Objectives • Be able to add a menu to the menu bar • Be able to use nested menus
ID: 3663449 • Letter: O
Question
Objectives •
Be able to add a menu to the menu bar •
Be able to use nested menus •
Be able to add scroll bars, giving the user the option of when they will be seen •
Be able to change the look and feel, giving the user the option of which look and feel to use
Introduction
In this lab we will be creating a simple note taking interface. It is currently a working program, but we will be adding features to it. The current program displays a window which has one item on the menu bar, Notes, which allows the user 6 choices. These choices allow the user to store and retrieve up to 2 different notes. It also allows the user to clear the text area or exit the program. We would like to add features to this program which allows the user to change how the user interface appears. We will be adding another choice on the menu bar called Views, giving the user choices about scroll bars and the look and feel of the GUI.
Task #1 Creating a Menu with Submenus
1. Copy the file NoteTaker.java (code listing 12.1) from www.aw.com/cssupport or as directed by your instructor.
2. Compile and run the program. Observe the horizontal menu bar at the top which has only one menu choice, Notes. We will be adding an item to this menu bar called Views that has two submenus. One named Look and Feel and one named Scroll Bars. The submenu named Look and Feel lets the user change the look and feels: Metal, Motif, and Windows. The submenu named Scroll Bars offers the user three choices: Never, Always, and As Needed. When the user makes a choice, the scroll bars are displayed according to the choice.
3. We want to logically break down the problem and make our program easier to read and understand. We will write separate methods to create each of the vertical menus. The three methods that we will be writing are createViews(), createScrollBars(), and createLookAndFeel(). The method headings with empty bodies are provided.
4. Let’s start with the createLookAndFeel() method. This will create the first submenu shown in figure 1. There are three items on this menu, Metal, Motif, and Windows. We will create this menu by doing the following: a) Create a new JMenu with the name Look and Feel. b) Create a new JMenuItem with the name Metal. c) Add an action listener to the menu item (see the createNotes() method to see how this is done). d) Add the menu item to the menu. e) Repeat steps b through d for each of the other two menu items.
5. Similarly, write the createScrollBars() method to create a JMenu that has three menu items, Never, Always, and As Needed. See figure 2.
6. Now that we have our submenus, these menus will become menu items for the Views menu. The createViews() method will make the vertical menu shown cascading from the menu choice Views as shown in figure. We will do this as follows a) Create a new JMenu with the name Views. b) Call the createLookAndFeel() method to create the Look and Feel submenu. c) Add an action listener to the Look and Feel menu. d) Add the look and feel menu to the Views menu. e) Repeat steps b through d for the Scroll Bars menu item, this time calling the createScrollBars() method.
7. Finish creating your menu system by adding the Views menu to the menu bar in the constructor.
Task #2 Adding Scroll Bars and Editing the Action Listener
1. Add scroll bars to the text area by completing the following steps in the constructor a) Create a JScrollPane object called scrolledText, passing in theText. b) Change the line that adds to the textPanel, by passing in scrolledText (which now has theText.)
2. Edit the action listener by adding 6 more branches to the else-if logic. Each branch will compare the actionCommand to the 6 submenu items: Metal, Motif, Window, Never, Always, and As Needed. a) Each Look and Feel submenu item will use a try-catch statement to set the look and feel to the appropriate one, displaying an error message if this was not accomplished. b) Each Scroll Bars submenu item will set the horizontal and vertical scroll bar policy to the appropriate values. c) Any components that have already been created need to be updated. This can be accomplished by calling the SwingUtilities.updateComponentTreeUI method, passing a reference to the component that you want to update as an argument. Specifically you will need to add the line SwingUtilities.updateComponentTreeUIgetContentPane()); to each branch that you just added to the logic structure.
Code Listing 12.1 (NoteTaker.java)
import javax.swing.*; import java.awt.*; import java.awt.event.*;
public class NoteTaker extends JFrame { //constants for set up of note taking area public static final int WIDTH = 600; public static final int HEIGHT = 300; public static final int LINES = 13; public static final int CHAR_PER_LINE = 45;
//objects in GUI private JTextArea theText; //area to take notes private JMenuBar mBar; //horizontal menu bar private JPanel textPanel; //panel to hold scrolling text //area private JMenu notesMenu; //vertical menu with choices for //notes
//****THESE ITEMS ARE NOT YET USED. //****YOU WILL BE CREATING THEM IN THIS LAB private JMenu viewMenu; //vertical menu with choices for //views private JMenu lafMenu; //vertical menu with look and feel private JMenu sbMenu; //vertical menu with scroll bar option private JScrollPane scrolledText;//scroll bars
//default notes private String note1 = "No Note 1."; private String note2 = "No Note 2.";
//constructor public NoteTaker()
{
//create a closeable JFrame with a specific size super("Note Taker"); setSize(WIDTH, HEIGHT); setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
//set layout of the window setLayout(new BorderLayout());
//creates the vertical menus createNotes(); createViews();
//creates horizontal menu bar and //adds vertical menus to it mBar = new JMenuBar(); mBar.add(notesMenu); //****ADD THE viewMenu TO THE MENU BAR HERE setJMenuBar(mBar);
//creates a panel to take notes on textPanel = new JPanel(); textPanel.setBackground(Color.BLUE); theText = new JTextArea(LINES, CHAR_PER_LINE); theText.setBackground(Color.WHITE); //****CREATE A JScrollPane OBJECT HERE CALLED //****scrolledText AND PASS IN theText, THEN //****CHANGE THE LINE BELOW BY PASSING IN scrolledText textPanel.add(theText); add(textPanel, BorderLayout.CENTER);
}
//creates vertical menu associated with Notes //menu item on menu bar public void createNotes() {
notesMenu = new JMenu("Notes"); JMenuItem item;
item = new JMenuItem("Save Note 1"); item.addActionListener(new MenuListener()); notesMenu.add(item);
item = new JMenuItem("Save Note 2"); item.addActionListener(new MenuListener()); notesMenu.add(item);
item = new JMenuItem("Open Note 1"); item.addActionListener(new MenuListener()); notesMenu.add(item);
item = new JMenuItem("Open Note 2"); item.addActionListener(new MenuListener()); notesMenu.add(item);
item = new JMenuItem("Clear"); item.addActionListener(new MenuListener()); notesMenu.add(item);
item = new JMenuItem("Exit"); item.addActionListener(new MenuListener()); notesMenu.add(item);
}
//creates vertical menu associated with Views //menu item on the menu bar public void createViews() {
}
//creates the look and feel submenu public void createLookAndFeel()
{
}
//creates the scroll bars submenu public void createScrollBars() {
}
private class MenuListener implements ActionListener { public void actionPerformed(ActionEvent e) { String actionCommand = e.getActionCommand(); if (actionCommand.equals("Save Note 1")) note1 = theText.getText(); else if (actionCommand.equals("Save Note 2")) note2 = theText.getText(); else if (actionCommand.equals("Clear")) theText.setText(""); else if (actionCommand.equals("Open Note 1")) theText.setText(note1); else if (actionCommand.equals("Open Note 2")) theText.setText(note2); else if (actionCommand.equals("Exit")) System.exit(0); //****ADD 6 BRANCHES TO THE ELSE-IF STRUCTURE //****TO ALLOW ACTION TO BE PERFORMED FOR EACH //****MENU ITEM YOU HAVE CREATED else theText.setText("Error in memo interface"); } }
public static void main(String[] args) { NoteTaker gui = new NoteTaker(); gui.setVisible(true); }
}
Explanation / Answer
Menu bar
}
Scrollbar
Because this code has no event handling, the menus do nothing useful except to look as they should. If you run the example, you'll notice that despite the lack of custom event handling, menus and submenus appear when they should, and the check boxes and radio buttons respond appropriately when the user chooses them.
As the code shows, to set the menu bar for a JFrame, you use the setJMenuBar method. To add a JMenu to a JMenuBar, you use the add(JMenu) method. To add menu items and submenus to a JMenu, you use the add(JMenuItem) method.
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