How to access components outside its defined view?

General
1

Hi,

I’ve defined a MyUI class that adds a view defined by the MainView class:

public class MyUI extends UI implements ViewChangeListener {
....
getUI().getNavigator().addView("secure", new MainView());
....
}

The MainView class defines several components, but how to access those in other classes within the application?

Regards,
Gerard

2

Hi,

If your View is a component container, eg. a layout, you can use its API normally (eg. VerticalLayout.getComponent(index) etc). Or you can write getter methods yourself, this of course has the advantage that you can choose descriptive names. I recommend you store references to the views in the UI to be able to access them easier:

public class MyUI extends UI implements ViewChangeListener {

    private final MainView mainView = new MainView();
    ...
    getUI().getNavigator().addView("secure", mainView);
    ...
    doSomethingWith(mainView.getSomeComponent());
}
3

Hi,

Thanks for your response, but I’m afraid I don’t quite understand it!

If for example the MainView adds a menubar CustomComponent to the view using:

addComponent(menubar); and I want to access this menubar from another class!

I still don’t see how your answer fits in here, sorry?!

Regards,
Gerard

4

Hi Gerard,

Usually, it’s not good practice to introduce direct dependencies between your Views unless absolutely needed. What is the underlying problem that you are trying to solve?

5

Hi,

Thanks for trying to help me solve this issue which I think is a very basic one!

Well, I’ve as MyUI:

[code]
import javax.servlet.annotation.WebServlet;

import org.apache.shiro.SecurityUtils;
import org.apache.shiro.subject.Subject;

import biobank.view.ErrorView;
import biobank.view.LoginView;
import biobank.view.MainView;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.Component;
import com.vaadin.ui.UI;
import com.vaadin.navigator.Navigator;
import com.vaadin.navigator.ViewChangeListener;

@SuppressWarnings(“serial”)
@Theme(“mytheme”)
public class MyUI extends UI implements ViewChangeListener {

Navigator navigator;

@WebServlet(value = "/*", asyncSupported = true)
@VaadinServletConfiguration(productionMode = false, ui = MosaphenUI.class)
public static class Servlet extends VaadinServlet {
}

@Override
protected void init(VaadinRequest request) {

// Create a navigator to control the views
navigator = new Navigator(this, this);
navigator.addViewChangeListener(this);

    navigator.addView("", LoginView.class);
    if (SecurityUtils.getSubject().isAuthenticated()) {
        mv = new MainView();
        getUI().getNavigator().addView("secure", new MainView());
    }
    navigator.setErrorView(ErrorView.class);
}
....

[/code]MainView adds for example a menubar CustomComponent like:

public class MainView extends VerticalLayout implements View {

final private StatusBar statusbar = new StatusBar();
....
addComponent(statusbar);

…
}

The MainView consists of a menubar, mainpane and the statusbar. The mainpane contains a button, and a ClickEvent handler. Now when I click that button I want to update the statusbar. How can I refer to the statusbar component within this ClickEvent handler?

This is a simple example, it becomes even more challenging when one wants to update more than one component!

I can’t find any examples on the Vaadin site how to tackle this, so I suspect I do misunderstand some basic stuff here!

Regards,
Gerard

6

https://code.google.com/p/guava-libraries/wiki/EventBusExplained

Google Guava has ‘EventBus’. One object publishes, other objects subscribe.

7

For a real life example of using an Event Bus, you may want to look at how the refactored QuickTickets Dashboard works: https://github.com/vaadin/dashboard-demo

8

Hi,

Thanks for your suggestions, but that needs some study from my part, because this option is completely new to me!

Regards,
Gerard