Registering an parent class does not work

[mr-thierry]

I have a parent activity that contains a @Subscribe method. When I try to register the parent using bus.register(this), the AnnotatedHandlerFinder finds all @Subscribe methods in the child class, not in the parent.

That's because:
AnnotatedHandlerFinder.findAllSubscribers() take the class of the instance and not the parent.

A solution would be to add a new method bus.register(this, listenerClass), where listenerClassis the type of the parent object?

[JakeWharton]

This is by design to ensure fast performance on Android and is documented behavior on the website. Version 2.0 will use code-gen to restore entire class hierarchy subscription but all of the Version 1.x releases will only look at the concrete class type for annotations.

[mr-thierry]

I understood that registering will not "walk up" the hierachy to automatically register the parent classes. But the issue is that any registration call in a parent will never work with Otto v1. Even if the parent is not an abstract class.

You might want to clarify this point in the docs. :)

Or release v2 soon. ;)

[JakeWharton]

I'm not sure what you mean that registration in a parent will not work. We have base fragments and activities which do registration on behalf of their extending classes which works. When you call this from a base activity you are still referring to the extending type and not the type of the class in which the call is made.

[mr-thierry]

Let me rephrase my problem: any @Subscribe method in a parent is never registered. Take the following code:

public class ParentActivity extends Activity {

    @Subscribe
    public void onReceiveLoginEvent(final LoginEvent event) {
        Log.d("Tag", "LoginEvent");
    }

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        BusProvider.getInstance().register(this);
    }
}


public class ChildActivity extends ParentClass {

    @Subscribe
    public void onReceiveErrorEvent(final ErrorEvent event) {

    }

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        BusProvider.getInstance().register(this);

        setContentView(R.layout.main);

        BusProvider.getInstance().post(new LoginEvent());
    }

}

When ParentActivity register to the bus, the AnnotatedHandlerFinder picks up the @Subscribe onReceiveErrorEvent method from ChildActivity. I cannot find a way to register the ParentActivity @Subscribe onReceiveLoginEvent method.

public class ParentActivity extends Activity {

@Subscribe
public void onReceiveLoginEvent(final LoginEvent event) {
    Log.d("Tag", "LoginEvent");
}

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BusProvider.getInstance().register(new Object() {
      @Subscribe
      public void onReceiveLoginEvent(final LoginEvent event) {
        Log.d("Tag", "LoginEvent");
      }
    });
}

}

On Thu, Oct 11, 2012 at 9:33 AM, thierryd notifications@github.com wrote:

Let me rephrase my problem: any @subscribe method in a parent is never
registered. Take the following code:

public class ParentActivity extends Activity {

@Subscribe
public void onReceiveLoginEvent(final LoginEvent event) {
    Log.d("Tag", "LoginEvent");
}

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BusProvider.getInstance().register(this);
}

}

public class ChildActivity extends ParentClass {

@Subscribe
public void onReceiveErrorEvent(final ErrorEvent event) {

}

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BusProvider.getInstance().register(this);

    setContentView(R.layout.main);

    BusProvider.getInstance().post(new LoginEvent());
}

}

When ParentActivity register to the bus, the AnnotatedHandlerFinder picks
up the @subscribe onReceiveErrorEvent method from ChildActivity. I cannot
find a way to register the ParentActivity @subscribe onReceiveLoginEventmethod.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/26#issuecomment-9347469.

Should delete the old instance method, of course. Fixed in the quoted text
below.

On Thu, Oct 11, 2012 at 9:35 AM, Ray Ryan ray@squareup.com wrote:

public class ParentActivity extends Activity {

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BusProvider.getInstance().register(new Object() {
      @Subscribe
      public void onReceiveLoginEvent(final LoginEvent event) {
        Log.d("Tag", "LoginEvent");
      }
    });
}

}

On Thu, Oct 11, 2012 at 9:33 AM, thierryd notifications@github.comwrote:

Let me rephrase my problem: any @subscribe method in a parent is never
registered. Take the following code:

public class ParentActivity extends Activity {

@Subscribe
public void onReceiveLoginEvent(final LoginEvent event) {
    Log.d("Tag", "LoginEvent");
}

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BusProvider.getInstance().register(this);
}

}

public class ChildActivity extends ParentClass {

@Subscribe
public void onReceiveErrorEvent(final ErrorEvent event) {

}

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BusProvider.getInstance().register(this);

    setContentView(R.layout.main);

    BusProvider.getInstance().post(new LoginEvent());
}

}

When ParentActivity register to the bus, the AnnotatedHandlerFinderpicks up the @subscribe
onReceiveErrorEvent method from ChildActivity. I cannot find a way to
register the ParentActivity @subscribe onReceiveLoginEvent method.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/26#issuecomment-9347469.

[JakeWharton]

Yes. That is because in both registrations this always refers to an object of type ChildActivity even if in the IDE reports this as being of type ParentActivity in the former call. This is not a limitation of the library (beyond the documented omission of class hierarchy traversal) but it is just how Java works.

[mr-thierry]

@RayFromSquare Thanks for the tip. That's a nice way to work around the limitation. :)

[mr-thierry]

After some consideration @RayFromSquare solution is not perfect. The best way would be to create an anonymous inner class and assign a variable to it so that it can be unregistered later. :)

[felipecsl]

So just to illustrate @ThierryD comment:

public class ParentActivity extends Activity {
    private Object busEventListener;

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

         busEventListener = new Object() {
            @Subscribe
            public void onReceiveLoginEvent(final LoginEvent event) {
                Log.d("Tag", "LoginEvent");
            }
        };

        BusProvider.getInstance().register(busEventListener);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        BusProvider.getInstance().unregister(busEventListener);
    }
}

[gmale]

Thanks so much @felipecsl, @ThierryD and @RayFromSquare for this approach. It makes perfect sense and solves the problem, nicely. In case it helps anyone else, I had to tweak the implementation slightly to make it easier for subclasses to extend the behavior. Note: the listener can handle multiple events:

public class ParentActivity extends Activity {
    protected Object busEventListener;

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

         busEventListener = new Object() {
            @Subscribe
            public void onReceiveLoginEvent(final LoginEvent event) {
                ParentActivity.this.onReceiveLoginEvent(event);
            }
            @Subscribe
            public void onReceiveLogoutEvent(final LogoutEvent event) {
                ParentActivity.this.onReceiveLogoutEvent(event);
            }
        };

        BusProvider.getInstance().register(busEventListener);
    }

    //subclasses extend me. This can be abstract, if necessary.
    protected void onReceiveLoginEvent(final LoginEvent event) {
        Log.d("Tag", "LoginEvent");
    }

    //subclasses extend me. This can be abstract, if necessary.
    protected void onReceiveLogoutEvent(final LogoutEvent event) {
        Log.d("Tag", "LogoutEvent");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        BusProvider.getInstance().unregister(busEventListener);
    }
}

This is tested and working. The parent class takes care of the boilerplate work and subclasses add a bit more functionality, when needed. Perfect. Thanks again!

[gautamk]

When using the method @gmale suggested make sure the overriding methods in the child class are not annotated with @Subscribe

[xxdondi]

Although there is a shortcoming to @gmale 's approach: the parent class must contain every possible event handler that it's ancestors might have, because otherwise they would have nothing to override and if they use @Subscribe, they simply won't get notified of any events because their instances are not registered in the bus, only the listener object is.
I hope #135 will be merged soon.