Re: Design issue in swing application
On 2010-02-17 18:52, markspace wrote:
Lew gave some good links and advice. Here's the same stuff in a slightly
different format.
Normally, the Controller has references to the View and the Model, not
the other way around.
public class Controller {
View view;
Model model;
public Controller ( View view, Model model ) {
this.view = view;
this.model = model;
...
}
...
}
View would be some interface that this controller knows how to deal
with. Your View would be named "WelcomeScreen" or something like that;
this controller might be called a "WelcomeController". The
implementation of the view would be a JPanel or JFrame but your
controller wouldn't care about that.
The thing that receives the user interaction is the controller too. The
view only knows about the controller via a call back, so that needs to
be set.
public Controller ( View view, Model model ) {
this.view = view;
this.model = model;
this.view.addLoadFileActionListener( new ActionListener() {
@Override
public actionPerformed( final ActionEvent e ) {
loadFile( e );
}
}
...
}
loadFile( ActionEvent e ) {
... show JFileDialog here...
Based on this code, I wrote a simple application pasted below. It
doesn't actually have a model because I wanted to keep things as short
as possible. Also, my controller knows about Swing in this
implementation, just wanted to say that right away. It's not going to be
perfect but I hope to have my application to incorporate some of the
spirit behind MVC at least. :-)
Something that worries me with the code below is that the class holding
the frame, AppEntry, which also serves as the entry point of the
application, isn't a view itself. Instead it creates my single view and
a single controller. Say I add a menu bar and status bar (a JLabel) to
the frame, those would also be views known about some controller?
The application I am attempting to write is a bioinformatics application
where I envision having a menu, a status bar, a welcome view when the
program isn't not working on an bioinformatic model and a data view when
the program is indeed working with a bioinformatic model and I haven't
figured out how to incorporate that into MVC.
Say a user starts the application and is greeted by the welcome view.
The user wants to load a biomodel so he or she clicks the corresponding
button. In my case the controller knows about swing and it detects the
button click through its anonymous inner ActionListener class. The
controller shows a file picker allowing the user to select the biomodel
he or she desires. This biomodel is passed to the model which does a lot
of processing on it to build a tree structure. I won't go into details
but this is by far the most complicated thing I will have in my
application. This tree structure is supposed to be displayed by another
view, let's call it the data view. So my model needs to pass display
data in a format that the data view can understand and then tell my
AppEntry class, which holds the frame, to create a new data view and
show that instead of the welcome view. All this through some controller
somehow. I'm not sure how to build this.
/* AppEntry.java start */
package main;
import java.awt.EventQueue;
import javax.swing.JFrame;
public class AppEntry {
public AppEntry() {
frame = new JFrame("MVC attempt");
frame.setSize(640, 480);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
welcomePanel = new WelcomeImpl();
frame.add(welcomePanel);
controller = new Controller(welcomePanel);
}
public void show() {
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
new AppEntry().show();
}
});
}
private final JFrame frame;
private final WelcomeImpl welcomePanel;
private final Controller controller;
}
/* AppEntry.java end */
/* Welcome.java start */
package main;
import java.awt.event.ActionListener;
public interface Welcome {
void addB1ActionListener(ActionListener actionListener);
}
/* Welcome.java end */
/* WelcomeImpl.java start */
package main;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
public class WelcomeImpl extends JPanel implements Welcome {
private static final long serialVersionUID = -8645551859827091979L;
public WelcomeImpl() {
b1 = new JButton("b1");
add(b1);
}
public void addB1ActionListener(ActionListener actionListener) {
b1.addActionListener(actionListener);
}
private final JButton b1;
}
/* WelcomeImpl.java end */
/* Controller.java start */
package main;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Controller {
public Controller(Welcome welcomeView) {
this.welcomeView = welcomeView;
this.welcomeView.addB1ActionListener(new ActionListener() {
@Override public void actionPerformed(ActionEvent arg0) {
System.out.println("Show file selection dialog, send
file to model?");
}});
}
private Welcome welcomeView;
}
/* Controller.java end */
It's probably crap and I probably haven't read enough, but as I said I
want to incorporate some of the ideas of MVC into this application. I
want to design it as best as I can but I don't have time to make it
perfect and its actual functionality, what the user sees, that's
complicated for me to write so I have to spend most of my time on that.
PS. The files my program operate on are called BioModels, not to be
confused with Model in MVC. :-)
- F