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Swing Chapter 25. (Special topics) JavaHelp. Easy for reading, Click here!

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Swing Chapter 25. (Special topics) JavaHelp. Easy for reading, Click here!

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Page: 3/6 



Previous Page Previous Page (2/6) - Next Page (4/6) Next Page
Subpages: 1. JavaHelp introduction
2. JavaHelp API overview
3. Basic JavaHelp example
4. Adding dialog-style help
5. Customizing the JHelp viewer
5. Creating a custom help view

25.3  Basic JavaHelp example

In this section we will add help capabilities to the introductory layout example from chapter 4, section 4.2, demonstrating five JInternalFrames each using a different layout manager. Each of these internal frames will receive a help topic placed in a separate HTML file. The HelpSet, map, TOC, and index files for this example were listed in section 25.1, and are used to create a HelpSet instance. We will assign String IDs to each internal frame using the CSH class and attach an InternalFrameListener to transfer focus to a the first component in a selected frame's content pane (because focus does not get transferred by default when a new internal frame is selected). By using a our HelpSet's HelpBroker we will then enable help on each frame, which can be invoked through the F1 key.

Figure 25.1 JavaHelp help viewer displaying the TOC view.

<<file figure25-1.gif>>

The Code: CommonLayoutsDemo.java

see \Chapter25\1

import java.awt.*;

import java.awt.event.*;

import java.util.*;

import java.io.*;

import java.net.*;

import javax.swing.*;

import javax.swing.border.*;

import javax.swing.event.*;

import javax.help.*;

public class CommonLayoutsDemo extends JFrame

{

  protected HelpSet m_hs;

  protected HelpBroker m_hb;

  static final String HELPSETNAME = "Help/Layout.hs";

  public CommonLayoutsDemo() {

    super("Layout Managers [Help]");

    setSize(500, 380);

    createHelp();

    InternalFrameAdapter activator = new InternalFrameAdapter() {

      public void internalFrameActivated(InternalFrameEvent e) {

        JInternalFrame fr = (JInternalFrame)e.getSource();

        Component c = fr.getContentPane().getComponent(0);

        if (c != null)

          c.requestFocus();

      }

    };

    JDesktopPane desktop = new JDesktopPane();

    getContentPane().add(desktop);

    JInternalFrame fr1 =

      new JInternalFrame("FlowLayout", true, true);

    // Unchanged code from section 4.2

    CSH.setHelpIDString(fr1,"FlowLayout");

    fr1.addInternalFrameListener(activator);

    JInternalFrame fr2 =

      new JInternalFrame("GridLayout", true, true);

    // Unchanged code from section 4.2

    CSH.setHelpIDString(fr2,"GridLayout");

    fr2.addInternalFrameListener(activator);

    JInternalFrame fr3 =

      new JInternalFrame("BorderLayout", true, true);

    // Unchanged code from section 4.2

    CSH.setHelpIDString(fr3,"BorderLayout");

    fr3.addInternalFrameListener(activator);

    JInternalFrame fr4 =

      new JInternalFrame("BoxLayout - X", true, true);

    // Unchanged code from section 4.2

    CSH.setHelpIDString(fr4,"BoxLayout");

    fr4.addInternalFrameListener(activator);

    JInternalFrame fr5 =

      new JInternalFrame("BoxLayout - Y", true, true);

    // Unchanged code from section 4.2

    CSH.setHelpIDString(fr5,"BoxLayout");

    fr5.addInternalFrameListener(activator);

    // Unchanged code from section 4.2

  }

  public static void main(String argv[]) {

    new CommonLayoutsDemo ();

  }

  protected void createHelp() {

    ClassLoader loader = this.getClass().getClassLoader();

    URL url;

    try {

      url = HelpSet.findHelpSet(loader, HELPSETNAME);

      m_hs = new HelpSet(loader, url);

      m_hb = m_hs.createHelpBroker();

      m_hb.enableHelpKey(getRootPane(), "Frame", m_hs);

    }

    catch (Exception ex) { ex.printStackTrace(); }

  }

}

Understanding the Code

Class CommonLayoutsDemo

New instance variables:

HelpSet m_hs: used to manage the help data for this application.

HelpBroker m_hb: used to manage the help viewer for this application.

New class variable:

String HELPSETNAME: the path and name of the HelpSet file relative to the location of this class.

The CommonLayoutsDemo constructor calls our custom createHelp() method to initialize JavaHelp functionality (see below). Each JInternalFrame is associated with a proper help ID using the CSH.setHelpIDString() method.

An InternalFrameAdapter (implementation of InternalFrameListener--see chapter 16) is used to detect whenever an internal frame is acivated, and transfer focus to the first component within its content pane. This is done because even though JInternalFrame can be activated by a mouse click over it's surface, this does not necessarily transfer focus to it. The focus may still belong to the component in the previously active JInternalFrame. This causes undesirable effects with JavaHelp because in this case we need to show a help topic based on the currently selected frame. By manually transfering focus to a child of the active JInternalFrame the correct help topic will be displayed when help is invoked. Thus, we add an instance of this listener to each internal frame.

The createHelp() method retrieves the URL corresponding to the help set for this application, and instantiates our HelpSet and HelpBroker instance variables. The enableHelpKey() method enables help functionality using the F1 key, and sets the default topic ID to "Frame" on the application's JRootPane.

Running the Code

Activate one of the internal frames and press F1. Figure 25.1 shows the JavaHelp help viewer displaying the help topic associated with the currently active internal frame. Explore and become familiar with the navigation functionality provided by the help viewer.



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