Creates and displays a window containing a list of files and sub-directories in a specified directory
/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
import java.awt.Button;
import java.awt.FileDialog;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Frame;
import java.awt.List;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.File;
import java.io.FileReader;
import java.io.FilenameFilter;
import java.io.IOException;
import java.text.DateFormat;
/**
* This class creates and displays a window containing a list of files and
* sub-directories in a specified directory. Clicking on an entry in the list
* displays more information about it. Double-clicking on an entry displays it,
* if a file, or lists it if a directory. An optionally-specified FilenameFilter
* filters the displayed list.
*/
public class FileLister extends Frame implements ActionListener, ItemListener {
private List list; // To display the directory contents in
private TextField details; // To display detail info in.
private Panel buttons; // Holds the buttons
private Button up, close; // The Up and Close buttons
private File currentDir; // The directory currently listed
private FilenameFilter filter; // An optional filter for the directory
private String[] files; // The directory contents
private DateFormat dateFormatter = // To display dates and time correctly
DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT);
/**
* Constructor: create the GUI, and list the initial directory.
*/
public FileLister(String directory, FilenameFilter filter) {
super("File Lister"); // Create the window
this.filter = filter; // Save the filter, if any
// Destroy the window when the user requests it
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
dispose();
}
});
list = new List(12, false); // Set up the list
list.setFont(new Font("MonoSpaced", Font.PLAIN, 14));
list.addActionListener(this);
list.addItemListener(this);
details = new TextField(); // Set up the details area
details.setFont(new Font("MonoSpaced", Font.PLAIN, 12));
details.setEditable(false);
buttons = new Panel(); // Set up the button box
buttons.setLayout(new FlowLayout(FlowLayout.RIGHT, 15, 5));
buttons.setFont(new Font("SansSerif", Font.BOLD, 14));
up = new Button("Up a Directory"); // Set up the two buttons
close = new Button("Close");
up.addActionListener(this);
close.addActionListener(this);
buttons.add(up); // Add buttons to button box
buttons.add(close);
this.add(list, "Center"); // Add stuff to the window
this.add(details, "North");
this.add(buttons, "South");
this.setSize(500, 350);
listDirectory(directory); // And now list initial directory.
}
/**
* This method uses the list() method to get all entries in a directory and
* then displays them in the List component.
*/
public void listDirectory(String directory) {
// Convert the string to a File object, and check that the dir exists
File dir = new File(directory);
if (!dir.isDirectory())
throw new IllegalArgumentException("FileLister: no such directory");
// Get the (filtered) directory entries
files = dir.list(filter);
// Sort the list of filenames.
java.util.Arrays.sort(files);
// Remove any old entries in the list, and add the new ones
list.removeAll();
list.add("[Up to Parent Directory]"); // A special case entry
for (int i = 0; i < files.length; i++)
list.add(files[i]);
// Display directory name in window titlebar and in the details box
this.setTitle(directory);
details.setText(directory);
// Remember this directory for later.
currentDir = dir;
}
/**
* This ItemListener method uses various File methods to obtain information
* about a file or directory. Then it displays that info.
*/
public void itemStateChanged(ItemEvent e) {
int i = list.getSelectedIndex() - 1; // minus 1 for Up To Parent entry
if (i < 0)
return;
String filename = files[i]; // Get the selected entry
File f = new File(currentDir, filename); // Convert to a File
if (!f.exists()) // Confirm that it exists
throw new IllegalArgumentException("FileLister: " + "no such file or directory");
// Get the details about the file or directory, concatenate to a string
String info = filename;
if (f.isDirectory())
info += File.separator;
info += " " + f.length() + " bytes ";
info += dateFormatter.format(new java.util.Date(f.lastModified()));
if (f.canRead())
info += " Read";
if (f.canWrite())
info += " Write";
// And display the details string
details.setText(info);
}
/**
* This ActionListener method is invoked when the user double-clicks on an
* entry or clicks on one of the buttons. If they double-click on a file,
* create a FileViewer to display that file. If they double-click on a
* directory, call the listDirectory() method to display that directory
*/
public void actionPerformed(ActionEvent e) {
if (e.getSource() == close)
this.dispose();
else if (e.getSource() == up) {
up();
} else if (e.getSource() == list) { // Double click on an item
int i = list.getSelectedIndex(); // Check which item
if (i == 0)
up(); // Handle first Up To Parent item
else { // Otherwise, get filename
String name = files[i - 1];
File f = new File(currentDir, name); // Convert to a File
String fullname = f.getAbsolutePath();
if (f.isDirectory())
listDirectory(fullname); // List dir
else
new FileViewer(fullname).show(); // display file
}
}
}
/** A convenience method to display the contents of the parent directory */
protected void up() {
String parent = currentDir.getParent();
if (parent == null)
return;
listDirectory(parent);
}
/** A convenience method used by main() */
public static void usage() {
System.out.println("Usage: java FileLister [directory_name] " + "[-e file_extension]");
System.exit(0);
}
/**
* A main() method so FileLister can be run standalone. Parse command line
* arguments and create the FileLister object. If an extension is specified,
* create a FilenameFilter for it. If no directory is specified, use the
* current directory.
*/
public static void main(String args[]) throws IOException {
FileLister f;
FilenameFilter filter = null; // The filter, if any
String directory = null; // The specified dir, or the current dir
// Loop through args array, parsing arguments
for (int i = 0; i < args.length; i++) {
if (args[i].equals("-e")) {
if (++i >= args.length)
usage();
final String suffix = args[i]; // final for anon. class below
// This class is a simple FilenameFilter. It defines the
// accept() method required to determine whether a specified
// file should be listed. A file will be listed if its name
// ends with the specified extension, or if it is a directory.
filter = new FilenameFilter() {
public boolean accept(File dir, String name) {
if (name.endsWith(suffix))
return true;
else
return (new File(dir, name)).isDirectory();
}
};
} else {
if (directory != null)
usage(); // If already specified, fail.
else
directory = args[i];
}
}
// if no directory specified, use the current directory
if (directory == null)
directory = System.getProperty("user.dir");
// Create the FileLister object, with directory and filter specified.
f = new FileLister(directory, filter);
// Arrange for the application to exit when the window is closed
f.addWindowListener(new WindowAdapter() {
public void windowClosed(WindowEvent e) {
System.exit(0);
}
});
// Finally, pop the window up up.
f.show();
}
}
class FileViewer extends Frame implements ActionListener {
String directory; // The default directory to display in the FileDialog
TextArea textarea; // The area to display the file contents into
/** Convenience constructor: file viewer starts out blank */
public FileViewer() {
this(null, null);
}
/** Convenience constructor: display file from current directory */
public FileViewer(String filename) {
this(null, filename);
}
/**
* The real constructor. Create a FileViewer object to display the specified
* file from the specified directory
*/
public FileViewer(String directory, String filename) {
super(); // Create the frame
// Destroy the window when the user requests it
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
dispose();
}
});
// Create a TextArea to display the contents of the file in
textarea = new TextArea("", 24, 80);
textarea.setFont(new Font("MonoSpaced", Font.PLAIN, 12));
textarea.setEditable(false);
this.add("Center", textarea);
// Create a bottom panel to hold a couple of buttons in
Panel p = new Panel();
p.setLayout(new FlowLayout(FlowLayout.RIGHT, 10, 5));
this.add(p, "South");
// Create the buttons and arrange to handle button clicks
Font font = new Font("SansSerif", Font.BOLD, 14);
Button openfile = new Button("Open File");
Button close = new Button("Close");
openfile.addActionListener(this);
openfile.setActionCommand("open");
openfile.setFont(font);
close.addActionListener(this);
close.setActionCommand("close");
close.setFont(font);
p.add(openfile);
p.add(close);
this.pack();
// Figure out the directory, from filename or current dir, if necessary
if (directory == null) {
File f;
if ((filename != null) && (f = new File(filename)).isAbsolute()) {
directory = f.getParent();
filename = f.getName();
} else
directory = System.getProperty("user.dir");
}
this.directory = directory; // Remember the directory, for FileDialog
setFile(directory, filename); // Now load and display the file
}
/**
* Load and display the specified file from the specified directory
*/
public void setFile(String directory, String filename) {
if ((filename == null) || (filename.length() == 0))
return;
File f;
FileReader in = null;
// Read and display the file contents. Since we're reading text, we
// use a FileReader instead of a FileInputStream.
try {
f = new File(directory, filename); // Create a file object
in = new FileReader(f); // And a char stream to read it
char[] buffer = new char[4096]; // Read 4K characters at a time
int len; // How many chars read each time
textarea.setText(""); // Clear the text area
while ((len = in.read(buffer)) != -1) { // Read a batch of chars
String s = new String(buffer, 0, len); // Convert to a string
textarea.append(s); // And display them
}
this.setTitle("FileViewer: " + filename); // Set the window title
textarea.setCaretPosition(0); // Go to start of file
}
// Display messages if something goes wrong
catch (IOException e) {
textarea.setText(e.getClass().getName() + ": " + e.getMessage());
this.setTitle("FileViewer: " + filename + ": I/O Exception");
}
// Always be sure to close the input stream!
finally {
try {
if (in != null)
in.close();
} catch (IOException e) {
}
}
}
/**
* Handle button clicks
*/
public void actionPerformed(ActionEvent e) {
String cmd = e.getActionCommand();
if (cmd.equals("open")) { // If user clicked "Open" button
// Create a file dialog box to prompt for a new file to display
FileDialog f = new FileDialog(this, "Open File", FileDialog.LOAD);
f.setDirectory(directory); // Set the default directory
// Display the dialog and wait for the user's response
f.show();
directory = f.getDirectory(); // Remember new default directory
setFile(directory, f.getFile()); // Load and display selection
f.dispose(); // Get rid of the dialog box
} else if (cmd.equals("close")) // If user clicked "Close" button
this.dispose(); // then close the window
}
/**
* The FileViewer can be used by other classes, or it can be used standalone
* with this main() method.
*/
static public void main(String[] args) throws IOException {
// Create a FileViewer object
Frame f = new FileViewer((args.length == 1) ? args[0] : null);
// Arrange to exit when the FileViewer window closes
f.addWindowListener(new WindowAdapter() {
public void windowClosed(WindowEvent e) {
System.exit(0);
}
});
// And pop the window up
f.show();
}
}
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