ISB16003-OOP Jan2010

Chapter 8

Prepared by :Puan Robiah Hamzah

Advanced Graphical User Interface- JmenuItem

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Objectives

Create menus using components JMenuBar, JMenu, JMenuItem, JCheckBoxMenuItem and JRadioButton

ISB16003-OOP Jan2010

Swing components

In previous lesson, you were introduced to only two components (JButton, JTextField) and several containers (JFrame and JPanel)

Here are some of the Swing components :

AbstractButton

JButton

JToggleButtonJCheckBox

JRadioButton

JLabel

JTextComponent

JComponent

JComboBox

JSlider

JScrollBar

JList

JTextArea

JTextField

Frequently used Swing GUI components

JMenuItem

JCheckBoxMenuItem

JMenu

JRadioButtonMenuItem

JPasswordField

::

…

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Creating menus

Java provides 5 classes that implement menus : 1) JMenuBar2) JMenu 3) JMenuItem 4) JCheckBoxMenuItem

5) JRadioButtonMenuItem Menu bar hold the menus Menu hold the menu items (select or toggle on/off) A menu item can be an instance of 3, 4 or 5 above

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.

1. Create a menu bar and associate it with a frame :

JFrame frame = new JFrame(“MyMenus);

frame.setSize(300,200);

frame.setVisible(true);

JMenuBar jmb = new JMenuBar();

frame.setJMenuBar(jmb); Attach a menu bar to a frame

2. Create menus and associate them with the menu bar

JMenu fileMenu = new JMenu(“File”);

JMenu helpMenu = new JMenu(“Help”);

jmb.add(fileMenu);

jmb.add(helpMenu);

Add two menus into the menu bar

Creating menus (cont)

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Creating menus (cont)

3. Create menus items and add them to the menu (File menu)

fileMenu.add(new JMenuItem(“New”));

fileMenu.add(new JMenuItem(“Open”));

fileMenu.addSeparator();

fileMenu.add(new JMenuItem(“Print”));

fileMenu.addSeparator();

fileMenu.add(new JMenuItem(“Exit”));

4. Create submenu items for “Software” submenu in Help menu

separator

JMenu swHelpSubMenu = new JMenu(”Software”);

helpMenu.add(swHelpSubMenu);

swHelpSubMenu.add(new JMenuItem(“Unix”));

swHelpSubMenu.add(new JMenuItem(“NT”));

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Creating menus (cont)

5. Create check box menu items and add into Help menu

helpMenu.add(new JCheckBoxMenuItem(“Check it”));

6. Create radio button menu items

JMenu clrHelpSubMenu = new JMenu(”Color”);

helpMenu.add(clrHelpSubMenu);

JRadioButtonMenuItem jrbmiBlue,jrbmiYellow, jrbmiRed;

clrHelpSubMenu.add(jrbmiBlue = new JRadioButtonMenuItem(“Blue”));

clrHelpSubMenu.add(jrbmiYellow = new JRadioButtonMenuItem(“Yellow”));

clrHelpSubMenu.add(jrbmiRed = new JRadioButtonMenuItem(“Red”));

ButtonGroup btg = new ButtonGroup();

btg.add(jrbmiBlue);

btg.add(jrbmiBlue);

btg.add(jrbmiBlue);

Group of mutually exclusive choices

3 explicit references here will be grouped later

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Menu item event handling

The menu item generates ActionEvent. Your program must implement the ActionListener and actionPerformed handler to respond to the menu selection.

The following is an example :public void actionPerformed(ActionEvent e)

{ String actionCommand = e.getActionCommand();

if (e.getSource() instanceof JMenuItem)

{ if (“New” equals(actionCommand))

respondToNew(); //responds to “New” menu item

else

:

}

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An example of GUI application Create menus using components JMenuBar, JMenu and JMenuItem:

Write a program that create a user interface to perform arithmetic.The interface contains labels and text fields for Number 1, Number 2 and Result. The Result textfield displays the result of the arithmetic operation between Number 1 and Number 2. Figure 2 below is the sample output of the program. You have to include the menu bar, menu and menu item as part of the interface.

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Guideline for GUI exercise

import java.awt.*;import java.awt.event.*;import javax.swing.*;

public class MyMenuDemo extends JFrame implements ActionListener {// Text fields for Number 1, Number 2, and Result private JTextField jtfNum1, jtfNum2, jtfResult;

// Buttons "Add", "Subtract", "Multiply" and "Divide" private JButton jbtAdd, jbtSub, jbtMul, jbtDiv;

// Menu items "Add", "Subtract", "Multiply","Divide" and "Close" private JMenuItem jmiAdd, jmiSub, jmiMul, jmiDiv, jmiClose;

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Guideline for GUI exercise (cont)public MyMenuDemo() {

1) Create menu bar

2) Add menu “Operation” and “Exit” to menu bar

3) Add menu items to menu “Operation” and “Exit”

4) Create p1 that holds the labels and textfields

5) Create p2 that holds the buttons

6) Add menu bar and the 2 panels to frame content pane

Container container = getContentPane();container.add(jmb,BorderLayout.NORTH);container.add(p1, BorderLayout.CENTER);container.add(p2, BorderLayout.SOUTH);

7) Register listener to each source object

8) Handle ActionEvent from buttons and menu items

i. If (user clicks JButton)

handle button event

else

if (user select JMenuItem)

handle menu item event

Buttons and menu items

String actionCommand = e.getActionCommandif (e.getSource() instanceof JButton) if(“Add”.equals(actionCommand)) calculate(‘+’); else if(“Substract”.equals(actionCommand)) calculate(‘-’); :

Today, add those statements in blue..

(A)

(B)

Done by example

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Guideline for GUI exercise (cont)8) ii. Write the calculate() method

private void calculate (char operator){ int num1 = (Integer.parseInt(jtfNum1.getText().trim())); int num2 = (Integer.parseInt(jtfNum1.getText().trim())); int result = 0;

switch(operator) { case ’+’: result= num1+num2; break; : } jtfResult.setText(String.valueOf(result);

Obtain num1 and num2

Set result in jtfResult

Note : Don’t forget to repeat code (B) for handling menu item event

9) Write the main() with the usual content

(C)

Get rid of blank spaces