用Java怎么实现？
我想用Java做一个文件夹对话框，弹出该对话框后只能显示所选目录下的文件夹，选中某个文件夹，可以自动获取这个文件夹下所有文件（.txt）进行其他处理。请问应该怎么做？用什么类？
[解决办法]
JFileChooser
在jdk帮助中的例子如下:
JFileChooser chooser = new JFileChooser();
// Note: source for ExampleFileFilter can be found in FileChooserDemo,
// under the demo/jfc directory in the Java 2 SDK, Standard Edition.
ExampleFileFilter filter = new ExampleFileFilter();
filter.addExtension( "jpg ");
filter.addExtension( "gif ");
filter.setDescription( "JPG & GIF Images ");
chooser.setFileFilter(filter);
int returnVal = chooser.showOpenDialog(parent);
if(returnVal == JFileChooser.APPROVE_OPTION) {
System.out.println( "You chose to open this file: " +
chooser.getSelectedFile().getName());
}
[解决办法]
楼上正解
[解决办法]
给楼主一个程序和你的要求一样。
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();
label.setHorizontalAlignment(SwingConstants.CENTER);
label.setVerticalAlignment(SwingConstants.CENTER);
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.setDescription( "JPG格式图片 ");
filter.addExtension( "jpeg ");
filter.addExtension( "gif ");
filter.setDescription( "Image files ");
filter.setDescription( "JPG格式图片 ");
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);
}
}
});
}
}
[解决办法]
package com.xxx;
import java.io.File;
import javax.swing.filechooser.*;
/* ImageFilter.java is used by FileChooserDemo2.java. */
public class TextFilter extends FileFilter {
/*
* Get the extension of a file.
*/
public static String getExtension(File f) {
String ext = null;
String s = f.getName();
int i = s.lastIndexOf( '. ');
if (i > 0 && i < s.length() - 1) {
ext = s.substring(i+1).toLowerCase();
}
return ext;
}
//Accept all directories and all gif, jpg, tiff, or png files.
public boolean accept(File f) {
if (f.isDirectory()) {
return true;
}
String extension = getExtension(f);
if (extension != null) {
if (extension.equals( "txt ") ||
extension.equals( "dat ")) {
return true;
} else {
return false;
}
}
return false;
}
//The description of this filter
public String getDescription() {
return "Just Text Files ";
}
}