Re: Design issue in swing application

From:
Fencer <no.i.dont@want.mail.from.spammers.com>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 17 Feb 2010 19:09:31 +0100
Message-ID:
<7u2pmsFb9qU1@mid.individual.net>
On 2010-02-17 18:48, Lew wrote:

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.


Ah, I learned something useful there! I usually initialize to null even
though that is done automatically but now you taught me that if I dont
initalize to null I can use final! Thank you.

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.

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