Java 中文官方教程 2022 版（十九）（4）

java.net.URL imageURL = myDemo.class.getResource("images/myImage.gif");
...
if (imageURL != null) {
    ImageIcon icon = new ImageIcon(imageURL);
}

java -cp  .;images.jar  MyDemo  [Microsoft Windows]
java -cp ".;images.jar" MyDemo  [UNIX-emulating shell on Microsoft
                                Windows — you must quote the path]
java -cp  .:images.jar  MyDemo  [UNIX]

java -cp .;MyDemo.jar;images.jar MyDemo  [Microsoft Windows]

java -jar MyAppPlusImages.jar
java -cp .;MyAppPlusImages.jar MyApp  [Microsoft Windows]

<?xml version="1.0" encoding="utf-8"?>
<!-- JNLP File for DragPictureDemo -->
<jnlp
  spec="1.0+"
  codebase="https://docs.oracle.com/javase/tutorialJWS/src/uiswing/misc/examples"
  href="DragPictureDemo.jnlp">
  <information>
    <title>DragPictureDemo</title>
    <vendor>The Java(tm) Tutorial: Sun Microsystems, Inc.</vendor>
    <homepage href="https://docs.oracle.com/javase/tutorial/uiswing/misc/examples/index.html#DragPictureDemo"/>
    <description>DragPictureDemo</description>
    <description kind="short">A demo showing how to install
        data transfer on a custom component.</description>
    <offline-allowed/>
  </information>
  <resources>
    <j2se version="1.6+"/>
    <jar href="allClasses.jar"/>
    <jar href="images.jar"/>
  </resources>
  <application-desc main-class="DragPictureDemo"/>
</jnlp>

/**
 * SwingWorker class that loads the images a background thread and calls publish
 * when a new one is ready to be displayed.
 *
 * We use Void as the first SwingWorker param as we do not need to return
 * anything from doInBackground().
 */
private SwingWorker<Void, ThumbnailAction> loadimages = new SwingWorker<Void, ThumbnailAction>() {
    /**
     * Creates full size and thumbnail versions of the target image files.
     */
    @Override
    protected Void doInBackground() throws Exception {
        for (int i = 0; i < imageCaptions.length; i++) {
            ImageIcon icon;
            icon = createImageIcon(imagedir + imageFileNames[i], imageCaptions[i]);
            ThumbnailAction thumbAction;
            if(icon != null){
                ImageIcon thumbnailIcon = new
                     ImageIcon(getScaledImage(icon.getImage(), 32, 32));
                thumbAction = new ThumbnailAction(icon, thumbnailIcon, imageCaptions[i]);
            } else {
                // the image failed to load for some reason
                // so load a placeholder instead
                thumbAction = new ThumbnailAction(placeholderIcon, placeholderIcon, imageCaptions[i]);
            }
            publish(thumbAction);
        }
        // unfortunately we must return something, and only null is valid to
        // return when the return type is void.
        return null;
    }
    /**
     * Process all loaded images.
     */
    @Override
    protected void process(List<ThumbnailAction> chunks) {
        for (ThumbnailAction thumbAction : chunks) {
            JButton thumbButton = new JButton(thumbAction);
            // add the new button BEFORE the last glue
            // this centers the buttons in the toolbar
            buttonBar.add(thumbButton, buttonBar.getComponentCount() - 1);
        }
    }
};

/**
 * The "missing icon" is a white box with a black border and a red x.
 * It's used to display something when there are issues loading an
 * icon from an external location.
 *
 * @author Collin Fagan
 */
public class MissingIcon implements Icon{
    private int width = 32;
    private int height = 32;
    private BasicStroke stroke = new BasicStroke(4);
    public void paintIcon(Component c, Graphics g, int x, int y) {
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setColor(Color.WHITE);
        g2d.fillRect(x +1 ,y + 1,width -2 ,height -2);
        g2d.setColor(Color.BLACK);
        g2d.drawRect(x +1 ,y + 1,width -2 ,height -2);
        g2d.setColor(Color.RED);
        g2d.setStroke(stroke);
        g2d.drawLine(x +10, y + 10, x + width -10, y + height -10);
        g2d.drawLine(x +10, y + height -10, x + width -10, y + 10);
        g2d.dispose();
    }
    public int getIconWidth() {
        return width;
    }
    public int getIconHeight() {
        return height;
    }
}

private MissingIcon placeholderIcon = new MissingIcon();
...
if(icon != null) {
    ...
} else {
    // the image failed to load for some reason
    // so load a placeholder instead
    thumbAction = new ThumbnailAction(placeholderIcon, placeholderIcon, imageCaptions[i]);
}

JPanel pane = new JPanel();
pane.setBorder(BorderFactory.createLineBorder(Color.black));

//Keep references to the next few borders,
//for use in titles and compound borders.
Border blackline, raisedetched, loweredetched,
       raisedbevel, loweredbevel, empty;
blackline = BorderFactory.createLineBorder(Color.black);
raisedetched = BorderFactory.createEtchedBorder(EtchedBorder.RAISED);
loweredetched = BorderFactory.createEtchedBorder(EtchedBorder.LOWERED);
raisedbevel = BorderFactory.createRaisedBevelBorder();
loweredbevel = BorderFactory.createLoweredBevelBorder();
empty = BorderFactory.createEmptyBorder();
//Simple borders
jComp1.setBorder(blackline);
jComp2.setBorder(raisedbevel);
jComp3.setBorder(loweredbevel);
jComp4.setBorder(empty);
//Matte borders
ImageIcon icon = createImageIcon("images/wavy.gif",
                                 "wavy-line border icon"); //20x22
jComp5.setBorder(BorderFactory.createMatteBorder(
                                   -1, -1, -1, -1, icon));
jComp6.setBorder(BorderFactory.createMatteBorder(
                                    1, 5, 1, 1, Color.red));
jComp7.setBorder(BorderFactory.createMatteBorder(
                                    0, 20, 0, 0, icon));
//Titled borders
TitledBorder title;
title = BorderFactory.createTitledBorder("title");
jComp8.setBorder(title);
title = BorderFactory.createTitledBorder(
                       blackline, "title");
title.setTitleJustification(TitledBorder.CENTER);
jComp9.setBorder(title);
title = BorderFactory.createTitledBorder(
                       loweredetched, "title");
title.setTitleJustification(TitledBorder.RIGHT);
jComp10.setBorder(title);
title = BorderFactory.createTitledBorder(
                       loweredbevel, "title");
title.setTitlePosition(TitledBorder.ABOVE_TOP);
jComp11.setBorder(title);
title = BorderFactory.createTitledBorder(
                       empty, "title");
title.setTitlePosition(TitledBorder.BOTTOM);
jComp12.setBorder(title);
//Compound borders
Border compound;
Border redline = BorderFactory.createLineBorder(Color.red);
//This creates a nice frame.
compound = BorderFactory.createCompoundBorder(
                          raisedbevel, loweredbevel);
jComp13.setBorder(compound);
//Add a red outline to the frame.
compound = BorderFactory.createCompoundBorder(
                          redline, compound);
jComp14.setBorder(compound);
//Add a title to the red-outlined frame.
compound = BorderFactory.createTitledBorder(
                          compound, "title",
                          TitledBorder.CENTER,
                          TitledBorder.BELOW_BOTTOM);
jComp15.setBorder(compound);