SWING 5 menu (lập TRÌNH NÂNG CAO SLIDE)

The Menu API : javax.swing.JMenu public JMenuItem addString s Creates a new menu item with the specified text and appends it to the end of this menu.. Parameters:s - the string for the

PHẦN 2 - SWING

MENUS

Menu look

The Menu Component Hierarchy

The Menu Structure

 //Create the menu bar.

menuBar = new JMenuBar();

setJMenuBar(menuBar);

Creating Menus

//Build the first menu.

menu = new JMenu(“File");

menu.setMnemonic(KeyEvent.VK_F);

menuBar.add(menu);

//a group of JMenuItems

menuItem = new JMenuItem("New ", KeyEvent.VK_N);

//used constructor instead

//menuItem.setMnemonic(KeyEvent.VK_N);

menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyE vent.VK_1, ActionEvent.ALT_MASK));

menuItem.addActionListener(this);

Creating Menus

//Menu item with Text and Icon

menuItem = new JMenuItem("Open ",

new ImageIcon("images/middle.gif")); menuItem.setMnemonic(KeyEvent.VK_O);

menuItem.addActionListener(this);

menu.add(menuItem);

//Menu item has only a Icon

menuItem = new JMenuItem(new

ImageIcon("images/middle.gif"));

menuItem.setMnemonic(KeyEvent.VK_D);

menuItem.addActionListener(this);

Creating Menus

//a group of radio button menu items

menu.addSeparator();

ButtonGroup group = new ButtonGroup();

rbMenuItem = new JRadioButtonMenuItem("A radio

button menu item 1“);

rbMenuItem = new JRadioButtonMenuItem("A radio

button menu item 2“);

rbMenuItem.setMnemonic(KeyEvent.VK_2);

group.add(rbMenuItem);

rbMenuItem.addActionListener(this);

menu.add(rbMenuItem);

//Build second menu in the menu bar.

menu = new JMenu("Options");

menu.setMnemonic(KeyEvent.VK_P);

menuBar.add(menu);

Handling Events from Menu Items

 public class MenuDemo implements ActionListener,

public void actionPerformed(ActionEvent e) {

// Get information from the action event

// Display it in the text area }

public void itemStateChanged(ItemEvent e) {

// Get information from the item event

// Display it in the text area

}

How to Write an Item Listener

//where initialization occurs

The Item Event API

 void itemStateChanged(ItemEvent)

Called just after a state change in the listened-to component

 The itemStateChanged method hod has a single parameter: an ItemEvent object The ItemEvent class defines the following

How to Use Actions

If you have two or more components that perform the same function, consider using an Action object to

implement the function An Action object is an

ActionListener that provides not only action-event

handling, but also centralized handling of the text ,

icon , and enabled state of tool bar buttons or menu

items By adding an Action to a JToolBar , JMenu , or

JPopupMenu , you should to use Actions

Action leftAction = new AbstractAction ( );

Button button = toolBar.add( leftAction );

JMenuItem menuItem = mainMenu.add( leftAction );

 Action exitAction = new AbstractAction("Exit") {

public void actionPerformed(ActionEvent event)

{ // action code goes here

System.exit(0);

} };

 You can then add the action to the menu:

JMenuItem exitItem = fileMenu.add(exitAction);

 This command adds a menu item to the menu, using the action name The action object becomes its

listener This is just a convenient shortcut for

JMenuItem exitItem = new JMenuItem(exitAction); fileMenu.add(exitItem);

Enabling Keyboard Operation

 Menus support two kinds of keyboard alternatives:

mnemonics and accelerators

 You can specify a mnemonic either when constructing the menu item or with the setMnemonic method To specify an accelerator, use the setAccelerator method Here are

examples of setting mnemonics and accelerators:

 //Setting the mnemonic when constructing a menu item:

menuItem = new JMenuItem("A text-only menu item",

Enabling and Disabling Menu Items

 To enable or disable a menu item, use the setEnabled

method:

saveItem.setEnabled(false);

 There are two strategies for enabling and disabling menu items Each time circumstances change, you can call

setEnabled on the relevant menu items or actions For

example, as soon as a document has been set to

read-only mode, you can locate the Save and Save As menu

items and disable them Alternatively, you can disable

items just before displaying the menu To do this, you

must register a listener for the "menu selected" event The javax.swing.event package defines a MenuListener

interface with three methods:

Enabling and Disabling Menu Items

void menuSelected(MenuEvent evt)

void menuDeselected(MenuEvent evt)

void menuCanceled(MenuEvent evt)

The menuSelected method is called before the menu is displayed It can therefore be used to disable or enable menu items The following code shows how to disable the Save and Save As actions whenever the Read Only check box menu item is selected:

public void menuSelected(MenuEvent evt) {

saveAction.setEnabled(!readonlyItem.isSelected());

saveAsAction.setEnabled(!readonlyItem.isSelected())

The Menu API : javax.swing.JMenuBar

 public JMenuBar()

Creates a new menu bar

 public JMenu add(JMenu c)

Appends the specified menu to the end of the menu bar Parameters:c - the JMenu component to add

Returns:the menu component

 public JMenu add(JMenu c)

Appends the specified menu to the end of the menu bar Parameters:c - the JMenu component to add

Returns:the menu component

 public int getMenuCount()

Returns the number of items in the menu bar Returns:the number of items in the menu bar

The Menu API : javax.swing.JMenu

 public JMenuItem add(JMenuItem menuItem)

Appends a menu item to the end of this menu

Returns the menu item added

Parameters:menuItem - the JMenuitem to be added

Returns:the JMenuItem added

 public Component add(Component c, int index)

Adds the specified component to this container at the

The Menu API : javax.swing.JMenu

 public JMenuItem add(String s)

Creates a new menu item with the specified text and

appends it to the end of this menu

Parameters:s - the string for the menu item to be added

 public JMenuItem add(Action a)

Creates a new menu item attached to the specified Action object and appends it to the end of this menu

Parameters:a - the Action for the menu item to be added

 public void addSeparator()

Appends a new separator to the end of the menu

 public void insert(String s, int pos)

Inserts a new menu item with the specified text at a given position

Parameters:s - the text for the menu item to addpos - an integer specifying the position at which to add the new

menu item

The Menu API : javax.swing.JMenu

 public JMenuItem insert(JMenuItem mi,int pos)

Inserts the specified JMenuitem at a given position

Parameters:mi - the JMenuitem to addpos - an integer

specifying the position at which to add the new Jmenuitem

 public JMenuItem insert(Action a, int pos)

Inserts a new menu item attached to the specified Action object at a given position

Parameters:a - the Action object for the menu item to

addpos - an integer specifying the position at which to add the new menu item

 public JMenuItem getItem(int pos)

Returns the JMenuItem at the specified position If the

component at pos is not a menu item, null is returned

Parameters:pos - an integer specifying the position

Returns:the menu item at the specified position; or null if

The Menu API : javax.swing.JMenu

 public void remove(int pos)

Removes the menu item at the specified index from this menu

Parameters:pos - the position of the item to be

removed

 public void removeAll()

Removes all menu items from this menu

 public void addMenuListener(MenuListener l)

Adds a listener for menu events

The Menu API : javax.swing.JMenuItem

 public JMenuItem(Icon icon)

Creates a JMenuItem with the specified icon

Parameters:icon - the icon of the JMenuItem

 public JMenuItem(String text)

Creates a JMenuItem with the specified text

Parameters:text - the text of the JMenuItem

 public JMenuItem(Action a)

Creates a menu item whose properties are taken from the specified Action

Parameters:a - the action of the JMenuItem

 public JMenuItem(String text, Icon icon)

Creates a JMenuItem with the specified text and icon

Parameters:text - the text of the JMenuItem

The Menu API : javax.swing.JMenuItem

 public JMenuItem(String text, int mnemonic)

Creates a JMenuItem with the specified text and keyboard mnemonic

Parameters:text - the text of the JMenuItem

mnemonic - the keyboard mnemonic for the JMenuItem

 public void setEnabled(boolean b)

Enables or disables the menu item

 public void setAccelerator(KeyStroke keyStroke)

Sets the key combination which invokes the menu item's action listeners without navigating the menu hierarchy

Note that when the keyboard accelerator is typed, it will work whether or not the menu is currently displayed

Parameters:keyStroke - the KeyStroke which will serve as

an accelerator

The Menu API : javax.swing.JFrame

 void setJMenuBar(JMenuBar menubar)

sets the menu bar for this frame.

 public JCheckBoxMenuItem(Icon icon)

Creates an initially unselected check box menu item with

an icon

Parameters:icon - the icon of the CheckBoxMenuItem

 public JCheckBoxMenuItem(String text)

Creates an initially unselected check box menu item with text

Parameters:text - the text of the CheckBoxMenuItem

 public JCheckBoxMenuItem(Action a)

Creates a menu item whose properties are taken from the Action supplied

 public JCheckBoxMenuItem(String text, Icon icon)

Creates an initially unselected check box menu item with the specified text and icon

Parameters:text - the text of the CheckBoxMenuItem

icon - the icon of the CheckBoxMenuItem

Parameters:text - the text of the check box menu item.

b - the selected state of the check box menu item

 public JCheckBoxMenuItem(String text, Icon icon,

boolean b)

Creates a check box menu item with the specified text,

icon, and selection state

Parameters:text - the text of the check box menu item

icon - the icon of the check box menu item

b - the selected state of the check box menu item

 public boolean getState()

Returns the selected-state of the item This method

exists for AWT compatibility only New code should

use isSelected() instead

Returns:true if the item is selected

 public void setState(boolean b)

Sets the selected-state of the item This method exists for AWT compatibility only New code should use

setSelected() instead

Parameters:b - a boolean value indicating the item's selected-state, where true=selected

 public JRadioButtonMenuItem(Icon icon)

Creates a JRadioButtonMenuItem with an icon

Parameters:icon - the Icon to display on the

JRadioButtonMenuItem

 public JRadioButtonMenuItem(String text)

Creates a JRadioButtonMenuItem with text

Parameters:text - the text of the JRadioButtonMenuItem

 public JRadioButtonMenuItem(Action a)

Creates a radio button menu item whose properties are

taken from the Action supplied

Parameters:a - the Action on which to base the radio button menu item

 public JRadioButtonMenuItem(String text, Icon icon)

Creates a radio button menu item with the specified text and Icon

Parameters:text - the text of the JRadioButtonMenuItem

Parameters:text - the text of the CheckBoxMenuItem

selected - the selected state of the CheckBoxMenuItem

 public JRadioButtonMenuItem(Icon icon, boolean

selected)

Creates a radio button menu item with the specified image and selection state, but no text

Parameters:icon - the image that the button should display

selected - if true, the button is initially selected;

otherwise, the button is initially unselected

 public JRadioButtonMenuItem(String text, Icon icon,boolean selected)

Creates a radio button menu item that has the

specified text, image, and selection state All other

constructors defer to this one

Parameters:text - the string displayed on the radio

button

icon - the image that the button should display

 public ButtonGroup()

Creates a new ButtonGroup

 public void add(AbstractButton b)

Adds the button to the group

Parameters:b - the button to be added

 public void remove(AbstractButton b)

Removes the button from the group

Parameters:b - the button to be removed