Use views, not windows in Vaadin
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Join For FreeThis has lead some developers (including me) to think main windows
could be set and then removed later on: this is not the case and may
lead to nasty bugs when the page is refreshed by the user just after
having switched main windows.
Note: Vaadin 7 tackles the problem by merging the application and the main window into a single class (more in a later article).
In essence, when one has to fundamentally change what is shown to the user, one should use a custom component I call view. A view is just a group of components that are laid out together. Then, when we need to switch windows, we keep the main window and switch its content from one view to another: the main window becomes a just a placeholder. As an added value, since the main window is kept, it has always access to the parent application.
The application becomes something like this:
public class MyApplication extends Application { @Override public void init() { setMainWindow(new Window()); } }
The view should look something like that:
public class LoginView extends CustomComponent { private TextField login = new TextField("Login"); private TextField password = new TextField("Password"); public LoginView() { FormLayout layout = new FormLayout(); setCompositionRoot(layout); layout.addComponent(login); layout.addComponent(password); Button button = new Button("Login"); layout.addComponent(button); button.addListener(new ClickListener() { @Override public void buttonClick(ClickEvent event) { getApplication().getMainWindow().setContent(new MainView()); } }); } }
Important notes:
- MainView is another custom component with the components we want displayed
- don't forget the separation of concerns, the switching behavior mixed in the GUI code is shown only for readability purposes
- login in and out should perhaps be designed at the application level so we could call getApplication().login()
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