Re: Design issue in swing application

From:

Lew <noone@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 17 Feb 2010 12:48:09 -0500

Message-ID:

<hlha4q$h2l$1@news.albasani.net>

Fencer wrote:

package gui;

import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.border.TitledBorder;

public class WelcomePanel extends JPanel {

   private static final long serialVersionUID = 1596841645688614873L;

   public WelcomePanel(final CenteredGroup inst) {
      this.inst = inst;

      setPreferredSize(new Dimension(480, 100));
      setBorder(new TitledBorder("Start a new session by opening a
BioModel or load a previously saved session"));
      setLayout(new GridBagLayout());

      initButtons();
   }

   private void initButtons() {
      final CenteredGroup inst2 = this.inst;

^
You don't need this line.

      b1 = new JButton("Open BioModel");

      b1.addActionListener(new ActionListener() {
            @Override public void actionPerformed(ActionEvent e) {
               inst2.eventOpenBioModel();
            }});

      b2 = new JButton("Load Saved Session");

      b2.addActionListener(new ActionListener() {
            @Override public void actionPerformed(ActionEvent e) {
               inst2.eventLoadSavedSession();
            }});

      addButtonsToGroupPanel(b1, b2);
   }

   private void addButtonsToGroupPanel(JButton b1, JButton b2) {
      GridBagConstraints gbc = new GridBagConstraints();

      gbc.gridx = 0;
      gbc.gridy = 0;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.weightx = 0.5;
      gbc.weighty = 0;
      gbc.anchor = GridBagConstraints.CENTER;
      gbc.fill = GridBagConstraints.NONE;

      add(b1, gbc);

      gbc.gridx = 1;

      add(b2, gbc);
   }

   private CenteredGroup inst = null;

   private JButton b1 = null;
   private JButton b2 = null;
}

Why do you initialize these instance members to 'null' when a) the language
already does that anyway, and b) you initialize them to non-'null' values in
your constructor anyway?

Just curious.

It's a matter of style, but personally I find placement of member variable
declarations at the top to be clearer than at the bottom. For example, in
this code it would make it more obvious that you are assign values to those
instance variables three times apiece.

For this particular class, where the 'CenteredGroup' and the two 'JButton's
each need exactly one value, you should declare those variables 'final' and
assign their 'new' values in the constructor rather than a separate method.

--
Lew