FileListerpublic class FileLister extends Frame implements ActionListener, ItemListener| 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. |
| Fields Summary |
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| private List | list | | private TextField | details | | private Panel | buttons | | private Button | up | | private Button | close | | private File | currentDir | | private FilenameFilter | filter | | private String[] | files | | private DateFormat | dateFormatter |
| Constructors Summary |
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public FileLister(String directory, FilenameFilter filter)Constructor: create the GUI, and list the initial directory.
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.
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| Methods Summary |
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| public void | actionPerformed(java.awt.event.ActionEvent e)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
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
}
}
| | public void | itemStateChanged(java.awt.event.ItemEvent e)This ItemListener method uses various File methods to obtain information
about a file or directory. Then it displays that info.
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);
| | public void | listDirectory(java.lang.String directory)This method uses the list() method to get all entries in a directory
and then displays them in the List component.
// 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;
| | public static void | main(java.lang.String[] args)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.
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();
| | protected void | up()A convenience method to display the contents of the parent directory
String parent = currentDir.getParent();
if (parent == null) return;
listDirectory(parent);
| | public static void | usage()A convenience method used by main()
System.out.println("Usage: java FileLister [directory_name] " +
"[-e file_extension]");
System.exit(0);
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