Navigating in an Application

The Navigator class manages a collection of views that implement the View interface. The views can be either registered beforehand or acquired from a view provider. When registering, the views must have a name identifier and be added to a navigator with addView(). You can register new views at any point. Once registered, you can navigate to them with navigateTo().

Navigator manages navigation in a component container, which can be either a ComponentContainer (most layouts) or a SingleComponentContainer ( UI, Panel, or Window). The component container is managed through a ViewDisplay. Two view displays are defined: ComponentContainerViewDisplay and SingleComponentContainerViewDisplay, for the respective component container types. Normally, you can let the navigator create the view display internally, as we do in the example below, but you can also create it yourself to customize it.

Let us consider the following UI with two views: start and main. Here, we define their names with enums to be typesafe. We manage the navigation with the UI class itself, which is a SingleComponentContainer.

Java

See the on-line example.

The Navigator automatically sets the URI fragment of the application URL. It also registers a URIFragmentChangedListener in the page

(see ) to show the view identified by the URI fragment if entered or navigated to in the browser. This also enables browser navigation history in the application.

You can create new views dynamically using a view provider that implements the ViewProvider interface. A provider is registered in Navigator with addProvider().

The ClassBasedViewProvider is a view provider that can dynamically create new instances of a specified view class based on the view name.

View Change Listeners

You can handle view changes also by implementing a ViewChangeListener and adding it to a Navigator. When a view change occurs, a listener receives a ViewChangeEvent object, which has references to the old and the activated view, the name of the activated view, as well as the fragment parameters.

Views can be any objects that implement the View interface. When the navigateTo() is called for the navigator, or the application is opened with the URI fragment associated with the view, the navigator switches to the view and calls its enter() method.

To continue with the example, consider the following simple start view that just lets the user to navigate to the main view. It only pops up a notification when the user navigates to it and displays the navigation button.

Java

See the .

You can initialize the view content in the constructor, as was done in the example above, or in the enter() method. The advantage with the latter method is that the view is attached to the view container as well as to the UI at that time, which is not the case in the constructor.

URI fragment part of a URL is the part after a hash # character. Is used for within-UI URLs, because it is the only part of the URL that can be changed with JavaScript from within a page without reloading the page. The URLs with URI fragments can be used for hyperlinking and bookmarking, as well as browser history, just like any other URLs. In addition, an exclamation mark #! after the hash marks that the page is a stateful AJAX page, which can be crawled by search engines. Crawling requires that the application also responds to special URLs to get the searchable content. URI fragments are managed by Page, which provides a low-level API.

URI fragments can be used with Navigator in two ways: for navigating to a view and to a state within a view. The URI fragment accepted by navigateTo() can have the view name at the root, followed by fragment parameters after a slash (“ /“). These parameters are passed to the enter() method in the View.

In the following example, we implement within-view navigation. Here we use the following declarative design for the view:

The view’s logic code would be as follows:

Java

See the on-line example.

The animal sub-view would have the following declarative design:

HTML

See the .

The main view is shown in Navigator Main View. At this point, the URL would be .

Navigator Main View