For years, the Java programming language has dominated the development landscape of server-based applications. In the early days of the language's development, it was touted as a solution for developing cross-platform desktop applications. After end users and the developer community demanded something more than the Abstract Window Toolkit (AWT), Sun Microsystems introduced the Java Foundation Classes (JFC), also known as Swing, to entice developers to reconsider the Java language for developing GUI applications. While Swing does provide a mature and proven model for developing client-side applications, it still misses the visual appeal and operation of native applications.

Before the development and introduction of the SWT, industry pundits and developers alike had pronounced the Java language dead for the development of desktop applications. SWT is beginning to breathe new life into the opportunity of client-side Java by giving developers a framework to create applications that mimic the full fidelity of native applications. Unlike its predecessors (AWT and JFC, for example), SWT provides developers a platform-independent API that is tightly integrated with the operating system's native windowing environment.

While the Eclipse Project is traditionally thought as of an open source integrated development environment (IDE) for Java technology, the project's scope is much broader. On the front page of Eclipse's Web site, Eclipse is described as "... a kind of universal tool platform -- an open extensible IDE for anything and nothing in particular."

While Eclipse was used during the development of the sample application provided in this article, we'll focus on demonstrating how to use ActiveX controls within the context of a stand-alone application. For more information and background on the Eclipse Project, see the Resources.

PDF viewer application

Before we review the code and implementation details of how to integrate ActiveX controls into an SWT application, let's review the purpose and structure of the included sample application. The application is a simple PDF viewer that allows users to view and interact with a PDF file using Adobe's Acrobat Reader control. A user can browse his hard drive, locate a file, and view PDF documents within an SWT application, as shown in Figure 1.

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Environment requirements

You can download the sample PDF viewer application (see Resources). To test the PDF viewer application, your environment must meet the following minimum requirements:

• Microsoft Windows operating system
• Java 2 SDK, Standard Edition 1.4.1 or later
• Apache Ant V1.5.2 or later
• Adobe Acrobat Reader V5.0

Although attention has been given to make the Ant build script cross-platform, the PDF viewer application has been tested and verified only on Microsoft® Windows XP. Let's get started by installing and setting up the sample application.

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Installing and building the PDF viewer application

To install and build the PDF viewer application, complete the following:

1. Download the source code package.
2. Unzip the pdfviewer.zip file into a temporary directory.
3. Execute the following command within the newly created directory: ant clean.
4. Execute the following command within the newly created directory: ant.

If your environment meets the requirements and is properly configured, you should see something similar to Listing 1

                
Buildfile: build.xml

init:
    [mkdir] Created dir: D:\PDFViewer\dist

compile-common:

compile-module:
    [echo] Compiling ...
    [mkdir] Created dir: D:\PDFViewer\build
    [mkdir] Created dir: D:\PDFViewer\build\classes
    [javac] Compiling 5 source files to D:\PDFViewer\build\classes

package-common:
      [jar] Building jar: D:\PDFViewer\dist\pdfviewer.jar

default:

BUILD SUCCESSFUL

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Using an ActiveX control

Now that we've covered the basics for the PDF viewer application, let's review how to integrate and use an ActiveX control within an SWT application. Since our purpose here is to cover ActiveX integration, we won't review how to create a stand-alone SWT application or how to use ActiveX controls in Microsoft Windows.

Listing 2 outlines the basic structure of the PDFViewer class and demonstrates how an ActiveX control is integrated into an SWT application.

                
1   public class PDFViewer extendsApplicationWindow
2   {
3      private OleControlSite site;
4      private OleAutomation auto;
5
6      public PDFViewer()
7      {
8         super(null);
9         this.addMenuBar();
10      }
11
12      protected ControlcreateContents(Composite parent)
13      {
14         Shell shell = this.getShell();
15         shell.setText("PDFViewer");
16         shell.setSize(500, 450);
17
18         OleFrame frame = new OleFrame(shell, SWT.NONE);
19
20         try
21         {
22            site = new OleControlSite(frame,SWT.NONE, "PDF.PdfCtrl.5");
23            auto = new OleAutomation(site);
24            
25   ...

Let's step through this code snippet:

1. Whenever the application starts, a new instance of the PDFViewer class is created.
2. As shown on lines 3 and 4, we need to define two objects: OleControlSite and OleAutomation. The OleControlSite object variable handles the interaction with the ActiveX control. The OleAutomation object allows you to access properties and execute commands that are provided by the ActiveX control.
3. On line 18, an OleFrame object is defined. This object is the container for the ActiveX control and manages the control's lifecycle.
4. Line 22 instantiates the site variable using two arguments: the first argument contains a reference to an OleFrame, and the second argument contains a string that identifies the ActiveX control. A program identifier, found within the Windows Registry, uniquely identifies the control within Microsoft Windows.
5. Line 23 instantiates the site variable using a reference to an OleControlSite variable.

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Selecting a PDF document

Before the user can view a PDF document, he needs to select a PDF document from his workstation. The code below illustrates the objects and methods necessary to open a file dialog to the end user.

                
0  ?
1  public class OpenAction extends Action
2  {
3     ApplicationWindow window;
4
5     public OpenAction(ApplicationWindow w)
6     {
7           window = w;
8           this.setText("&Open...");
9
10          this.setToolTipText("Open a PDF document.");
11       }
12
13       public void run()
14       {
15       FileDialog dialog = new FileDialog(window.getShell());
16       dialog.open();
17
18       String file = dialog.getFilterPath()+"\\"+dialog.getFileName();
19
20       PDFViewer viewer = ((PDFViewer)window);
21
22       viewer.loadFile(file);
23
24       }
25    }

Let's review this code snippet:

1. Whenever a user selects Open from a menu bar, the run method on line 13 executes.
2. As shown on lines 15 and 16, a FileDialog object is created. As displayed in Figure 2, this object displays a native file dialog box to the user.
3. Line 18 constructs a string that contains the location of the PDF document on the user's workstation.
4. Line 20 casts the window object to a PDFViewer object.
5. Line 22 executes the loadFile method and passes in the location for the selected PDF document. We'll review the loadFile method in more detail in the next couple of sections.

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Listing an ActiveX's commands

Before we cover how the PDF document is displayed within the viewer application, it's helpful to understand what commands are actually available within the Adobe Acrobat Reader Active X (PDF.PdfCtrl.5) component. The sample code package includes a class developed by IBM®. This class lists all the public commands that an ActiveX control exposes.

To enumerate the commands for the PDF.PdfCtrl.5 control, execute the following command within the PDFViewer directory: ant activex. If your environment is properly configured, you should see something similar to Listing 4.

                
...
     [java]Functions for PDF.PdfCtrl.5 :
       
     [java]METHOD (id = 2) :
     [java]     Signature   : boolean LoadFile([] String fileName)
     [java]     Description : null
     [java]     Help File   : null
       
     [java]METHOD (id = 3) :
     [java]     Signature   : void setShowToolbar([] boolean On)
     [java]     Description : null
     [java]     Help File   : null
       
     [java]METHOD (id = 4) :
     [java]     Signature   : void gotoFirstPage()
     [java]     Description : null
     [java]     Help File   : null
     ...

To view the commands for any other ActiveX control, simply edit the build.xml file that is included with the source code and replace the class's argument with some other ActiveX's program identifier. The Ant target below illustrates the location to insert the control's program identifier.

                
...
      <target name="activex" depends="package-common">

            <java classname="Main" fork="true">

                     <jvmarg value="-Djava.library.path=${eclipse.dir}windows"/> 
                      <classpath>
                        <pathelement location="${dist.dir}/pdfviewer.jar"/>
                              <fileset dir="${eclipse.dir}" includes="*.jar"/>
                              <fileset dir="${eclipse.dir}windows" includes="*.jar"/>
                      </classpath>

                      <arg value="<insert some program identifier>"/> 

            </java>

      </target> 
...

The first command that was output from the class was LoadFile. Let's explore how to this command is utilized within the PDFViewer application.

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Executing an ActiveX command

Once the user selects a PDF document, the PDFViewer class needs to execute a command that it has exposed in the ActiveX control. The code Listing 6 illustrates the objects and methods necessary to have the ActiveX control load the user's selected PDF document.

                
0   ...
1   public void showPdfControl()
2   {
3      site.doVerb(OLE.OLEIVERB_SHOW);
4   }
5
6   public void loadFile(String file)
7   {
8      showPdfControl();
9
10      int[] rgdispid = auto.getIDsOfNames(newString[]{"LoadFile"});
11      int dispIdMember = rgdispid[0];
12
13      Variant[] rgvarg = new Variant[1]; 
14      rgvarg[0] = new Variant(file);
15
16      Variant pVarResult =auto.invoke(dispIdMember,rgvarg);
17   }
18...

Let's review this code snippet:

1. After a user selects a PDF file, the loadFile method on line 6 is executed.
2. Line 8 calls the showPdfControl method. Before an ActiveX control is visible within the application, the control must be activated using the doVerb command.
3. Lines 10 through 16 invoke the LoadFile command within the ActiveX control.

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Running the PDF viewer application

To test out and run the PDF viewer application, complete the following steps:

1. Execute the following command within the directory where you unpacked the source code: ant run.
2. Upon execution of the Ant script, the PDF viewer application should appear.
3. Select Open from the File menu to select a PDF file from your workstation. The selected PDF document is rendered.

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Summary

The SWT library gives Java developers a powerful mechanism to integrate Microsoft Windows ActiveX controls into highly interactive client-side applications. With SWT's support for ActiveX controls and OLE documents, it's exciting to explore ways to create great-looking applications that integrate native widgets and components.

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Download

Information about download methods

Resources

Learn

• For more detail about SWT's support of ActiveX controls, check out ActiveX Support in SWT on the Eclipse Web site.
  
  
• Read "Using the Eclipse GUI outside the Eclipse Workbench, Part 1," Part 2, and Part 3.
  
  
• Read "Developing Eclipse plug-ins."
  
  
• Check out "C/C++ development with the Eclipse Platform" to learn more.
  
  
• Don't miss "XML development with the Eclipse Platform."
  
  

Get products and technologies

• Download the source code package for the sample PDF viewer application demonstrated in this article.
  
  
• Download Java 2 SDK, Standard Edition 1.4.1 from Sun Microsystems.
  
  
• Download Ant 1.5.3 or higher from the Apache Software Foundation.
  
  

About the author

Comments (Undergoing maintenance)

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Table of contents

• PDF viewer application
• Environment requirements
• Installing and building the PDF viewer application
• Using an ActiveX control
• Selecting a PDF document
• Listing an ActiveX's commands
• Executing an ActiveX command
• Running the PDF viewer application
• Summary
• Download
• Resources
• About the author
• Comments

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