Trail: Deployment
Lesson: Java Web Start

显示自定义加载进度指示器

A Java Web Start application can display a customized loading progress indicator that shows the progress of download of the application's resources.

Consider the Weather application and the CustomProgress class to understand how to implement a customized loading progress indicator for a Java Web Start application. For the purpose of demonstrating a large and prolonged download, this Java Web Start application's JAR file has been artificially inflated and the customprogress_webstart.jnlp file specifies additional JAR files as resources.

Developing a Customized Loading Progress Indicator

To develop a customized loading progress indicator for your Java Web Start application, create a class that implements the DownloadServiceListener interface.

The constructor of the loading progress indicator class should not have any parameters.

import javax.jnlp.DownloadServiceListener;
import java.awt.Container;
import java.applet.AppletStub;
import netscape.javascript.*;
// ...
public class CustomProgress
        implements DownloadServiceListener {   
    JFrame frame = null;
    JProgressBar progressBar = null;
    boolean uiCreated = false;

    public CustomProgress() {
    }
...
}

The following code snippet shows how to build the UI for the loading progress indicator:

private void create() {
    JPanel top = createComponents();
    frame = new JFrame(); // top level custom progress
                          // indicator UI
    frame.getContentPane().add(top,
                               BorderLayout.CENTER);
    frame.setBounds(300,300,400,300);
    frame.pack();
    updateProgressUI(0);
}

private JPanel createComponents() {
    JPanel top = new JPanel();
    top.setBackground(Color.WHITE);
    top.setLayout(new BorderLayout(20, 20));
 
    String lblText =
        "<html><font color=green size=+2" +
        ">JDK Documentation</font><br/> " +
        "The one-stop shop for Java enlightenment! <br/></html>";
    JLabel lbl = new JLabel(lblText);
    top.add(lbl, BorderLayout.NORTH);
    ...
    progressBar = new JProgressBar(0, 100);
    progressBar.setValue(0);
    progressBar.setStringPainted(true);
    top.add(progressBar, BorderLayout.SOUTH);

    return top;
}

Create and update the loading progress indicator in the following methods based on the overallPercent argument. These methods are invoked regularly by the Java Web Start software to communicate the progress of the application's download. Java Web Start software will always send a message when download and validation of resources is 100% complete.

public void progress(URL url, String version, long readSoFar,
                     long total, int overallPercent) {        
    updateProgressUI(overallPercent);

}

public void upgradingArchive(java.net.URL url,
                  java.lang.String version,
                  int patchPercent,
                  int overallPercent) {
    updateProgressUI(overallPercent);
}

public void validating(java.net.URL url,
            java.lang.String version,
            long entry,
            long total,
            int overallPercent) {
    updateProgressUI(overallPercent);
}

private void updateProgressUI(int overallPercent) {
    if (overallPercent > 0 && overallPercent < 99) {
        if (!uiCreated) {
            uiCreated = true;
            // create custom progress indicator's
            // UI only if there is more work to do,
            // meaning overallPercent > 0 and
            // < 100 this prevents flashing when
            // RIA is loaded from cache
            create();
        }
        progressBar.setValue(overallPercent);
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                frame.setVisible(true);
            }
        });
    } else {
        // hide frame when overallPercent is
        // above 99
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                frame.setVisible(false);
                frame.dispose();
            }
        });
    }
}

Compile the loading progress indicator class and build a JAR file with all the resources needed to display the loading progress indicator. Include the <your JRE directory>/lib/javaws.jar file in your classpath to enable compilation.

The loading progress indicator class is now ready for use. The next step is to specify this loading progress indicator JAR file as your Java Web Start application's progress indicator.

Specifying a Customized Loading Progress Indicator for a Java Web Start Application

To specify a customized loading progress indicator for a Java Web Start application, include the following information in the application's JNLP file:

jar tag with the download="progress" attribute
progress-class attribute with the fully qualified name of the customized loading progress class.

The following code snippet from the customprogress_webstart.jnlp file displays the usage of the download="progress" and progress-class attributes.

<jnlp spec="1.0+" codebase=
  "https://docs.oracle.com/javase/tutorialJWS/samples/deployment" 
   href="customprogress_webstartJWSProject/customprogress_webstart.jnlp">
  <!-- ... -->
  <resources>
    <j2se version="1.7+"/>
    <jar href=
      "webstart_AppWithCustomProgressIndicator/webstart_AppWithCustomProgressIndicator.jar" />
    <jar href=
      "webstart_CustomProgressIndicator/webstart_CustomProgressIndicator.jar"
         download="progress" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/IconDemo.jar" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/SplitPaneDemo.jar" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/SplitPaneDemo2.jar" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/TextBatchPrintingDemo.jar" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/ToolBarDemo.jar" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/ToolBarDemo2.jar" />
    <jar href=
      "webstart_AppWithCustomProgressIndicator/lib/SwingSet2.jar" />
  </resources>
  <application-desc 
      main-class="customprogressindicatordemo.Main"
      progress-class="customprogressindicator.CustomProgress"
  />
  <!-- ... -->
</jnlp>

Deploy the Java Web Start application in a web page. Open JavaWebStartAppPage.html in a web browser to view the customized loading progress indicator for the Weather application.

注意: To view the example properly, you need to install at least the Java SE Development Kit (JDK) 6 update 18 release.

注意: If you have viewed this Java Web Start application before, clear your cache by using the Java Control Panel before viewing the application again. You will not be able to see a progress indicator for a previously cached application.

注意: If you don't see the example running, you might need to enable the JavaScript interpreter in your browser so that the Deployment Toolkit script can function properly.

Download source codefor the Java Web Start Application With Customized Loading Progress Indicator example to experiment further.

See the Customizing the Loading Experience topic for more information about customizing the rich Internet application (RIA) loading experience.