Menu (AWT)

(Steven Shi, hi.steven@gmail.com, jdk 1.4.0, 2002/06/04)

底下的範例程式示範如何用AWT提供的功能表單類別實作出功能表單，要特別注意的是CheckboxMenuItem的event要implement ItemListener，和MenuItem implement ActionListener不一樣，其中ItemListener要改寫itemStateChanged，ActionListener要改寫actionPerformed。

範例程式:

import java.applet.Applet;

import java.awt.*;

import java.awt.event.*;

public class myMenu extends Applet implements ActionListener {

Button m_btnDisplay;

myMenuFrame m_mfWindow;

public void init() {

m_btnDisplay = new Button("Display the menu Window");

add(m_btnDisplay);

m_btnDisplay.addActionListener(this);

m_mfWindow = new myMenuFrame("Sample");

m_mfWindow.setSize(300, 200);

}

public void actionPerformed(ActionEvent event) {

if (event.getSource() == m_btnDisplay) {

m_mfWindow.setVisible(true);

this.setVisible(false);

}

}

}

class myMenuFrame extends Frame implements ActionListener, ItemListener {

MenuBar m_mbMB;

Menu m_mnFile, m_mnNew;

MenuItem m_miNewProject, m_miNewFile;

MenuItem m_miOpen, m_miSave, m_miExit;

CheckboxMenuItem m_cmAutoSave;

Label m_lblMsg;

myMenuFrame(String strTitle) {

super(strTitle);

m_lblMsg = new Label("Hello world!");

this.add(m_lblMsg, BorderLayout.SOUTH);

//功能表

m_mbMB = new MenuBar();

m_mnFile = new Menu("File");

m_mnNew = new Menu("New");

//子功能選單

m_miNewProject = new MenuItem("New Project");

m_miNewProject.setActionCommand("NewProject");

m_miNewProject.addActionListener(this);

m_mnNew.add(m_miNewProject);

m_miNewFile = new MenuItem("New File");

m_miNewFile.setActionCommand("NewFile");

m_miNewFile.addActionListener(this);

m_mnNew.add(m_miNewFile);

m_mnFile.add(m_mnNew);

//功能選單

m_miSave = new MenuItem("Save");

m_miSave.setActionCommand("Save");

m_miSave.addActionListener(this);

m_mnFile.add(m_miSave);

//加分隔線

m_mnFile.addSeparator();

//Checkbox功能選單

m_cmAutoSave = new CheckboxMenuItem("Auto Save");

m_cmAutoSave.setActionCommand("AutoSave");

m_cmAutoSave.addItemListener(this);

m_mnFile.add(m_cmAutoSave);

//加分隔線

m_mnFile.addSeparator();

//功能選單

m_miExit = new MenuItem("Exit");

m_miExit.setActionCommand("Exit");

m_miExit.addActionListener(this);

m_mnFile.add(m_miExit);

m_mbMB.add(m_mnFile);

setMenuBar(m_mbMB);

addWindowListener(

new WindowAdapter() {

public void windowClosing(WindowEvent e) {

System.exit(0);

}

}

);

}

public void actionPerformed(ActionEvent event) {

if (event.getActionCommand().equalsIgnoreCase("NewProject")) {

m_lblMsg.setText("New Project");

}

else if (event.getActionCommand().equalsIgnoreCase("NewFile")) {

m_lblMsg.setText("New File");

}

else if (event.getActionCommand().equalsIgnoreCase("Save")) {

m_lblMsg.setText("Save");

}

else if (event.getActionCommand().equalsIgnoreCase("Exit")) {

m_lblMsg.setText("Exit");

System.exit(0);

}

else {

m_lblMsg.setText("Error: " + event.getActionCommand());

}

}

public void itemStateChanged(ItemEvent event) {

if (event.getSource() == m_cmAutoSave) {

if (((CheckboxMenuItem) event.getItemSelectable()).getState()) {

m_lblMsg.setText("AutoSave is checked");

}

else {

m_lblMsg.setText("AutoSave is not checked");

}

}

}

}