/*
 * Core Java  P407 
 **/

//   本程序是《Java核心技术 卷一：基础知识》（第八版）（中文版 机械工业出版社出版）第407页的源程序
//   我在编译的时候出了错误，但是却找不出来，望高人指点

package first;

import java.awt.*;
import java.awt.event.*;
import java.beans.*;
import java.io.File;
import javax.swing.*;
import javax.swing.filechooser.*;
import javax.swing.filechooser.FileFilter;

/*  这里书上还导入了另一个包：
    import java.util.*;
    但是我在eclipse上编译的时候编译器提示说这个包从来没有用到过
*/

public class FileChooserTest {
    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                ImageViewerFrame frame = new ImageViewerFrame();             //    这里报错
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setTitle("FileChooserTest");
                frame.setVisible(true);
            }
        });
    }
}

/*
 *  A frame that has a menu for loading an image and a display area for the loaded image
 * */
class ImageViewerFrame extends DrawFrame          // 这里的DrawFrame是我自己定义的一个类，主要是设置Frame
                                                  // 的宽和高
{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    private JLabel label ;
    private JFileChooser chooser ;
    
    public ImageViewerFrame()
    {
        // set a menu bar
        JMenuBar mBar = new JMenuBar();
        setJMenuBar(mBar);
        
        JMenu menu = new JMenu("File");
        mBar.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 image 
        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");
        */
        FileNameExtensionFilter filter = new FileNameExtensionFilter("Image files", "jpg", "jpeg", "gif");
        chooser.setFileFilter(filter);
        chooser.setAccessory(new ImagePreviewer(chooser));      //这里报错
        chooser.setFileView(new FileIconView(filter, new ImageIcon("palette.gif")));
    }
    
    private class FileOpenListener implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
            chooser.setCurrentDirectory(new File("."));
            
            // shoe 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));
            }
        }
    }
}

/*
 * A file view that display an icon for all files that match a file filter 
 * */
class FileIconView extends FileView
{
    private FileFilter filter ;
    private Icon icon ;
    
    // constructs a FileIconView
    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;
    }
}

/*
 *  A file chooser accessory that previews images
 * */
class ImagePreviewer extends JLabel
{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    // constructs an ImagePreviewer
    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();      //这里报错
                    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);
                }
            }
        });
    }
}