Java: Example - Simple Editor
This very simple editor illustrates several things: the use of menus, JFileChooser, and Actions.
Actions. This simple text editor uses a JTextArea with Actions to
implement the menu items. Actions are a good way to implement ActionListeners.
- Actions can be used with most buttons, including toolbox buttons and menu items, text fields, etc.
- They can be shared so that all components which do the same thing can share an Action.
- Actions can be dis-/enabled, and they will then dis-/enable all corresponding controls.
- They can be used to set icons, tooltip text, accelerator and mnemonic keys.
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// File : editor/NutPad.java -- A very simple text editor
// Purpose: Illustrates use of AbstractActions for menus.
// It only uses a few Action features. Many more are available.
// This program uses the obscure "read" and "write"
// text component methods.
// Author : Fred Swartz - 2006-12-14 - Placed in public domain.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
///////////////////////////////////////////////////////////////////////// NutPad
public class NutPad extends JFrame {
//... Components
private JTextArea _editArea;
private JFileChooser _fileChooser = new JFileChooser();
//... Create actions for menu items, buttons, ...
private Action _openAction = new OpenAction();
private Action _saveAction = new SaveAction();
private Action _exitAction = new ExitAction();
//===================================================================== main
public static void main(String[] args) {
new NutPad();
}
//============================================================== constructor
public NutPad() {
//... Create scrollable text area.
_editArea = new JTextArea(15, 80);
_editArea.setBorder(BorderFactory.createEmptyBorder(2,2,2,2));
_editArea.setFont(new Font("monospaced", Font.PLAIN, 14));
JScrollPane scrollingText = new JScrollPane(_editArea);
//-- Create a content pane, set layout, add component.
JPanel content = new JPanel();
content.setLayout(new BorderLayout());
content.add(scrollingText, BorderLayout.CENTER);
//... Create menubar
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = menuBar.add(new JMenu("File"));
fileMenu.setMnemonic('F');
fileMenu.add(_openAction); // Note use of actions, not text.
fileMenu.add(_saveAction);
fileMenu.addSeparator();
fileMenu.add(_exitAction);
//... Set window content and menu.
setContentPane(content);
setJMenuBar(menuBar);
//... Set other window characteristics.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("NutPad");
pack();
setLocationRelativeTo(null);
setVisible(true);
}
////////////////////////////////////////////////// inner class OpenAction
class OpenAction extends AbstractAction {
//============================================= constructor
public OpenAction() {
super("Open...");
putValue(MNEMONIC_KEY, new Integer('O'));
}
//========================================= actionPerformed
public void actionPerformed(ActionEvent e) {
int retval = _fileChooser.showOpenDialog(NutPad.this);
if (retval == JFileChooser.APPROVE_OPTION) {
File f = _fileChooser.getSelectedFile();
try {
FileReader reader = new FileReader(f);
_editArea.read(reader, ""); // Use TextComponent read
} catch (IOException ioex) {
System.out.println(e);
System.exit(1);
}
}
}
}
//////////////////////////////////////////////////// inner class SaveAction
class SaveAction extends AbstractAction {
//============================================= constructor
SaveAction() {
super("Save...");
putValue(MNEMONIC_KEY, new Integer('S'));
}
//========================================= actionPerformed
public void actionPerformed(ActionEvent e) {
int retval = _fileChooser.showSaveDialog(NutPad.this);
if (retval == JFileChooser.APPROVE_OPTION) {
File f = _fileChooser.getSelectedFile();
try {
FileWriter writer = new FileWriter(f);
_editArea.write(writer); // Use TextComponent write
} catch (IOException ioex) {
JOptionPane.showMessageDialog(NutPad.this, ioex);
System.exit(1);
}
}
}
}
///////////////////////////////////////////////////// inner class ExitAction
class ExitAction extends AbstractAction {
//============================================= constructor
public ExitAction() {
super("Exit");
putValue(MNEMONIC_KEY, new Integer('X'));
}
//========================================= actionPerformed
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
}
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