    // This call now injects the fields in the Application, like the foo field above.
    CustomInjection.inject(this)
  }
}