Fundamentals

H5Service, H5Session and H5Page are all extended from H5CoreNode class. With H5Service as the root node, they together forms a tree structure to represent the page flow and navigation. In normal circumstance, H5Pages are the leaf nodes to H5Session, whereas H5Sessions are the leaf nodes to H5Service, there is only one H5Service in any case.

H5Service

H5Service is the base class for maintaining global state of H5 application. There is only one singleton global instance of H5Service in the life cycle of H5 application, followings are some operations that you can use H5Service to perform

• Create and open a new web activity
• Create and start a new web page
• Store and retrieve shared data
• Register plugins and providers
• Listen to the life cycle of the application

H5Session

A H5Session is a stack of H5Pages that forms a complete business flow. e.g., A process of checkout could involves a few pages: A summary page to review the shopping cart, a payment method selection page to choose the desired payment method, and finally a payment page to fill in the payment info and confirm. All these pages can behave independently, and the role of H5Session here is to put these pages together, manage the sequence, handle the dependencies and achieve the business goal.

When you use H5Service to create and start a new web page, a new H5Session will be instantiated if there is none, and the subsequently created new pages will be added to this H5Session. You can also remove pages from the H5Session until the page stack is empty. H5Session also provides convenient methods for you to retrieve the top page or register a listener to listen to the life cycle events of H5Session.

H5Page

H5Page is the tangible component that user can actually see and interact with, and it is one of the most important part of an application’s overall life cycle. You can load the content by specifying a URL, customize the appearance and behavior of H5Page through a list of H5Param, and since you have the full access of its view hierarchy, it is also possible to put the H5Page together with other native UI components in the same layout.

Event

Nebula provides a event mechanism the allow event to be propagated among H5Page, H5Session and H5Service. A H5Event can occurs in H5Page, H5Session or H5Service, and there are two process in the event dispatch.

• Event interception, the event propagation goes from H5Service -> H5Session or H5Page, event can be intercepted ( if interceptEvent() returns true ) at any node during this propagation
• Event handling, the event propagation goes from H5Page -> H5Session or H5Service, event can be handled ( if handleEvent() returns true ) at any node during this propagation

If the event is intercepted or handled during interception or handling, the event is considered consumed and will not be propagated further, if a event is not consumed in both interception or handling after the dispatch, a error signal will be emitted to the caller.