// This example is from _Java Examples in a Nutshell_. (http://www.oreilly.com)
// Copyright (c) 1997 by David Flanagan
// This example is provided WITHOUT ANY WARRANTY either expressed or implied.
// You may study, use, modify, and distribute it for non-commercial purposes.
// For any commercial use, see http://www.davidflanagan.com/javaexamples
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
/** An applet with a popup menu or an application with pulldown menus */
public class MenuScribble extends Applet implements ActionListener {
/**
* The main() method. If this program is invoked as an application, this
* method will create a window and pulldown menu system for it.
*/
public static void main(String[] args) {
Frame f = new Frame(); // Create a window
MenuScribble applet = new MenuScribble(); // Create the applet panel
f.add(applet, "Center"); // Add applet to window
applet.init(); // Initialize the applet
// Create a menubar and tell the frame about it
MenuBar menubar = new MenuBar();
f.setMenuBar(menubar);
// Create three pulldown menus for the menubar
Menu file = new Menu("File");
Menu colors = new Menu("Colors");
Menu help = new Menu("Help");
// Add the menus to the bar, and treat Help menu specially.
menubar.add(file);
menubar.add(colors);
menubar.add(help);
menubar.setHelpMenu(help);
// Add two items, with a keyboard shortcuts to the File menu
MenuItem clear = new MenuItem("Clear", new MenuShortcut(KeyEvent.VK_C));
clear.addActionListener(applet); // Say who's listening for the events
clear.setActionCommand("clear"); // A detail to go along with the events
file.add(clear); // Add item to menu pane
MenuItem quit = new MenuItem("Quit", new MenuShortcut(KeyEvent.VK_Q));
quit.addActionListener(applet);
quit.setActionCommand("quit");
file.add(quit);
// Add items to the other two menus, this time using a convenience
// method defined below. Note use of new anonymous array syntax.
createMenuItems(colors, applet,
new String[] { "Red", "Green", "Blue", "Black" },
new String[] { "red", "green", "blue", "black" },
new int[] { KeyEvent.VK_R, KeyEvent.VK_G,
KeyEvent.VK_B, KeyEvent.VK_L });
createMenuItems(help, applet,
new String[] { "About" }, new String[] {"about"},
new int[] { KeyEvent.VK_A });
// Handle window close requests
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) { System.exit(0); }
});
f.setSize(400, 400); // Set the size of the window
f.show(); // Finally, pop the window up.
}
/**
* The init() method. If the program is invoked as an applet, the browser
* allocates screen space for it and calls this method to set things up.
* If running as an applet, this method creates a popup menu and adds
* it to the applet.
*/
public void init() {
// If we are not in a frame (i.e. we are an applet), create a popup menu
if (!(this.getParent() instanceof Frame)) {
// Create the popup menu
popup = new PopupMenu("File");
// Add items to it using the convenience routine below
createMenuItems(popup, this,
new String[] {"Clear", "Red", "Green", "Blue", "Black"},
new String[] {"clear", "red", "green", "blue", "black"},
new int[] { KeyEvent.VK_C, KeyEvent.VK_R, KeyEvent.VK_G,
KeyEvent.VK_B, KeyEvent.VK_L });
// Add the popup menu to the component it will appear over.
this.add(popup);
}
// Define, instantiate and register the Listener objects for scribbling
this.addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
lastx = e.getX(); lasty = e.getY();
}
});
this.addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
Graphics g = getGraphics();
int x = e.getX(), y = e.getY();
g.setColor(color); // draw with the specified color
g.drawLine(lastx, lasty, x, y);
lastx = x; lasty = y;
}
});
}
/**
* This is the convenience routine for adding menu items to a menu pane.
* It works for pulldown or popup menu panes, since PopupMenu extends Menu.
*/
protected static void createMenuItems(Menu pane, ActionListener listener,
String[] labels, String[] commands,
int[] shortcuts) {
for(int i = 0; i < labels.length; i++) {
MenuItem mi = new MenuItem(labels[i]);
mi.addActionListener(listener);
if ((commands != null) && (commands[i] != null))
mi.setActionCommand(commands[i]);
if ((shortcuts != null) && (shortcuts[i] != 0))
mi.setShortcut(new MenuShortcut(shortcuts[i]));
pane.add(mi);
}
}
/**
* This method is required to make the popup menu, if any, pop up. It
* uses the low-level Java 1.1 event handling mechanism to test all mouse
* events (except mouse motion events) to see if they are the platform-
* dependent popup menu trigger. If so, it calls show() to pop the
* popup up. If not, it passes the event to the superclass version of
* this method so that it is dispatched as usual and can be passed to
* the listener object registered by the init method for scribbling.
*/
public void processMouseEvent(MouseEvent e) {
if ((popup != null) && e.isPopupTrigger())
popup.show(this, e.getX(), e.getY());
else super.processMouseEvent(e);
}
/**
* This is the method defined by the ActionListener interface. All
* the menu item commands are handled here because the applet was specified
* as the listener for all menu items. Note the use of getActionCommand()
* to determine the command string registered with the individual items.
*/
public void actionPerformed(ActionEvent e) {
String cmd = e.getActionCommand();
if (cmd.equals("quit")) System.exit(0); // Don't do this in an applet
else if (cmd.equals("clear")) clear(); // defined below
else if (cmd.equals("about")) /* not yet implemented */ ;
else if (cmd.equals("red")) color = Color.red;
else if (cmd.equals("green")) color = Color.green;
else if (cmd.equals("blue")) color = Color.blue;
else if (cmd.equals("black")) color = color.black;
}
/** Clear the applet area. Used by actionPerformed() above */
protected void clear() {
Graphics g = this.getGraphics();
g.setColor(this.getBackground());
g.fillRect(0, 0, this.getSize().width, this.getSize().height);
}
// Here are the instance variables for this program
protected int lastx, lasty; // Coordinates of last mouse click
protected Color color = Color.black; // Current drawing color
protected PopupMenu popup;
}
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