public abstract class WViewWidget extends WWebWidget
In principle, JWt widgets are self-contained and manage both their content, behavior and
layout. From the point of view of a Model-View-Controller (MVC) design pattern, they implement
each of these, except for the view widgets that work in conjunction with
WAbstractItemModel. As a developer you can chose to keep Model, View and Controller together or
separate them as you wish.
This widget facilitates separation of the View from the Model and Controller in a particular way. The View is rendered as a JWt widget. The use of this widget provides two benefits. The classic MVC benefit is a decoupling between view and model, which may allow easier maintainance of code. In addition, this widget enforces the View to be stateless, as it is only created transiently on the server. Therefore the View does not require session resources. This may increase scalability for Internet-deployments.
Currently, the View cannot enclose
WFormWidgets which would allow direct
manipulation of the model (but we are working to remove this limitation in the future, and let
the Model/Controller handle editing changes) and the View may only be updated by a complete
rerendering of the entire view.
The View widget may contain event handling code, but only in one of the following ways:
- event handling implemented in pre-learned stateless slot implementations
This widget does not provide styling, and can be styled using inline or external CSS as appropriate.
Nested Class Summary
Constructors Constructor Description
()Creates a new view widget.
WContainerWidget parent)(Creates a new view widget.
Methods inherited from class eu.webtoolkit.jwt.WWebWidget
Methods inherited from class eu.webtoolkit.jwt.WWidget
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
updatepublic void update()Updates the view.
Typically, the model will want to update the view when the model has changed.
This will trigger a call to
getRenderView()to ask for a new rendering of the view.
loadpublic void load()Loads content just before the widget is used.
This method is called after a widget is inserted in the widget hierarchy and fully constructed, but before the widget is rendered. Widgets that get inserted in the widget hierarchy will be rendered. Visible widgets are rendered immediately, and invisible widgets in the back-ground (or not for a plain HTML session). This method is called when the widget is directly or indirectly inserted into the widget tree.
The default implementation simply propagates the load signal to its children. You may want to override this method to delay loading of resource-intensive contents.
During the life-time of a widget, this method may be called multiple times, so you should make sure that you do a deferred initializiation only once.
renderpublic void render(java.util.EnumSet<RenderFlag> flags)Renders the widget.
This function renders the widget (or an update for the widget), after this has been scheduled using
refreshpublic void refresh()Refresh the widget.
The refresh method is invoked when the locale is changed using
WApplication#setLocale()or when the user hit the refresh button.
The widget must actualize its contents in response.
getRenderViewprotected abstract WWidget getRenderView()Creates a widget that renders the View.
This method must be reimplemented to return a widget that renders the view. The returned widget will be deleted by WViewWidget.