Java实现MessageBox类

MessageBox类弹出Java应用程序的警告，错误。

package com.nova.colimas.install;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.*;
import java.awt.*;

public class MessageBox implements Runnable, ActionListener, WindowListener,
KeyListener {

// ---------- Private Fields ------------------------------
private ActionListener listener;

private JDialog dialog;

private String closeWindowCommand = "CloseRequested";

private String title;

private JFrame frame;

private boolean frameNotProvided;

private JPanel buttonPanel = new JPanel();

// ---------- Initialization ------------------------------
/**
* This convenience constructor is used to delare the listener that will be
* notified when a button is clicked. The listener must implement
* ActionListener.
*/
public MessageBox(ActionListener listener) {
this();
this.listener = listener;
}

/**
* This constructor is used for no listener, such as for a simple okay
* dialog.
*/
public MessageBox() {
}

// Unit test. Shows only simple features.
public static void main(String args[]) {
MessageBox box = new MessageBox();
box.setTitle("Test MessageBox");
box.askYesNo("Tell me now.\nDo you like Java?");
}

// ---------- Runnable Implementation ---------------------
/**
* This prevents the caller from blocking on ask(), which if this class is
* used on an awt event thread would cause a deadlock.
*/
public void run() {
dialog.setVisible(true);
}

// ---------- ActionListener Implementation ---------------
public void actionPerformed(ActionEvent evt) {
dialog.setVisible(false);
dialog.dispose();
if (frameNotProvided)
frame.dispose();
if (listener != null) {
listener.actionPerformed(evt);
}
}

// ---------- WindowListener Implementatons ---------------
public void windowClosing(WindowEvent evt) {
// User clicked on X or chose Close selection
fireCloseRequested();
}

public void windowClosed(WindowEvent evt) {
}

public void windowDeiconified(WindowEvent evt) {
}

public void windowIconified(WindowEvent evt) {
}

public void windowOpened(WindowEvent evt) {
}

public void windowActivated(WindowEvent evt) {
}

public void windowDeactivated(WindowEvent evt) {
}

// ---------- KeyListener Implementation ------------------
public void keyTyped(KeyEvent evt) {
}

public void keyPressed(KeyEvent evt) {
if (evt.getKeyCode() == KeyEvent.VK_ESCAPE) {
fireCloseRequested();
}
}

public void keyReleased(KeyEvent evt) {
}

private void fireCloseRequested() {
ActionEvent event = new ActionEvent(this, ActionEvent.ACTION_PERFORMED,
closeWindowCommand);
actionPerformed(event);
}

// ---------- Public Methods ------------------------------
/**
* This set the listener to be notified of button clicks and WindowClosing
* events.
*/
public void setActionListener(ActionListener listener) {
this.listener = listener;
}

public void setTitle(String title) {
this.title = title;
}

/**
* If a Frame is provided then it is used to instantiate the modal Dialog.
* Otherwise a temporary Frame is used. Providing a Frame will have the
* effect of putting the focus back on that Frame when the MessageBox is
* closed or a button is clicked.
*/
public void setFrame(JFrame frame) { // Optional
this.frame = frame;
}

/**
* Sets the ActionCommand used in the ActionEvent when the user attempts to
* close the window. The window may be closed by clicking on "X", choosing
* Close from the window menu, or pressing the Escape key. The default
* command is "CloseRequested", which is just what a Close choice button
* would probably have as a command.
*/
public void setCloseWindowCommand(String command) {
closeWindowCommand = command;
}

/**
* The
*
* @param label
* will be used for the button and the
* @param command
* will be returned to the listener.
*/
public void addChoice(String label, String command) {
JButton button = new JButton(label);
button.setActionCommand(command);
button.addActionListener(this);
button.addKeyListener(this);

buttonPanel.add(button);
}

/**
* A convenience method that assumes the command is the same as the label.
*/
public void addChoice(String label) {
addChoice(label, label);
}

/**
* One of the "ask" methods must be the last call when using a MessageBox.
* This is the simplest "ask" method. It presents the provided
*
* @param message.
*/
public void ask(String message) {
if (frame == null) {
frame = new JFrame();
frameNotProvided = true;
} else {
frameNotProvided = false;
}
dialog = new JDialog(frame, true); // Modal
dialog.addWindowListener(this);
dialog.addKeyListener(this);
dialog.setTitle(title);
dialog.setLayout(new BorderLayout(5, 5));

JPanel messagePanel = createMultiLinePanel(message);
JPanel centerPanel = new JPanel();
centerPanel.add(messagePanel);
dialog.add("Center", centerPanel);
dialog.add("South", buttonPanel);
dialog.pack();
enforceMinimumSize(dialog, 200, 100);
centerWindow(dialog);
Toolkit.getDefaultToolkit().beep();

// Start a new thread to show the dialog
Thread thread = new Thread(this);
thread.start();
}

/**
* Same as ask(String message) except adds an "Okay" button.
*/
public void askOkay(String message) {
addChoice("Okay");
ask(message);
}

/**
* Same as ask(String message) except adds "Yes" and "No" buttons.
*/
public void askYesNo(String message) {
addChoice("Yes");
addChoice("No");
ask(message);
}

// ---------- Private Methods -----------------------------
private JPanel createMultiLinePanel(String message) {
JPanel mainPanel = new JPanel();
GridBagLayout gbLayout = new GridBagLayout();
mainPanel.setLayout(gbLayout);
addMultilineString(message, mainPanel);
return mainPanel;
}

// There are a variaty of ways to do this....
private void addMultilineString(String message, Container container) {

GridBagConstraints constraints = getDefaultConstraints();
constraints.gridwidth = GridBagConstraints.REMAINDER;
// Insets() args are top, left, bottom, right
constraints.insets = new Insets(0, 0, 0, 0);
GridBagLayout gbLayout = (GridBagLayout) container.getLayout();

while (message.length() > 0) {
int newLineIndex = message.indexOf('\n');
String line;
if (newLineIndex >= 0) {
line = message.substring(0, newLineIndex);
message = message.substring(newLineIndex + 1);
} else {
line = message;
message = "";
}
JLabel label = new JLabel(line);
gbLayout.setConstraints(label, constraints);
container.add(label);
}
}

private GridBagConstraints getDefaultConstraints() {
GridBagConstraints constraints = new GridBagConstraints();
constraints.weightx = 1.0;
constraints.weighty = 1.0;
constraints.gridheight = 1; // One row high
// Insets() args are top, left, bottom, right
constraints.insets = new Insets(4, 4, 4, 4);
// fill of NONE means do not change size
constraints.fill = GridBagConstraints.NONE;
// WEST means align left
constraints.anchor = GridBagConstraints.WEST;

return constraints;
}

private void centerWindow(JDialog win) {
Dimension screenDim = Toolkit.getDefaultToolkit().getScreenSize();
// If larger than screen, reduce window width or height
if (screenDim.width < win.getSize().width) {
win.setSize(screenDim.width, win.getSize().height);
}
if (screenDim.height < win.getSize().height) {
win.setSize(win.getSize().width, screenDim.height);
}
// Center Frame, Dialogue or Window on screen
int x = (screenDim.width - win.getSize().width) / 2;
int y = (screenDim.height - win.getSize().height) / 2;
win.setLocation(x, y);
}

private void enforceMinimumSize(JDialog comp, int minWidth, int minHeight) {
if (comp.getSize().width < minWidth) {
comp.setSize(minWidth, comp.getSize().height);
}
if (comp.getSize().height < minHeight) {
comp.setSize(comp.getSize().width, minHeight);
}
}

} // End class

在调用它的WindowsMain类里添加一个Close按钮，点击Close按钮时调用MessageBox选择yes或no。

jCloseButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent e) {
//System.out.println("actionPerformed()"); // TODO Auto-generated Event stub actionPerformed()
MessageBox box = new MessageBox();
box.setTitle("Warning");
box.askYesNo("Do you really want to exit?");

//添加MessageBox的按钮事件Listener。
box.setActionListener(new java.awt.event.ActionListener(){
public void actionPerformed(java.awt.event.ActionEvent e){
JButton button=(JButton)e.getSource();
if(button.getText()=="Yes")
System.exit(0);
}
}
);
}
});