filechoosertest.java

该压缩包里面包含了

/**
   @version 1.22 2004-05-06
   @author Cay Horstmann
*/

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.beans.*;
import java.util.*;
import java.io.*;
import javax.swing.*;
import javax.swing.filechooser.FileFilter;
import javax.swing.filechooser.FileView;

public class FileChooserTest
{
   public static void main(String[] args)
   {
      ImageViewerFrame frame = new ImageViewerFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

/**
   A frame that has a menu for loading an image and a display
   area for the loaded image.
*/
class ImageViewerFrame extends JFrame
{
   public ImageViewerFrame()
   {
      setTitle("FileChooserTest");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      // set up menu bar
      JMenuBar menuBar = new JMenuBar();
      setJMenuBar(menuBar);

      JMenu menu = new JMenu("File");
      menuBar.add(menu);

      JMenuItem openItem = new JMenuItem("Open");
      menu.add(openItem);
      openItem.addActionListener(new FileOpenListener());

      JMenuItem exitItem = new JMenuItem("Exit");
      menu.add(exitItem);
      exitItem.addActionListener(new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               System.exit(0);
            }
         });

      // use a label to display the images
      label = new JLabel();
      add(label);

      // set up file chooser
      chooser = new JFileChooser();

      // accept all image files ending with .jpg, .jpeg, .gif
      final ExtensionFileFilter filter = new ExtensionFileFilter();
      filter.addExtension("jpg");
      filter.addExtension("jpeg");
      filter.addExtension("gif");
      filter.setDescription("Image files");
      chooser.setFileFilter(filter);

      chooser.setAccessory(new ImagePreviewer(chooser));
      
      chooser.setFileView(new FileIconView(filter, new ImageIcon("palette.gif")));
   }
   
   /**
      This is the listener for the File->Open menu item.
   */
   private class FileOpenListener implements ActionListener
   {
      public void actionPerformed(ActionEvent event)
      {
         chooser.setCurrentDirectory(new File("."));

         // show file chooser dialog
         int result = chooser.showOpenDialog(ImageViewerFrame.this);

         // if image file accepted, set it as icon of the label
         if(result == JFileChooser.APPROVE_OPTION)
         {
            String name = chooser.getSelectedFile().getPath();
            label.setIcon(new ImageIcon(name));
         }
      }
   }

   public static final int DEFAULT_WIDTH = 300;
   public static final int DEFAULT_HEIGHT = 400;  

   private JLabel label;
   private JFileChooser chooser;
}

/**
   This file filter matches all files with a given set of 
   extensions.
*/
class ExtensionFileFilter extends FileFilter
{
   /**
      Adds an extension that this file filter recognizes.
      @param extension a file extension (such as ".txt" or "txt")
   */
   public void addExtension(String extension)
   {
      if (!extension.startsWith("."))
         extension = "." + extension;
      extensions.add(extension.toLowerCase());     
   }

   /**
      Sets a description for the file set that this file filter
      recognizes.
      @param aDescription a description for the file set
   */
   public void setDescription(String aDescription)
   {
      description = aDescription;
   }

   /**
      Returns a description for the file set that this file
      filter recognizes.
      @return a description for the file set
   */
   public String getDescription()
   {
      return description; 
   }

   public boolean accept(File f)
   {
      if (f.isDirectory()) return true;
      String name = f.getName().toLowerCase();

      // check if the file name ends with any of the extensions
      for (String extension : extensions)
         if (name.endsWith(extension)) 
            return true;
      return false;
   }
   
   private String description = "";
   private ArrayList<String> extensions = new ArrayList<String>();
}

/**
   A file view that displays an icon for all files that match
   a file filter.
*/
class FileIconView extends FileView
{
   /** 
       Constructs a FileIconView.
       @param aFilter a file filter--all files that this filter
       accepts will be shown with the icon.
       @param anIcon--the icon shown with all accepted files.
   */
   public FileIconView(FileFilter aFilter, Icon anIcon)
   {
      filter = aFilter;
      icon = anIcon;
   }

   public Icon getIcon(File f)
   {
      if (!f.isDirectory() && filter.accept(f)) 
         return icon;
      else return null;
   }
   
   private FileFilter filter;
   private Icon icon;
}

/**
   A file chooser accessory that previews images.
*/
class ImagePreviewer extends JLabel 
{
   /**
      Constructs an ImagePreviewer.
      @param chooser the file chooser whose property changes
      trigger an image change in this previewer
   */
   public ImagePreviewer(JFileChooser chooser) 
   {
      setPreferredSize(new Dimension(100, 100));
      setBorder(BorderFactory.createEtchedBorder());

      chooser.addPropertyChangeListener(new 
         PropertyChangeListener()
         {
            public void propertyChange(PropertyChangeEvent 
               event) 
            {
               if (event.getPropertyName() ==
                  JFileChooser.SELECTED_FILE_CHANGED_PROPERTY)
               {
                  // the user has selected a new file 
                  File f = (File) event.getNewValue();
                  if (f == null) { setIcon(null); return; }
                  
                  // read the image into an icon
                  ImageIcon icon = new ImageIcon(f.getPath());

                  // if the icon is too large to fit, scale it
                  if(icon.getIconWidth() > getWidth())
                     icon = new ImageIcon(icon.getImage().getScaledInstance(
                        getWidth(), -1, Image.SCALE_DEFAULT));

                  setIcon(icon);
               }
	    }
         });
   }
}