Mediator
Explain
Example
General Java Example
This example is a general example taken from [Execpc]
//
// Mediator.java
//
import java.io.*;
abstract class Mediator
{
public abstract void colleagueChanged(Colleague theChangedColleague);
public static void main(String args[])
{
ConcreteMediator aConcreteMediator = new ConcreteMediator();
aConcreteMediator.createConcreteMediator();
(aConcreteMediator.getOneColleage()).Display();
(aConcreteMediator.getNextColleague()).Display();
OneColleague newColleague = new OneColleague(aConcreteMediator, "OneColleague");
aConcreteMediator.colleagueChanged( (OneColleague)newColleague );
(aConcreteMediator.getOneColleage()).Display();
(aConcreteMediator.getNextColleague()).Display();
}
}
//
// Colleague.java
//
abstract class Colleague
{
private Mediator _aMediator;
public Colleague(Mediator m)
{
_aMediator = m;
}
public void changed()
{
_aMediator.colleagueChanged(this);
}
public Mediator getMediator()
{
return(_aMediator);
}
public abstract void Display();
}
//
// ConcreteMediator.java
//
class ConcreteMediator extends Mediator
{
private OneColleague _aOneColleague;
private NextColleague _aNextColleague;
public void colleagueChanged( Colleague theChangedColleague )
{
if ((( OneColleague)theChangedColleague).getSelection().equals( _aOneColleague.getSelection() ) )
{
_aNextColleague.setText( _aOneColleague.getSelection() );
}
}
public void createConcreteMediator()
{
_aOneColleague = new OneColleague(this, "OneColleague");
_aNextColleague = new NextColleague(this, "NextColleague");
}
public OneColleague getOneColleage()
{
return(_aOneColleague);
}
public NextColleague getNextColleague()
{
return(_aNextColleague);
}
}
//
// OneColleague.java
//
class OneColleague extends Colleague
{
private String _text;
public OneColleague(Mediator m, String t)
{
super( m );
_text = t;
}
public void setText(String text)
{
_text = text;
}
public String getSelection()
{
return(_text);
}
public void Display()
{
System.out.println("OneColleague = " + _text);
}
}
LimeWire
LimeWire uses several mediators in their coding. This Mediator is used to control the tip of the day window in limewire.
package com.limegroup.gnutella.gui;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
import java.util.ResourceBundle;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComponent;
import javax.swing.JDialog;
import javax.swing.JEditorPane;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import com.limegroup.gnutella.gui.themes.ThemeFileHandler;
import com.limegroup.gnutella.gui.themes.ThemeMediator;
import com.limegroup.gnutella.gui.themes.ThemeObserver;
import com.limegroup.gnutella.settings.StartupSettings;
import com.limegroup.gnutella.util.CommonUtils;
public final class TipOfTheDayMediator implements ThemeObserver {
/**
* The instance of this class.
*/
private static TipOfTheDayMediator _instance;
/**
* The title for the TOTD window.
*/
private static final String TOTD_TITLE =
GUIMediator.getStringResource("TOTD_TITLE");
/**
* The 'Did You Know' intro.
*/
private static final String TOTD_INTRO =
GUIMediator.getStringResource("TOTD_INTRODUCTION");
/**
* The 'Show Tips At Startup' string
*/
private static final String TOTD_STARTUP =
GUIMediator.getStringResource("TOTD_SHOW_AT_STARTUP");
/**
* 'Next'.
*/
private static final String TOTD_NEXT =
GUIMediator.getStringResource("TOTD_NEXT");
/**
* 'Previous'.
*/
private static final String TOTD_PREVIOUS =
GUIMediator.getStringResource("TOTD_PREVIOUS");
/**
* 'Close'.
*/
private static final String TOTD_CLOSE =
GUIMediator.getStringResource("TOTD_CLOSE");
/**
* The actual TOTD JDialog.
*/
private final JDialog _dialog = new JDialog();
/**
* The JTextComponent that displays the tip.
*/
private final JEditorPane _tipPane = new JEditorPane();
/**
* The 'Previous' JButton. Global so it can be
* enabled/disabled.
*/
private final JButton _previous;
/**
* The prefix to use for general tips.
*/
private static final String GENERAL = "GENERAL_";
/**
* The prefix to use for OSX tips.
*/
private static final String OSX = "OSX_";
/**
* The prefix to use for Windows tips.
*/
private static final String WINDOWS = "WINDOWS_";
/**
* The prefix to use for Linux tips.
*/
private static final String LINUX = "LINUX_";
/**
* The prefix to use for other all other OS' tips.
*/
private static final String OTHER = "OTHER_";
/**
* The prefix to use for non OSX tips.
*/
private static final String NOT_OSX = "NOT_OSX_";
/**
* The prefix to use for Pro tips.
*/
private static final String PRO = "PRO_";
/**
* The prefix to use for Free tips.
*/
private static final String FREE = "FREE_";
/**
* The list of keys that are valid in the resource bundle.
*/
private static final List<String> KEYS = new ArrayList<String>();
/**
* The index of the current tip.
*/
private static int _currentTip;
/**
* The foreground color to use for text.
*/
private static Color _foreground;
/**
* Whether or not we can display the TOTD dialog.
*/
private boolean _canDisplay = true;
/**
* Private constructor that initiates the appropriate things for the TOTD.
*/
private TipOfTheDayMediator() {
retrieveKeys();
_dialog.setModal(false);
_dialog.setResizable(false);
_dialog.setTitle(TOTD_TITLE);
GUIUtils.addHideAction((JComponent)_dialog.getContentPane());
// Previous' listener must be added here instead of
// in constructDialog because otherwise multiple
// listeners will be added when the theme changes.
_previous = new JButton(TOTD_PREVIOUS);
_previous.addActionListener(new PreviousTipListener());
constructDialog();
ThemeMediator.addThemeObserver(this);
}
/**
* Returns the sole instance of this class.
*/
public static synchronized TipOfTheDayMediator instance() {
if (_instance == null)
_instance = new TipOfTheDayMediator();
return _instance;
}
/**
* Redraws the whole dialog upon theme change.
*/
public void updateComponentTreeUI() {
SwingUtilities.updateComponentTreeUI(_dialog);
}
/**
* Causes the TOTD window to become visible.
*/
public void displayTipWindow() {
GUIMediator.safeInvokeLater(new Runnable() {
public void run() {
if (!_canDisplay)
return;
if (_dialog.isShowing()) {
_dialog.setVisible(false);
_dialog.setVisible(true);
_dialog.toFront();
return;
}
if (GUIMediator.isAppVisible())
_dialog.setLocationRelativeTo(GUIMediator.getAppFrame());
else
_dialog.setLocation(GUIMediator.getScreenCenterPoint(_dialog));
_dialog.setVisible(true);
if (!"text/html".equals(_tipPane.getContentType())) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
_tipPane.setContentType("text/html");
setText(getRandomTip());
}
});
}
_dialog.toFront();
}
});
}
/**
* Hides the TOTD dialogue window.
*/
public void hide() {
_dialog.setVisible(false);
}
/**
* Sets the text of the tip to a new tip.
*/
private void setText(String tip) {
int r = _foreground.getRed();
int g = _foreground.getGreen();
int b = _foreground.getBlue();
String foreHex = toHex(r) + toHex(g) + toHex(b);
_tipPane.setText("<html><body text='#" + foreHex + "'>" + tip + "</html>");
_tipPane.setCaretPosition(0);
}
/**
* Returns the int as a hex string.
*/
private String toHex(int i) {
String hex = Integer.toHexString(i).toUpperCase();
if(hex.length() == 1)
return "0" + hex;
else
return hex;
}
/**
* Iterates through all the tips' keys and stores the ones
* that are valid for this OS.
*/
private void retrieveKeys() {
ResourceBundle bundle = ResourceManager.getTOTDResourceBundle();
Enumeration<String> e = bundle.getKeys();
while(e.hasMoreElements()) {
final String k = e.nextElement();
if(k.startsWith(GENERAL))
KEYS.add(k);
else if(CommonUtils.isWindows() && k.startsWith(WINDOWS))
KEYS.add(k);
else if(CommonUtils.isMacOSX() && k.startsWith(OSX))
KEYS.add(k);
else if(CommonUtils.isLinux() && k.startsWith(LINUX))
KEYS.add(k);
else if(!CommonUtils.isWindows() &&
!CommonUtils.isMacOSX() &&
!CommonUtils.isLinux() &&
k.startsWith(OTHER))
KEYS.add(k);
else if(!CommonUtils.isMacOSX() && k.startsWith(NOT_OSX))
KEYS.add(k);
else if(CommonUtils.isPro() && k.startsWith(PRO))
KEYS.add(k);
else if(!CommonUtils.isPro() && k.startsWith(FREE))
KEYS.add(k);
}
// randomize the list.
Collections.shuffle(KEYS);
_currentTip = -1;
}
/**
* Retrieves a random tip and updates the _currentTip
* index to that tip.
*/
private String getRandomTip() {
// If this is our last key, reshuffle them.
if(_currentTip == KEYS.size() - 1) {
Collections.shuffle(KEYS);
_currentTip = -1;
} else if(_currentTip < -1)
_currentTip = -1;
String k = KEYS.get(++_currentTip);
if(_currentTip == 0)
_previous.setEnabled(false);
else
_previous.setEnabled(true);
ResourceBundle bundle = ResourceManager.getTOTDResourceBundle();
return bundle.getString(k);
}
/**
* Recreates the dialog box to update the theme.
*/
public void updateTheme() {
boolean wasShowing = _dialog.isShowing();
_dialog.setVisible(false);
_dialog.getContentPane().removeAll();
// Lower the size of the font in the TIP because
// it's going to get larger again.
Font tipFont = new Font(
_tipPane.getFont().getName(),
_tipPane.getFont().getStyle(),
_tipPane.getFont().getSize()-2);
_tipPane.setFont(tipFont);
constructDialog();
_tipPane.setContentType("text/html");
setText(getRandomTip());
if (wasShowing) {
_dialog.setVisible(true);
_dialog.toFront();
}
}
/**
* Builds the TOTD dialog.
*/
private void constructDialog() {
JPanel imagePanel = new JPanel();
imagePanel.setBorder(BorderFactory.createMatteBorder(0, 0, 0, 1,
ThemeFileHandler.TABLE_BACKGROUND_COLOR.getValue()));
JLabel img = new JLabel(GUIMediator.getThemeImage("question"));
imagePanel.add(img);
JPanel didYouKnowPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
JLabel didYouKnow = new JLabel(TOTD_INTRO);
Font didYouKnowFont = new Font(
"Dialog",
didYouKnow.getFont().getStyle(),
didYouKnow.getFont().getSize()+5);
didYouKnow.setFont(didYouKnowFont);
didYouKnowPanel.add(Box.createHorizontalStrut(3));
didYouKnowPanel.add(didYouKnow);
JPanel tipPanel = new JPanel();
_foreground = didYouKnow.getForeground();
tipPanel.setBorder(BorderFactory.createMatteBorder(1, 0, 0, 0,
ThemeFileHandler.TABLE_BACKGROUND_COLOR.getValue()));
// THE HTML ENGINE TAKES TOO LONG TO LOAD, SO WE MUST LOAD AS TEXT.
_tipPane.setContentType("text");
_tipPane.setEditable(false);
_tipPane.setBackground(tipPanel.getBackground());
Font tipFont = new Font(
"Dialog",
_tipPane.getFont().getStyle(),
_tipPane.getFont().getSize()+2);
_tipPane.setFont(tipFont);
_tipPane.addHyperlinkListener(GUIUtils.getHyperlinkListener());
_tipPane.setText(GUIMediator.getStringResource("TOTD_LOADING_TIPS"));
JScrollPane tipScroller = new JScrollPane(_tipPane);
tipScroller.setPreferredSize(new Dimension(400, 100));
tipScroller.setHorizontalScrollBarPolicy(
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
tipScroller.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
tipScroller.setBorder(null);
tipPanel.add(tipScroller);
BoxPanel rightTip = new BoxPanel();
rightTip.add(Box.createVerticalStrut(10));
rightTip.add(didYouKnowPanel);
rightTip.add(tipPanel);
JPanel wholeTip = new JPanel(new BorderLayout());
BoxPanel innerTip = new BoxPanel(BoxPanel.X_AXIS);
innerTip.add(imagePanel);
innerTip.add(rightTip);
innerTip.setBorder(BorderFactory.createLoweredBevelBorder());
wholeTip.add(Box.createHorizontalStrut(5), BorderLayout.WEST);
wholeTip.add(Box.createHorizontalStrut(5), BorderLayout.EAST);
wholeTip.add(Box.createVerticalStrut(5), BorderLayout.NORTH);
wholeTip.add(Box.createVerticalStrut(5), BorderLayout.SOUTH);
wholeTip.add(innerTip, BorderLayout.CENTER);
JPanel startupPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
JCheckBox showTips = new JCheckBox(TOTD_STARTUP);
showTips.setSelected(StartupSettings.SHOW_TOTD.getValue());
startupPanel.add(showTips);
JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
buttonPanel.add(_previous);
JButton next = new JButton(TOTD_NEXT);
buttonPanel.add(next);
JButton close = new JButton(TOTD_CLOSE);
buttonPanel.add(close);
JPanel navigation = new JPanel(new BorderLayout());
navigation.add(startupPanel, BorderLayout.WEST);
navigation.add(buttonPanel, BorderLayout.EAST);
showTips.addActionListener(new ShowTipListener());
next.addActionListener(new NextTipListener());
close.addActionListener(GUIUtils.getDisposeAction());
_dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
Container pane = _dialog.getContentPane();
pane.setLayout(new BoxLayout(pane, BoxLayout.Y_AXIS));
pane.add(wholeTip);
pane.add(Box.createVerticalStrut(5));
pane.add(navigation);
try {
_dialog.pack();
} catch(OutOfMemoryError oome) {
// who knows why it happens, but it's an internal error.
_canDisplay = false;
}
}
/**
* A listener for changing the state of the 'Show Tips on Startup'.
*/
private class ShowTipListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JCheckBox source = (JCheckBox)e.getSource();
StartupSettings.SHOW_TOTD.setValue(source.isSelected());
}
}
/**
* A listener for showing the next tip.
*/
private class NextTipListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
setText(getRandomTip());
}
}
/**
* A listener for showing the previous tip.
*/
private class PreviousTipListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
_currentTip = _currentTip - 2;
setText(getRandomTip());
}
}
}
