Develop Reference

Should action listeners be in the class they apply to?

I'm programming a web browser with multiple classes. One class is "navbar" which holds most of the buttons such as search, back, forward, etc.
The navbar class has action listeners which, when the search button is pressed, become active, and lead to the production of a URL, which needs to be passed to the JEditorPane, but the editor pane is in a different class, "editor".
It does not make sense for an editor to be instantiated inside navbar, so how can i pass the variable from the navbar class to the editor class?
Is it okay to use statics in this situation?

Why not simply give the nav bar a reference to the editor? This could be done in the constructor, if the editor is instantiated first, or via getter/setter pair (actually, only the setter is really needed...). If the nav bar has such a reference, it can call the appropriate methods from within the listener implementation.
class Editor { ... }
class NavBar implements ActionListener
{
public NavBar(Editor editor)
{
myEditor = editor;
}
public void actionPerformed (ActionEvent e)
{
// call methods of myEditor
}
private Editor myEditor;
}
Editor theEditor = new Editor();
NavBar theNavBar = new NavBar(theEditor);

You can use some kind of intermediate interface between these, typically a service like layer. Which is basically what the observer pattern is as well. The editor could list events the navbar produces, but that also means later on you could also catch these events in other components

My GUI will not display when I hit run in NetBeans

When I select "run" in Netbeans, my GUI does not display. It just displays a box on the bottom of the screen that says "Build successful".
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package modelrange;
import javax.swing.DefaultBoundedRangeModel;
public class RangedModel extends javax.swing.JPanel {
DefaultBoundedRangeModel myModel;
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new RangedModel().setVisible(true);
}
});
}
/**
* Creates new form RangedModel
*/
public RangedModel() {
myModel = new DefaultBoundedRangeModel(123, 100, 0, 1000);
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
private void initComponents() {
This is just the automated netbeans code from the GUI builder (edited out for the post)
}

JPanel forms are not created with main methods, in GUI Builder, which you do need.
JPanel is not a top-level container, which you do need to run a Swing app.
A top-level container is, for instance, a JFrame. So you should have created a JFrame form instead of a JPanel form. When you do this in Netbeans GUI Builder, a main method will be provided for you.
A simple fix would be just to create a new JFrame form, then just drag and drop the JPanel form to the JFrame form, as seen here, get rid of the main method in your JPanel form, then run the JFrame form class.
You may also need to set/change the Main class to the new JFrame form you just created. You can that by looking at this answer

First of all, you are extending JPanel, it's wrong because as peeskillet wrote at points 2 and 3.
Kind of top-level container are:
JFrame : the window with the bar
JWindow : the window without bar
JDialog : the window usually used to create option window
So you have to extend one of them, probably the first.
Than in this top-level container you can create JPanel, one or more, everyone will be a container of another object which will be the contenent.
Morover, remember to setVisible every JPanel that you implement and also the top-level container.
Useful links:
icon in JButton is not shown at the running of the program, what could be?
Java Swing: multiple windows
What's the difference between the implements & extends keywords in Java

change JPanel to JFrame. It will work.

Follow path YourProject/packacge which your java file is in
then,
You can right click to your project then click from over there "run file".This worked for me.

If you work in NetBeans, after building, check that you are running the file you need from the project. To do this, press shift + F6

Is it possible to add a message bar/ toolbar at the bottom of a titleareadialog?

With my TitleAreaDialog is it possible to add a area or a bar across the bottom, below the buttons. That a message can be displayed to the users, when a operation is taking place.
Here is a example of what I am referring to

AFAIK, this is not possible for JFace Dialogs. Depending on what exactly you are doing, you might want to have a look at JFace ApplicationWindow. This class has a method addStatusLine(). You would have to override the following method:
#Override
protected StatusLineManager createStatusLineManager() {
StatusLineManager statusLineManager = new StatusLineManager();
statusLineManager.setMessage(null, "YOUR_MESSAGE");
return statusLineManager;
}
You can change the text with:
getStatusLineManager().setMessage("YOUR_NEW_MESSAGE");
Here is an excellent overview of the ApplicationWindow class.

AbstractAction as WindowListener

I'm trying to separate function from state in my GUI application by the use of Action objects. I've been successful in using these to create menu items and buttons that have the same functionality.
My problem is this: I want to have the same Action for both the 'exit' item in my menu and the close button of the frame.
Currently I've been able to solve it by adding the following WindowListener to the frame:
private class MainWindowListener extends WindowAdapter {
#Override
public void windowClosing(WindowEvent e) {
new ExitAction(model).actionPerformed(new ActionEvent(e.getSource(), e.getID(), "Exit"));
}
}
Isn't there a simpler more straightforward way to do this?

Forwarding events is handy, but you can also use dispatchEvent(), as shown here.
Addendum: More examples that use Action are shown below.
LinePanel which connects buttons and keys.
ScrollAction which leverages existing Swing actions.
KeyPadPanel which illustrates forwarding actions.
GraphPanel which shows graph editor actions in a tool bar.

Why doesn't my Wicket Panel rerender after changing the default model?

When the page with the MessagePanel first renders, the message and the approve link render perfectly. When I click the approve link, all the business logic works as desired, the getNextMessage() method returns the appropriate object, but the message panel does not update on the page in the browser. That is, the message body Label does not update.
JPAEntityModel extends LoadableDetachableModel.
What am I missing? And how do I fix it?
public class MessagePanel(String id, IModel<Message> messageModel) extends Panel {
super(id, messageModel);
add(new Label("messageText", new PropertyModel<Message>(getModelObject(), Message.BODY_FIELD)));
add(new IndicatingAjaxFallbackLink<User>("approveLink", new JPAEntityModel<User> (getActiveUser())) {
#Override
public void onClick(AjaxRequestTarget target) {
Message nextMessage = getNextMessage();
MessagePanel.this.setDefaultModel(new JPAEntityModel<Message>(nextMessage));
target.add(MessagePanel.this);
}
});
setOutputMarkupId(true);
}

It is because you're not using the model properly.
This line takes the value of the panel's model object, as it is set during construction, and uses it to create the component model.
add(new Label("messageText", new PropertyModel<Message>(getModelObject(), Message.BODY_FIELD)));
To make matters worse, when you click the link, the panel is given a new model:
MessagePanel.this.setDefaultModel(new JPAEntityModel<Message>(nextMessage));
But this obviously doesn't affect the model of the label, as it is already set to refer to the original value.
So there are two things you need to change to make it work. First off, your label model should use your panel model directly:
new Model<Message>() {
#Override
public Message getObject() {
return MessagePanel.this.getModelObject().getMessage(); //or something similar
}
}
(Note: the code above isn't necessarily the best solution, but it is a working solution that demonstrates how models can be used dynamically.)
And ideally you shouldn't replace the model when you click the link, just change the model object. If you need a custom model class (JPAEntityModel), you shouldn't be accepting a pre-constructed model in the panel constructor anyway, just the first message object. The reason being the current implementation doesn't enforce the use of JPAEntityModel from the start, only after the first click of the link.

Can you try calling MessagePanel.this.modelChanged() before adding it to the target?

You must use call setOutputMarkupId(true) within you MessagePanel. The panel needs to have a markup identifier to be able to update the markup DOM in the browser.