I've downloaded Android source codes and find such things as `Context.java` lying in the `frameworks/base` directory. Thus, I can look around and know how an Android method is implemented. However, if I want to look at the life cycle of `Service` or `Bound Service`, which directory should I turn to? To be more specific, we know `onBind` method will return an `IBinder` object so I wonder where the object goes or who it is assigned to?