Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions

  




 

 

Thinking in Java
Prev Contents / Index Next

File dialogs

Some operating systems have a number of special built-in dialog boxes to handle the selection of things such as fonts, colors, printers, and the like. Virtually all graphical operating systems support the opening and saving of files, so Java’s JFileChooser encapsulates these for easy use.

The following application exercises two forms of JFileChooser dialogs, one for opening and one for saving. Most of the code should by now be familiar, and all the interesting activities happen in the action listeners for the two different button clicks:

//: c14:FileChooserTest.java
// Demonstration of File dialog boxes.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import com.bruceeckel.swing.*;

public class FileChooserTest extends JFrame {
  private JTextField
    filename = new JTextField(),
    dir = new JTextField();
  private JButton
    open = new JButton("Open"),
    save = new JButton("Save");
  public FileChooserTest() {
    JPanel p = new JPanel();
    open.addActionListener(new OpenL());
    p.add(open);
    save.addActionListener(new SaveL());
    p.add(save);
    Container cp = getContentPane();
    cp.add(p, BorderLayout.SOUTH);
    dir.setEditable(false);
    filename.setEditable(false);
    p = new JPanel();
    p.setLayout(new GridLayout(2,1));
    p.add(filename);
    p.add(dir);
    cp.add(p, BorderLayout.NORTH);
  }
  class OpenL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      JFileChooser c = new JFileChooser();
      // Demonstrate "Open" dialog:
      int rVal = c.showOpenDialog(FileChooserTest.this);
      if(rVal == JFileChooser.APPROVE_OPTION) {
        filename.setText(c.getSelectedFile().getName());
        dir.setText(c.getCurrentDirectory().toString());
      }
      if(rVal == JFileChooser.CANCEL_OPTION) {
        filename.setText("You pressed cancel");
        dir.setText("");
      }
    }
  }
  class SaveL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      JFileChooser c = new JFileChooser();
      // Demonstrate "Save" dialog:
      int rVal = c.showSaveDialog(FileChooserTest.this);
      if(rVal == JFileChooser.APPROVE_OPTION) {
        filename.setText(c.getSelectedFile().getName());
        dir.setText(c.getCurrentDirectory().toString());
      }
      if(rVal == JFileChooser.CANCEL_OPTION) {
        filename.setText("You pressed cancel");
        dir.setText("");
      }
    }
  }
  public static void main(String[] args) {
    Console.run(new FileChooserTest(), 250, 110);
  }
} ///:~


Note that there are many variations you can apply to JFileChooser, including filters to narrow the file names that you will allow.

For an “open file” dialog, you call showOpenDialog( ), and for a “save file” dialog, you call showSaveDialog( ). These commands don’t return until the dialog is closed. The JFileChooser object still exists, so you can read data from it. The methods getSelectedFile( ) and getCurrentDirectory( ) are two ways you can interrogate the results of the operation. If these return null, it means the user canceled out of the dialog.
Thinking in Java
Prev Contents / Index Next


 
 
   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire