JDK8/Java8源码在线阅读
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*
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* accompanied this code).
*
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package java.awt;
import java.awt.peer.MenuItemPeer;
import java.awt.event.*;
import java.util.EventListener;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;
import javax.accessibility.*;
import sun.awt.AWTAccessor;
/**
* All items in a menu must belong to the class
* <code>MenuItem</code>, or one of its subclasses.
* <p>
* The default <code>MenuItem</code> object embodies
* a simple labeled menu item.
* <p>
* This picture of a menu bar shows five menu items:
* <IMG SRC="doc-files/MenuBar-1.gif" alt="The following text describes this graphic."
* style="float:center; margin: 7px 10px;">
* <br style="clear:left;">
* The first two items are simple menu items, labeled
* <code>"Basic"</code> and <code>"Simple"</code>.
* Following these two items is a separator, which is itself
* a menu item, created with the label <code>"-"</code>.
* Next is an instance of <code>CheckboxMenuItem</code>
* labeled <code>"Check"</code>. The final menu item is a
* submenu labeled <code>"More Examples"</code>,
* and this submenu is an instance of <code>Menu</code>.
* <p>
* When a menu item is selected, AWT sends an action event to
* the menu item. Since the event is an
* instance of <code>ActionEvent</code>, the <code>processEvent</code>
* method examines the event and passes it along to
* <code>processActionEvent</code>. The latter method redirects the
* event to any <code>ActionListener</code> objects that have
* registered an interest in action events generated by this
* menu item.
* <P>
* Note that the subclass <code>Menu</code> overrides this behavior and
* does not send any event to the frame until one of its subitems is
* selected.
*
* @author Sami Shaio
*/
public class MenuItem extends MenuComponent implements Accessible {
static {
/* ensure that the necessary native libraries are loaded */
Toolkit.loadLibraries();
if (!GraphicsEnvironment.isHeadless()) {
initIDs();
}
AWTAccessor.setMenuItemAccessor(
new AWTAccessor.MenuItemAccessor() {
public boolean isEnabled(MenuItem item) {
return item.enabled;
}
public String getLabel(MenuItem item) {
return item.label;
}
public MenuShortcut getShortcut(MenuItem item) {
return item.shortcut;
}
public String getActionCommandImpl(MenuItem item) {
return item.getActionCommandImpl();
}
public boolean isItemEnabled(MenuItem item) {
return item.isItemEnabled();
}
});
}
/**
* A value to indicate whether a menu item is enabled
* or not. If it is enabled, <code>enabled</code> will
* be set to true. Else <code>enabled</code> will
* be set to false.
*
* @serial
* @see #isEnabled()
* @see #setEnabled(boolean)
*/
boolean enabled = true;
/**
* <code>label</code> is the label of a menu item.
* It can be any string.
*
* @serial
* @see #getLabel()
* @see #setLabel(String)
*/
String label;
/**
* This field indicates the command tha has been issued
* by a particular menu item.
* By default the <code>actionCommand</code>
* is the label of the menu item, unless it has been
* set using setActionCommand.
*
* @serial
* @see #setActionCommand(String)
* @see #getActionCommand()
*/
String actionCommand;
/**
* The eventMask is ONLY set by subclasses via enableEvents.
* The mask should NOT be set when listeners are registered
* so that we can distinguish the difference between when
* listeners request events and subclasses request them.
*
* @serial
*/
long eventMask;
transient ActionListener actionListener;
/**
* A sequence of key stokes that ia associated with
* a menu item.
* Note :in 1.1.2 you must use setActionCommand()
* on a menu item in order for its shortcut to
* work.
*
* @serial
* @see #getShortcut()
* @see #setShortcut(MenuShortcut)
* @see #deleteShortcut()
*/
private MenuShortcut shortcut = null;
private static final String base = "menuitem";
private static int nameCounter = 0;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = -21757335363267194L;
/**
* Constructs a new MenuItem with an empty label and no keyboard
* shortcut.
* @exception HeadlessException if GraphicsEnvironment.isHeadless()
* returns true.
* @see java.awt.GraphicsEnvironment#isHeadless
* @since JDK1.1
*/
public MenuItem() throws HeadlessException {
this("", null);
}
/**
* Constructs a new MenuItem with the specified label
* and no keyboard shortcut. Note that use of "-" in
* a label is reserved to indicate a separator between
* menu items. By default, all menu items except for
* separators are enabled.
* @param label the label for this menu item.
* @exception HeadlessException if GraphicsEnvironment.isHeadless()
* returns true.
* @see java.awt.GraphicsEnvironment#isHeadless
* @since JDK1.0
*/
public MenuItem(String label) throws HeadlessException {
this(label, null);
}
/**
* Create a menu item with an associated keyboard shortcut.
* Note that use of "-" in a label is reserved to indicate
* a separator between menu items. By default, all menu
* items except for separators are enabled.
* @param label the label for this menu item.
* @param s the instance of <code>MenuShortcut</code>
* associated with this menu item.
* @exception HeadlessException if GraphicsEnvironment.isHeadless()
* returns true.
* @see java.awt.GraphicsEnvironment#isHeadless
* @since JDK1.1
*/
public MenuItem(String label, MenuShortcut s) throws HeadlessException {
this.label = label;
this.shortcut = s;
}
/**
* Construct a name for this MenuComponent. Called by getName() when
* the name is null.
*/
String constructComponentName() {
synchronized (MenuItem.class) {
return base + nameCounter++;
}
}
/**
* Creates the menu item's peer. The peer allows us to modify the
* appearance of the menu item without changing its functionality.
*/
public void addNotify() {
synchronized (getTreeLock()) {
if (peer == null)
peer = Toolkit.getDefaultToolkit().createMenuItem(this);
}
}
/**
* Gets the label for this menu item.
* @return the label of this menu item, or <code>null</code>
if this menu item has no label.
* @see java.awt.MenuItem#setLabel
* @since JDK1.0
*/
public String getLabel() {
return label;
}
/**
* Sets the label for this menu item to the specified label.
* @param label the new label, or <code>null</code> for no label.
* @see java.awt.MenuItem#getLabel
* @since JDK1.0
*/
public synchronized void setLabel(String label) {
this.label = label;
MenuItemPeer peer = (MenuItemPeer)this.peer;
if (peer != null) {
peer.setLabel(label);
}
}
/**
* Checks whether this menu item is enabled.
* @see java.awt.MenuItem#setEnabled
* @since JDK1.0
*/
public boolean isEnabled() {
return enabled;
}
/**
* Sets whether or not this menu item can be chosen.
* @param b if <code>true</code>, enables this menu item;
* if <code>false</code>, disables it.
* @see java.awt.MenuItem#isEnabled
* @since JDK1.1
*/
public synchronized void setEnabled(boolean b) {
enable(b);
}
/**
* @deprecated As of JDK version 1.1,
* replaced by <code>setEnabled(boolean)</code>.
*/
@Deprecated
public synchronized void enable() {
enabled = true;
MenuItemPeer peer = (MenuItemPeer)this.peer;
if (peer != null) {
peer.setEnabled(true);
}
}
/**
* @deprecated As of JDK version 1.1,
* replaced by <code>setEnabled(boolean)</code>.
*/
@Deprecated
public void enable(boolean b) {
if (b) {
enable();
} else {
disable();
}
}
/**
* @deprecated As of JDK version 1.1,
* replaced by <code>setEnabled(boolean)</code>.
*/
@Deprecated
public synchronized void disable() {
enabled = false;
MenuItemPeer peer = (MenuItemPeer)this.peer;
if (peer != null) {
peer.setEnabled(false);
}
}
/**
* Get the <code>MenuShortcut</code> object associated with this
* menu item,
* @return the menu shortcut associated with this menu item,
* or <code>null</code> if none has been specified.
* @see java.awt.MenuItem#setShortcut
* @since JDK1.1
*/
public MenuShortcut getShortcut() {
return shortcut;
}
/**
* Set the <code>MenuShortcut</code> object associated with this
* menu item. If a menu shortcut is already associated with
* this menu item, it is replaced.
* @param s the menu shortcut to associate
* with this menu item.
* @see java.awt.MenuItem#getShortcut
* @since JDK1.1
*/
public void setShortcut(MenuShortcut s) {
shortcut = s;
MenuItemPeer peer = (MenuItemPeer)this.peer;
if (peer != null) {
peer.setLabel(label);
}
}
/**
* Delete any <code>MenuShortcut</code> object associated
* with this menu item.
* @since JDK1.1
*/
public void deleteShortcut() {
shortcut = null;
MenuItemPeer peer = (MenuItemPeer)this.peer;
if (peer != null) {
peer.setLabel(label);
}
}
/*
* Delete a matching MenuShortcut associated with this MenuItem.
* Used when iterating Menus.
*/
void deleteShortcut(MenuShortcut s) {
if (s.equals(shortcut)) {
shortcut = null;
MenuItemPeer peer = (MenuItemPeer)this.peer;
if (peer != null) {
peer.setLabel(label);
}
}
}
/*
* The main goal of this method is to post an appropriate event
* to the event queue when menu shortcut is pressed. However,
* in subclasses this method may do more than just posting
* an event.
*/
void doMenuEvent(long when, int modifiers) {
Toolkit.getEventQueue().postEvent(
new ActionEvent(this, ActionEvent.ACTION_PERFORMED,
getActionCommand(), when, modifiers));
}
/*
* Returns true if the item and all its ancestors are
* enabled, false otherwise
*/
private final boolean isItemEnabled() {
// Fix For 6185151: Menu shortcuts of all menuitems within a menu
// should be disabled when the menu itself is disabled
if (!isEnabled()) {
return false;
}
MenuContainer container = getParent_NoClientCode();
do {
if (!(container instanceof Menu)) {
return true;
}
Menu menu = (Menu)container;
if (!menu.isEnabled()) {
return false;
}
container = menu.getParent_NoClientCode();
} while (container != null);
return true;
}
/*
* Post an ActionEvent to the target (on
* keydown) and the item is enabled.
* Returns true if there is an associated shortcut.
*/
boolean handleShortcut(KeyEvent e) {
MenuShortcut s = new MenuShortcut(e.getKeyCode(),
(e.getModifiers() & InputEvent.SHIFT_MASK) > 0);
MenuShortcut sE = new MenuShortcut(e.getExtendedKeyCode(),
(e.getModifiers() & InputEvent.SHIFT_MASK) > 0);
// Fix For 6185151: Menu shortcuts of all menuitems within a menu
// should be disabled when the menu itself is disabled
if ((s.equals(shortcut) || sE.equals(shortcut)) && isItemEnabled()) {
// MenuShortcut match -- issue an event on keydown.
if (e.getID() == KeyEvent.KEY_PRESSED) {
doMenuEvent(e.getWhen(), e.getModifiers());
} else {
// silently eat key release.
}
return true;
}
return false;
}
MenuItem getShortcutMenuItem(MenuShortcut s) {
return (s.equals(shortcut)) ? this : null;
}
/**
* Enables event delivery to this menu item for events
* to be defined by the specified event mask parameter
* <p>
* Since event types are automatically enabled when a listener for
* that type is added to the menu item, this method only needs
* to be invoked by subclasses of <code>MenuItem</code> which desire to
* have the specified event types delivered to <code>processEvent</code>
* regardless of whether a listener is registered.
*
* @param eventsToEnable the event mask defining the event types
* @see java.awt.MenuItem#processEvent
* @see java.awt.MenuItem#disableEvents
* @see java.awt.Component#enableEvents
* @since JDK1.1
*/
protected final void enableEvents(long eventsToEnable) {
eventMask |= eventsToEnable;
newEventsOnly = true;
}
/**
* Disables event delivery to this menu item for events
* defined by the specified event mask parameter.
*
* @param eventsToDisable the event mask defining the event types
* @see java.awt.MenuItem#processEvent
* @see java.awt.MenuItem#enableEvents
* @see java.awt.Component#disableEvents
* @since JDK1.1
*/
protected final void disableEvents(long eventsToDisable) {
eventMask &= ~eventsToDisable;
}
/**
* Sets the command name of the action event that is fired
* by this menu item.
* <p>
* By default, the action command is set to the label of
* the menu item.
* @param command the action command to be set
* for this menu item.
* @see java.awt.MenuItem#getActionCommand
* @since JDK1.1
*/
public void setActionCommand(String command) {
actionCommand = command;
}
/**
* Gets the command name of the action event that is fired
* by this menu item.
* @see java.awt.MenuItem#setActionCommand
* @since JDK1.1
*/
public String getActionCommand() {
return getActionCommandImpl();
}
// This is final so it can be called on the Toolkit thread.
final String getActionCommandImpl() {
return (actionCommand == null? label : actionCommand);
}
/**
* Adds the specified action listener to receive action events
* from this menu item.
* If l is null, no exception is thrown and no action is performed.
* <p>Refer to <a href="doc-files/AWTThreadIssues.html#ListenersThreads"
* >AWT Threading Issues</a> for details on AWT's threading model.
*
* @param l the action listener.
* @see #removeActionListener
* @see #getActionListeners
* @see java.awt.event.ActionEvent
* @see java.awt.event.ActionListener
* @since JDK1.1
*/
public synchronized void addActionListener(ActionListener l) {
if (l == null) {
return;
}
actionListener = AWTEventMulticaster.add(actionListener, l);
newEventsOnly = true;
}
/**
* Removes the specified action listener so it no longer receives
* action events from this menu item.
* If l is null, no exception is thrown and no action is performed.
* <p>Refer to <a href="doc-files/AWTThreadIssues.html#ListenersThreads"
* >AWT Threading Issues</a> for details on AWT's threading model.
*
* @param l the action listener.
* @see #addActionListener
* @see #getActionListeners
* @see java.awt.event.ActionEvent
* @see java.awt.event.ActionListener
* @since JDK1.1
*/
public synchronized void removeActionListener(ActionListener l) {
if (l == null) {
return;
}
actionListener = AWTEventMulticaster.remove(actionListener, l);
}
/**
* Returns an array of all the action listeners
* registered on this menu item.
*
* @return all of this menu item's <code>ActionListener</code>s
* or an empty array if no action
* listeners are currently registered
*
* @see #addActionListener
* @see #removeActionListener
* @see java.awt.event.ActionEvent
* @see java.awt.event.ActionListener
* @since 1.4
*/
public synchronized ActionListener[] getActionListeners() {
return getListeners(ActionListener.class);
}
/**
* Returns an array of all the objects currently registered
* as <code><em>Foo</em>Listener</code>s
* upon this <code>MenuItem</code>.
* <code><em>Foo</em>Listener</code>s are registered using the
* <code>add<em>Foo</em>Listener</code> method.
*
* <p>
* You can specify the <code>listenerType</code> argument
* with a class literal, such as
* <code><em>Foo</em>Listener.class</code>.
* For example, you can query a
* <code>MenuItem</code> <code>m</code>
* for its action listeners with the following code:
*
* <pre>ActionListener[] als = (ActionListener[])(m.getListeners(ActionListener.class));</pre>
*
* If no such listeners exist, this method returns an empty array.
*
* @param listenerType the type of listeners requested; this parameter
* should specify an interface that descends from
* <code>java.util.EventListener</code>
* @return an array of all objects registered as
* <code><em>Foo</em>Listener</code>s on this menu item,
* or an empty array if no such
* listeners have been added
* @exception ClassCastException if <code>listenerType</code>
* doesn't specify a class or interface that implements
* <code>java.util.EventListener</code>
*
* @see #getActionListeners
* @since 1.3
*/
public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
EventListener l = null;
if (listenerType == ActionListener.class) {
l = actionListener;
}
return AWTEventMulticaster.getListeners(l, listenerType);
}
/**
* Processes events on this menu item. If the event is an
* instance of <code>ActionEvent</code>, it invokes
* <code>processActionEvent</code>, another method
* defined by <code>MenuItem</code>.
* <p>
* Currently, menu items only support action events.
* <p>Note that if the event parameter is <code>null</code>
* the behavior is unspecified and may result in an
* exception.
*
* @param e the event
* @see java.awt.MenuItem#processActionEvent
* @since JDK1.1
*/
protected void processEvent(AWTEvent e) {
if (e instanceof ActionEvent) {
processActionEvent((ActionEvent)e);
}
}
// REMIND: remove when filtering is done at lower level
boolean eventEnabled(AWTEvent e) {
if (e.id == ActionEvent.ACTION_PERFORMED) {
if ((eventMask & AWTEvent.ACTION_EVENT_MASK) != 0 ||
actionListener != null) {
return true;
}
return false;
}
return super.eventEnabled(e);
}
/**
* Processes action events occurring on this menu item,
* by dispatching them to any registered
* <code>ActionListener</code> objects.
* This method is not called unless action events are
* enabled for this component. Action events are enabled
* when one of the following occurs:
* <ul>
* <li>An <code>ActionListener</code> object is registered
* via <code>addActionListener</code>.
* <li>Action events are enabled via <code>enableEvents</code>.
* </ul>
* <p>Note that if the event parameter is <code>null</code>
* the behavior is unspecified and may result in an
* exception.
*
* @param e the action event
* @see java.awt.event.ActionEvent
* @see java.awt.event.ActionListener
* @see java.awt.MenuItem#enableEvents
* @since JDK1.1
*/
protected void processActionEvent(ActionEvent e) {
ActionListener listener = actionListener;
if (listener != null) {
listener.actionPerformed(e);
}
}
/**
* Returns a string representing the state of this <code>MenuItem</code>.
* This method is intended to be used only for debugging purposes, and the
* content and format of the returned string may vary between
* implementations. The returned string may be empty but may not be
* <code>null</code>.
*
* @return the parameter string of this menu item
*/
public String paramString() {
String str = ",label=" + label;
if (shortcut != null) {
str += ",shortcut=" + shortcut;
}
return super.paramString() + str;
}
/* Serialization support.
*/
/**
* Menu item serialized data version.
*
* @serial
*/
private int menuItemSerializedDataVersion = 1;
/**
* Writes default serializable fields to stream. Writes
* a list of serializable <code>ActionListeners</code>
* as optional data. The non-serializable listeners are
* detected and no attempt is made to serialize them.
*
* @param s the <code>ObjectOutputStream</code> to write
* @serialData <code>null</code> terminated sequence of 0
* or more pairs; the pair consists of a <code>String</code>
* and an <code>Object</code>; the <code>String</code>
* indicates the type of object and is one of the following:
* <code>actionListenerK</code> indicating an
* <code>ActionListener</code> object
*
* @see AWTEventMulticaster#save(ObjectOutputStream, String, EventListener)
* @see #readObject(ObjectInputStream)
*/
private void writeObject(ObjectOutputStream s)
throws IOException
{
s.defaultWriteObject();
AWTEventMulticaster.save(s, actionListenerK, actionListener);
s.writeObject(null);
}
/**
* Reads the <code>ObjectInputStream</code> and if it
* isn't <code>null</code> adds a listener to receive
* action events fired by the <code>Menu</code> Item.
* Unrecognized keys or values will be ignored.
*
* @param s the <code>ObjectInputStream</code> to read
* @exception HeadlessException if
* <code>GraphicsEnvironment.isHeadless</code> returns
* <code>true</code>
* @see #removeActionListener(ActionListener)
* @see #addActionListener(ActionListener)
* @see #writeObject(ObjectOutputStream)
*/
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException, HeadlessException
{
// HeadlessException will be thrown from MenuComponent's readObject
s.defaultReadObject();
Object keyOrNull;
while(null != (keyOrNull = s.readObject())) {
String key = ((String)keyOrNull).intern();
if (actionListenerK == key)
addActionListener((ActionListener)(s.readObject()));
else // skip value for unrecognized key
s.readObject();
}
}
/**
* Initialize JNI field and method IDs
*/
private static native void initIDs();
/////////////////
// Accessibility support
////////////////
/**
* Gets the AccessibleContext associated with this MenuItem.
* For menu items, the AccessibleContext takes the form of an
* AccessibleAWTMenuItem.
* A new AccessibleAWTMenuItem instance is created if necessary.
*
* @return an AccessibleAWTMenuItem that serves as the
* AccessibleContext of this MenuItem
* @since 1.3
*/
public AccessibleContext getAccessibleContext() {
if (accessibleContext == null) {
accessibleContext = new AccessibleAWTMenuItem();
}
return accessibleContext;
}
/**
* Inner class of MenuItem used to provide default support for
* accessibility. This class is not meant to be used directly by
* application developers, but is instead meant only to be
* subclassed by menu component developers.
* <p>
* This class implements accessibility support for the
* <code>MenuItem</code> class. It provides an implementation of the
* Java Accessibility API appropriate to menu item user-interface elements.
* @since 1.3
*/
protected class AccessibleAWTMenuItem extends AccessibleAWTMenuComponent
implements AccessibleAction, AccessibleValue
{
/*
* JDK 1.3 serialVersionUID
*/
private static final long serialVersionUID = -217847831945965825L;
/**
* Get the accessible name of this object.
*
* @return the localized name of the object -- can be null if this
* object does not have a name
*/
public String getAccessibleName() {
if (accessibleName != null) {
return accessibleName;
} else {
if (getLabel() == null) {
return super.getAccessibleName();
} else {
return getLabel();
}
}
}
/**
* Get the role of this object.
*
* @return an instance of AccessibleRole describing the role of the
* object
*/
public AccessibleRole getAccessibleRole() {
return AccessibleRole.MENU_ITEM;
}
/**
* Get the AccessibleAction associated with this object. In the
* implementation of the Java Accessibility API for this class,
* return this object, which is responsible for implementing the
* AccessibleAction interface on behalf of itself.
*
* @return this object
*/
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