Αντικειμενοστραφής Προγραμματισμός

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====== File Browser ======

Παραθέτουμε ένα παράδειγμα εφαρμογής swing (παρουσιάστηκε στην τάξη στις 30/5 και 1/6) που υλοποιεί ένα file browser για τον υπολογιστή σας με την βοήθεια ενός [[https://docs.oracle.com/javase/7/docs/api/javax/swing/JList.html|javax.swing.JList]]. Δείτε την υλοποίηση του κώδικα παρακάτω και κατεβάστε το πακέτο έτοιμο προς μεταγλώττιση και εκτέλεση από {{:swing:filebrowser.zip|εδώ}}. 

<code java FileBrowser.java>
package ce325.swing;

import java.io.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;

public class FileBrowser extends JPanel {

  JTextField text;
  JButton nextBtn, backBtn, upBtn, homeBtn;
  JList<File> list;
  ArrayList<File> history;
  boolean showHiddenFiles = true;
  
  public FileBrowser() {
    setLayout( new BorderLayout() );
    JPanel north = new JPanel();
    add(north, BorderLayout.NORTH);
    
    backBtn = new JButton(new ImageIcon("images/back.png"));
    backBtn.setActionCommand("back");
    BackBtnListener backBtnListener = new BackBtnListener();
    backBtn.addActionListener( backBtnListener );
    backBtn.setMargin( new Insets(0,0,0,0) );
    
    upBtn = new JButton(new ImageIcon("images/up.png"));
    upBtn.setActionCommand("up");
    UpBtnListener upBtnListener = new UpBtnListener();
    upBtn.addActionListener( upBtnListener );
    upBtn.setMargin( new Insets(0,0,0,0) );
    
    homeBtn = new JButton(new ImageIcon("images/home.png"));
    homeBtn.addActionListener( new HomeBtnListener() );
    homeBtn.setMargin(new Insets(0,0,0,0));
    
    nextBtn = new JButton(new ImageIcon("images/next.png"));
    nextBtn.setActionCommand("next");
    NextBtnListener nextBtnListener = new NextBtnListener();
    nextBtn.addActionListener( nextBtnListener );
    nextBtn.setMargin( new Insets(0,0,0,0) );
    
    history = new ArrayList<>();
    history.add( new File(System.getProperty("user.home")) );
    
    text = new JTextField( System.getProperty("user.home"), 40);
    text.addActionListener( nextBtnListener );
    text.setFont( new Font("Default", Font.BOLD, 18) );
    
    north.setLayout( new FlowLayout(FlowLayout.LEFT) );
    north.add(backBtn);
    north.add(upBtn);
    north.add(homeBtn);
    north.add(text);
    north.add(nextBtn);
    
    list = new JList<File>( listFiles(System.getProperty("user.home")) );
    list.setVisibleRowCount(20);
    list.addMouseListener( new ListMouseListener() );
    MyCellRenderer renderer = new MyCellRenderer();
    list.setCellRenderer( renderer );
    JScrollPane scrollpane = new JScrollPane(list);
    add(scrollpane, BorderLayout.SOUTH);    
  }
  
  JMenuBar createMenu() {
    JMenuBar menubar = new JMenuBar();
    JMenu file = new JMenu("File");
    JMenu options = new JMenu("Options");
    menubar.add(file);
    menubar.add(options);
    JMenuItem newBrowser = new JMenuItem("New..");
    file.add(newBrowser);
    final JCheckBoxMenuItem showHidden = new JCheckBoxMenuItem("Show hidden files/folders", showHiddenFiles);
    showHidden.addActionListener( new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        showHiddenFiles = showHidden.getState();
        updateListFromCurrentDir();
      }
    });
    options.add(showHidden);
    return menubar;
  }
  
  File[] listFiles(String path) {
    File file = new File(path);
    return listFiles(file);
  }
  
  File[] listFiles(File file) {
    if( file == null || !file.exists() )
      return null;
      
    File [] files = file.listFiles();
    if( !showHiddenFiles ) {
      ArrayList<File> listedFiles = new ArrayList<>();
      for(File f : files) {
        if( f==null || f.isHidden() ) 
          continue;
        listedFiles.add(f);
      }
      files = new File[listedFiles.size()];
      for(int i=0; i<listedFiles.size(); i++) {
        files[i] = listedFiles.get(i);
      }
    }
    java.util.Arrays.sort( files, new Comparator<File>() {
      public int compare(File f1, File f2) {
        if( f1.isDirectory() && f2.isDirectory() ) 
          return f1.compareTo(f2);
        if( !f1.isDirectory() && f2.isDirectory() ) 
          return 1;
        if( f1.isDirectory() && !f2.isDirectory() ) 
          return -1;
        if( !f1.isDirectory() && !f2.isDirectory() )
          return f1.compareTo(f2);
        return 0;
      }
    });
    return files; 
  }
  
  void updateListFromText(String text) {
    File f = new File(text);
    File lastInHistory = history.get( history.size()-1);
    if( f.exists() && f.isDirectory() && !f.getAbsolutePath().equals(lastInHistory.getAbsolutePath()) ) {
      history.add(f);
    }
    File[] dirContents = listFiles(f);
    if( dirContents == null )  {
      JOptionPane.showMessageDialog( FileBrowser.this, "The selected path: \""+ text +"\" is invalid!", "Invalid Path", JOptionPane.ERROR_MESSAGE ); 
      return;
    }        
    list.setListData(dirContents);
  }
  
  void updateListFromCurrentDir() {
    File lastInHistory = history.get( history.size()-1);
    File[] dirContents = listFiles(lastInHistory);
    list.setListData(dirContents);
  }
  
  class NextBtnListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      updateListFromText(text.getText());
    }
  }
  
  class BackBtnListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      if( history.size() < 2 )
        return;
      history.remove( history.size() -1 );
      File f = history.get( history.size() -1 );
      File[] dirContents = listFiles(f);
      text.setText(f.getAbsolutePath());
      list.setListData(dirContents);
    }
  }
  
  class UpBtnListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      File f = history.get(history.size()-1);
      File parent = f.getParentFile();
      if( parent==null || !parent.exists() )
        return;
      history.add(parent);
      text.setText( parent.getAbsolutePath() );
      File []dirContents = listFiles(parent);
      list.setListData(dirContents);
    }
  }
  
  class HomeBtnListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      String updatedText = System.getProperty("user.home");
      File[] updatedFiles = listFiles(updatedText);
      
      history.add( new File(updatedText) );
      text.setText(updatedText);
      list.setListData(updatedFiles);
    }
  }
  
  class ListMouseListener extends MouseAdapter {
    public void mouseClicked(MouseEvent e) {
      if( e.getButton() == MouseEvent.BUTTON1 && e.getClickCount() == 2) {
        int index = list.locationToIndex(e.getPoint());
        File f = list.getModel().getElementAt(index);
        if( f.isDirectory() ) {
          File[] dirContents = listFiles(f);
          text.setText(f.getAbsolutePath());
          list.setListData(dirContents);
          history.add(f);
        }
        else {
          try {
            Desktop.getDesktop().open( f );
          }
          catch(IOException ex) {
            JOptionPane.showMessageDialog( FileBrowser.this, "Unable to open file: \""+ f.getName() +"\"!", "Error opening file", JOptionPane.ERROR_MESSAGE ); 
            return;
          }
        }
      }
    }
  }
  
  class MyCellRenderer implements ListCellRenderer<Object> {
     public MyCellRenderer() {
     }

     public Component getListCellRendererComponent(JList<?> list,
                                                   Object value,
                                                   int index,
                                                   boolean isSelected,
                                                   boolean cellHasFocus) {
       ImageIcon icon;
       File f = (File)value;
       if( f.isDirectory() ) {
         icon = new ImageIcon("images/dir.png");         
       }
       else {
         icon = new ImageIcon("images/file.png");
       }
       Image image = icon.getImage().getScaledInstance(25, 25, Image.SCALE_DEFAULT);
       icon = new ImageIcon(image);
       JLabel label = new JLabel(f.getName(), icon, JLabel.LEFT );
       label.setOpaque(true);
       return label;
     }
   }
  
  public static void main(String []args) {
    JFrame myFrame = new JFrame("CE325 File Browser");
    FileBrowser browser = new FileBrowser();
    
    myFrame.setJMenuBar( browser.createMenu() );
    myFrame.setContentPane(browser);
    myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
    myFrame.setVisible(true);
    myFrame.pack();
  }
}
</code>