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Java Help Files - The Code
(Post 2 of 4 )

Find below a complete listing of the code in our class. Have a quick look at it now, but don’t worry if you don’t understand all the details. Some basic knowledge of Java is assumed so not all the lines of code will be discussed. Relevant sections will be explained in detail.

1://////////////////////////////////////////////////////////////////
2:/**
3:* This class creates a frame with a JEditorPane for loading HTML
4:* help files
5:*/
6://package goes here
7:import java.io.*;
8:import javax.swing.event.*;
9:import javax.swing.*;
10:import java.net.*;
11:import java.awt.event.*;
12:import java.awt.*;
13:
14ublic class HelpWindow extends JFrame implements ActionListener{
15: private final int WIDTH = 600;
16: private final int HEIGHT = 400;
17: private JEditorPane editorpane;
18: private URL helpURL;
19://////////////////////////////////////////////////////////////////
20:/**
21: * HelpWindow constructor
22: * @param String and URL
23: */
24ublic HelpWindow(String title, URL hlpURL) {
25: super(title);
26: helpURL = hlpURL;
27: editorpane = new JEditorPane();
28: editorpane.setEditable(false);
29: try {
30: editorpane.setPage(helpURL);
31: } catch (Exception ex) {
32: ex.printStackTrace();
33: }
34: //anonymous inner listener
35: editorpane.addHyperlinkListener(new HyperlinkListener() {
36: public void hyperlinkUpdate(HyperlinkEvent ev) {
37: try {
38: if (ev.getEventType() == HyperlinkEvent.EventType.ACTIVATED) {
39: editorpane.setPage(ev.getURL());
40: }
41: } catch (IOException ex) {
42: //put message in window
43: ex.printStackTrace();
44: }
45: }
46: });
47: getContentPane().add(new JScrollPane(editorpane));
48: addButtons();
49: // no need for listener just dispose
50: setDefaultCloseOperation(DISPOSE_ON_CLOSE);
51: // dynamically set location
52: calculateLocation();
53: setVisible(true);
54: // end constructor
55:}
56:/**
57: * An Actionlistener so must implement this method
58: *
59: */
60ublic void actionPerformed(ActionEvent e) {
61: String strAction = e.getActionCommand();
62: URL tempURL;
63: try {
64: if (strAction == "Contents") {
65: tempURL = editorpane.getPage();
66: editorpane.setPage(helpURL);
67: }
68: if (strAction == "Close") {
69: // more portable if delegated
70: processWindowEvent(new WindowEvent(this,
71: WindowEvent.WINDOW_CLOSING));
72: }
73: } catch (IOException ex) {
74: ex.printStackTrace();
75: }
76:}
77:/**
78: * add buttons at the south
79: */
80rivate void addButtons() {
81: JButton btncontents = new JButton("Contents");
82: btncontents.addActionListener(this);
83: JButton btnclose = new JButton("Close");
84: btnclose.addActionListener(this);
85: //put into JPanel
86: JPanel panebuttons = new JPanel();
87: panebuttons.add(btncontents);
88: panebuttons.add(btnclose);
89: //add panel south
90: getContentPane().add(panebuttons, BorderLayout.SOUTH);
91:}
92:/**
93: * locate in middle of screen
94: */
95rivate void calculateLocation() {
96: Dimension screendim = Toolkit.getDefaultToolkit().getScreenSize();
97: setSize(new Dimension(WIDTH, HEIGHT));
98: int locationx = (screendim.width - WIDTH) / 2;
99: int locationy = (screendim.height - HEIGHT) / 2;
100: setLocation(locationx, locationy);
101:}
102ublic static void main(String [] args){
103: URL index = ClassLoader.getSystemResource("index.html");
104: new HelpWindow("Test", index);
105:
106:}
107:}//end HelpWindow class
108:////////////////////////////////////////////////////////////////