Dagger2 Component (un-scoped) cannot depend on scoped components - Error

Question

I am trying to compile https://github.com/svenjacobs/android-dagger2-example but I am running into an error related to unscoped component depending on scoped components. (Android Studio 1.1, Gradle 2.2.1). Also if anyone knows of other Dagger2 Android examples WITH FRAGMENTS I would like to know about them.

UPDATE: Here is another example one very basic with fragments: https://github.com/gk5885/dagger-android-sample

/Users/Mac1/android-dagger2-example-master/app/src/main/java/com/svenjacobs/dagger2/ActivityComponent.java
Error:(15, 1) error: com.svenjacobs.dagger2.ActivityComponent (unscoped) cannot depend on scoped components:
@Singleton com.svenjacobs.dagger2.ApplicationComponent
Error:Execution failed for task ':app:compileDebugJava'.
> Compilation failed; see the compiler error output for details.

Here is the file ActivityComponent which is apparently not scoped:

import dagger.Component;

/**
 * Component for all activities.
 *
 * @author Sven Jacobs
 */
@Component(dependencies = ApplicationComponent.class,
       modules = {
               MainActivityModule.class,
               AModule.class,
               BModule.class
       })
interface ActivityComponent extends AFragment.Injector, BFragment.Injector  {

    void inject(MainActivity activity);

    void inject(AnotherActivity activity);
}

And here is the scoped component:

package com.svenjacobs.dagger2;

import javax.inject.Singleton;

import dagger.Component;

/**
 * Application-wide dependencies.
 *
 * @author Sven Jacobs
 */
@Singleton
@Component(modules = ApplicationModule.class)
interface ApplicationComponent {

void inject(Dagger2Application application);

/**
 * Provides dependency for sub-components
 */
SomeApplicationDependency someApplicationDependency();
  }

Answer 1

You need to provide a scope for the ApplicationComponent. This doesn't necessarily have to be @Singleton, since Dagger 2 allows you to define your own scopes using the @Qualifier annotation on an interface.

@Scope
public @interface CustomScopeName {
}

You could then use it like so:

@CustomScopeName
@Component(dependencies = ApplicationComponent.class,
   modules = {
           MainActivityModule.class,
           AModule.class,
           BModule.class
   }) .......

I think the reason you aren't allowed to use a scoped dependency in an unscoped component is to prevent Singletons from depending on non-Singleton objects and prevent cyclic dependencies.