Пожалуйста, найдите пример кода для загрузки файлов jpg в jframe с иконками предварительного просмотра.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.net.MalformedURLException;
import java.util.List;
import javax.swing.AbstractAction;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class IconicImage2 extends JFrame {
private JLabel photographLabel = new JLabel();
private JToolBar buttonBar = new JToolBar();
private String imagedir = "images/icons/";
/**
* List of all the descriptions of the image files. These correspond one to one
* with the image file names
*/
private String[] imageCaptions = { "Original SUNW Logo", "The Clocktower", "Clocktower from the West",
"The Mansion", "Sun Auditorium" };
/**
* List of all the image files to load.
*/
private String[] imageFileNames = { "1.jpg", "2.jpg", "3.jpg", "4.jpg" };
/**
* Main entry point to the demo. Loads the Swing elements on the "Event Dispatch
* Thread".
*
* @param args
*/
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
IconicImage2 app = new IconicImage2();
app.setSize(new Dimension(800, 600));
app.setVisible(true);
}
});
}
/**
* Default constructor for the demo.
*/
public IconicImage2() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Icon Demo: Please Select an Image");
// A label for displaying the pictures
photographLabel.setVerticalTextPosition(JLabel.BOTTOM);
photographLabel.setHorizontalTextPosition(JLabel.CENTER);
photographLabel.setHorizontalAlignment(JLabel.CENTER);
photographLabel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
JScrollPane scrollPane = new JScrollPane(photographLabel);
setPreferredSize(new Dimension(450, 110));
// We add two glue components. Later in process() we will add thumbnail buttons
// to the toolbar inbetween thease glue compoents. This will center the
// buttons in the toolbar.
buttonBar.add(Box.createGlue());
buttonBar.add(Box.createGlue());
add(buttonBar, BorderLayout.SOUTH);
add(scrollPane, BorderLayout.CENTER);
setSize(400, 300);
// this centers the frame on the screen
setLocationRelativeTo(null);
// start the image loading SwingWorker in a background thread
loadimages.execute();
}
/**
* 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 SwingWroker 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 = null;
if (icon != null) {
ImageIcon thumbnailIcon = new ImageIcon(getScaledImage(icon.getImage(), 32, 32));
thumbAction = new ThumbnailAction(icon, thumbnailIcon, imageCaptions[i]);
}
if (thumbAction != null)
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);
}
}
};
/**
* Creates an ImageIcon if the path is valid.
*
* @param String
* - resource path
* @param String
* - description of the file
* @throws MalformedURLException
*/
protected ImageIcon createImageIcon(String path, String description) throws MalformedURLException {
// java.net.URL imgURL = new java.net.URL(path);
if (path != null) {
return new ImageIcon(path, description);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}
/**
* Resizes an image using a Graphics2D object backed by a BufferedImage.
*
* @param srcImg
* - source image to scale
* @param w
* - desired width
* @param h
* - desired height
* @return - the new resized image
*/
private Image getScaledImage(Image srcImg, int w, int h) {
BufferedImage resizedImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = resizedImg.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2.drawImage(srcImg, 0, 0, w, h, null);
g2.dispose();
return resizedImg;
}
/**
* Action class that shows the image specified in it's constructor.
*/
private class ThumbnailAction extends AbstractAction {
/**
* The icon if the full image we want to display.
*/
private Icon displayPhoto;
/**
* @param Icon
* - The full size photo to show in the button.
* @param Icon
* - The thumbnail to show in the button.
* @param String
* - The descriptioon of the icon.
*/
public ThumbnailAction(Icon photo, Icon thumb, String desc) {
displayPhoto = photo;
// The short description becomes the tooltip of a button.
putValue(SHORT_DESCRIPTION, desc);
// The LARGE_ICON_KEY is the key for setting the
// icon when an Action is applied to a button.
putValue(LARGE_ICON_KEY, thumb);
}
/**
* Shows the full image in the main area and sets the application title.
*/
public void actionPerformed(ActionEvent e) {
photographLabel.setIcon(displayPhoto);
setTitle("Icon Demo: " + getValue(SHORT_DESCRIPTION).toString());
}
}
}
Ссылка
Пожалуйста, перейдите по следующей ссылке, которая показывает эскизЗначок программы с примером.
https://docs.oracle.com/javase/tutorial/uiswing/components/icon.html
- Перейти к разделу «Пример более сложного изображения»
- См. программу «IconDemoApp.java»
- Или Нажмите кнопку запуска jnlp, чтобы увидеть демонстрацию.