ITEEDU

12-4:使用JCheckBoxMenuItem:

JCheckBoxMenuItem的类层次结构图:

   java.lang.Object
   --java.awt.Component
    --java.awt.Container
     --javax.swing.JComponent
      --javax.swing.AbstractButton
       --javax.swing.JMenuItem
         --javax.swing.JCheckBoxMenuItem

JCheckBoxMenuItem继承JMenuItem类,因此JCheckBoxMenuItem可以使用JMenuItem所提供的方法,而且JCheckBoxMenuItem也具有 AbstractButton的特性,而JChcekBoxMenuItem和JCheckBox的性质几乎是一样,两者间最大的差别在于JCheckBoxMenuItem是专用在 MenuItem上.我们来看看JCheckBoxMenuItem的构造方法:

JCheckBoxMenuItem构造函数:

• JCheckBoxMenuItem():建立一个新的JCheckBoxMenuItem.
• JCheckBoxMenuItem(Action a):建立一个支持Action的新的JCheckBoxMenuItem.
• JCheckBoxMenuItem(Icon icon):建立一个有图标的JCheckBoxMenuItem.
• JCheckBoxMenuItem(String text):建立一个有文字的JCheckBoxMenuItem.
• JCheckBoxMenuItem(String text,Boolean b):建立一个有文字和设置选择状态的JCheckBoxMenuItem.
• JCheckBoxMenuItem(String text,Icon icon):建立一个有文字和图标的JCheckBoxMenuItem.
• JCheckBoxMenuItem(String text,Icon icon,Boolean b):建立一个有文字,图标和设置状态的JCheckBoxMenuItem.

12-4-1:构造JCheckBoxMenuItem组件:

由上表可以看出JCheckBoxMenuItem的构造方式与JMenuItem的构造方式几乎一模一样,唯一有差异的是JCheckBoxMenuItem的构 造方式中多了设置选择状况的构造方式,设置选择状态就是决定是否要将构造好的JCheckBoxMenuItem组件设置成默认值.我们来看下 面的范例:

JCheckBoxMenuItem1.java

import javax.swing.*;
import java.awt.event.*;
import java.util.*;
import java.awt.*;
import com.incors.plaf.alloy.*;
import com.incors.plaf.alloy.themes.glass.*;

public class JCheckBoxMenuItem1 extends JFrame implements ActionListener {// 由于我们要处理ActionEvent事件,因此要实作
	// ActionListener界面.

	JTextArea theArea = null;

	public JCheckBoxMenuItem1() {

		super("JCheckBoxMenuItem1");
		theArea = new JTextArea();
		theArea.setEditable(false);
		getContentPane().add(new JScrollPane(theArea));
		JMenuBar MBar = new JMenuBar();
		MBar.setOpaque(true);

		JMenu mfile = buildFileMenu();
		JMenu mstyle = buildStyleMenu();// 调用buildStyleMenu()方法来建立包含JCheckBoxMenuItem的JMenu.

		MBar.add(mfile);
		MBar.add(mstyle);
		setJMenuBar(MBar);
	}// end of JCheckBoxMenuItem1()

	public JMenu buildFileMenu() {

		JMenu thefile = new JMenu("File");
		thefile.setMnemonic('F');

		JMenuItem newf = new JMenuItem("New", new ImageIcon("icons/new24.gif"));
		JMenuItem open = new JMenuItem("Open",
				new ImageIcon("icons/open24.gif"));
		JMenuItem close = new JMenuItem("Close", new ImageIcon(
				"icons/close24.gif"));
		JMenuItem quit = new JMenuItem("Exit",
				new ImageIcon("icons/exit24.gif"));

		newf.setMnemonic('N');
		open.setMnemonic('O');
		close.setMnemonic('L');
		quit.setMnemonic('X');

		newf.setAccelerator(KeyStroke.getKeyStroke('N',
				java.awt.Event.CTRL_MASK, false));
		open.setAccelerator(KeyStroke.getKeyStroke('O',
				java.awt.Event.CTRL_MASK, false));
		close.setAccelerator(KeyStroke.getKeyStroke('L',
				java.awt.Event.CTRL_MASK, false));
		quit.setAccelerator(KeyStroke.getKeyStroke('X',
				java.awt.Event.CTRL_MASK, false));

		// 将File Menu内的三个JMenuItem对象加入事件处理模式.
		newf.addActionListener(this);
		open.addActionListener(this);
		close.addActionListener(this);
		quit.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				System.exit(0);
			}
		});

		thefile.add(newf);
		thefile.add(open);
		thefile.add(close);
		thefile.addSeparator();
		thefile.add(quit);

		return thefile;
	}// end of buildFileMenu()

	public JMenu buildStyleMenu() {
		// 建立新的JMenu组件
		JMenu style = new JMenu("Style");
		// 设置其快捷键
		style.setMnemonic('S');

		JCheckBoxMenuItem Left = new JCheckBoxMenuItem("Left", new ImageIcon(
				"icons/left24.gif"));
		JCheckBoxMenuItem Center = new JCheckBoxMenuItem("Center",
				new ImageIcon("icons/center24.gif"));
		JCheckBoxMenuItem Right = new JCheckBoxMenuItem("Right", new ImageIcon(
				"icons/right24.gif"));
		JCheckBoxMenuItem Justify = new JCheckBoxMenuItem("Justify",
				new ImageIcon("icons/justify24.gif"));

		Left.setMnemonic('L');
		Center.setMnemonic('E');
		Right.setMnemonic('R');
		Justify.setMnemonic('J');

		Left.setAccelerator(KeyStroke.getKeyStroke('L',
				java.awt.Event.SHIFT_MASK, false));
		Center.setAccelerator(KeyStroke.getKeyStroke('E',
				java.awt.Event.SHIFT_MASK, false));
		Right.setAccelerator(KeyStroke.getKeyStroke('R',
				java.awt.Event.SHIFT_MASK, false));
		Justify.setAccelerator(KeyStroke.getKeyStroke('J',
				java.awt.Event.SHIFT_MASK, false));
		// 分别将四个JCheckBoxMenuItem加入事件处理模式.
		Left.addActionListener(this);
		Center.addActionListener(this);
		Right.addActionListener(this);
		Justify.addActionListener(this);

		style.add(Left);
		style.add(Center);
		style.add(Right);
		style.add(Justify);

		return style;
	}// end of buildStyleMenu()

	public void actionPerformed(ActionEvent ae) {
		// 为事件处理区段,在这里是将被点选的JMenuItem组件名称填入JTextArea中.
		try {
			theArea.append("* action '" + ae.getActionCommand()
					+ "' performed. *\n");
		} catch (Exception e) {
			System.out.println("actionPerformed Exception:" + e);
		}
	}

	public static void main(String[] args) {
		SwingUtil.setLookAndFeel();
		JFrame F = new JCheckBoxMenuItem1();
		F.setSize(400, 200);
		F.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});// end of addWindowListener
		F.setVisible(true);
	} // end of main
}// end of class JCheckBoxMenuItem1

class SwingUtil {
	public static final void setLookAndFeel() {
		try {
			Font font = new Font("JFrame", Font.PLAIN, 12);
			Enumeration keys = UIManager.getLookAndFeelDefaults().keys();

			while (keys.hasMoreElements()) {
				Object key = keys.nextElement();
				if (UIManager.get(key) instanceof Font) {
					UIManager.put(key, font);
				}
			}
			AlloyLookAndFeel.setProperty("alloy.isLookAndFeelFrameDecoration",
					"true");
			AlloyTheme theme = new GlassTheme();
			LookAndFeel alloyLnF = new AlloyLookAndFeel(theme);
			UIManager.setLookAndFeel(alloyLnF);
		} catch (UnsupportedLookAndFeelException ex) {
			ex.printStackTrace();
		}
	}
}