JDK8/Java8源码在线阅读
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* accompanied this code).
*
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package java.awt;
import java.awt.peer.CheckboxMenuItemPeer;
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;
/**
* This class represents a check box that can be included in a menu.
* Selecting the check box in the menu changes its state from
* "on" to "off" or from "off" to "on."
* <p>
* The following picture depicts a menu which contains an instance
* of <code>CheckBoxMenuItem</code>:
* <p>
* <img src="doc-files/MenuBar-1.gif"
* alt="Menu labeled Examples, containing items Basic, Simple, Check, and More Examples. The Check item is a CheckBoxMenuItem instance, in the off state."
* style="float:center; margin: 7px 10px;">
* <p>
* The item labeled <code>Check</code> shows a check box menu item
* in its "off" state.
* <p>
* When a check box menu item is selected, AWT sends an item event to
* the item. Since the event is an instance of <code>ItemEvent</code>,
* the <code>processEvent</code> method examines the event and passes
* it along to <code>processItemEvent</code>. The latter method redirects
* the event to any <code>ItemListener</code> objects that have
* registered an interest in item events generated by this menu item.
*
* @author Sami Shaio
* @see java.awt.event.ItemEvent
* @see java.awt.event.ItemListener
* @since JDK1.0
*/
public class CheckboxMenuItem extends MenuItem implements ItemSelectable, Accessible {
static {
/* ensure that the necessary native libraries are loaded */
Toolkit.loadLibraries();
if (!GraphicsEnvironment.isHeadless()) {
initIDs();
}
AWTAccessor.setCheckboxMenuItemAccessor(
new AWTAccessor.CheckboxMenuItemAccessor() {
public boolean getState(CheckboxMenuItem cmi) {
return cmi.state;
}
});
}
/**
* The state of a checkbox menu item
* @serial
* @see #getState()
* @see #setState(boolean)
*/
boolean state = false;
transient ItemListener itemListener;
private static final String base = "chkmenuitem";
private static int nameCounter = 0;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 6190621106981774043L;
/**
* Create a check box menu item with an empty label.
* The item's state is initially set to "off."
* @exception HeadlessException if GraphicsEnvironment.isHeadless()
* returns true
* @see java.awt.GraphicsEnvironment#isHeadless
* @since JDK1.1
*/
public CheckboxMenuItem() throws HeadlessException {
this("", false);
}
/**
* Create a check box menu item with the specified label.
* The item's state is initially set to "off."
* @param label a string label for the check box menu item,
* or <code>null</code> for an unlabeled menu item.
* @exception HeadlessException if GraphicsEnvironment.isHeadless()
* returns true
* @see java.awt.GraphicsEnvironment#isHeadless
*/
public CheckboxMenuItem(String label) throws HeadlessException {
this(label, false);
}
/**
* Create a check box menu item with the specified label and state.
* @param label a string label for the check box menu item,
* or <code>null</code> for an unlabeled menu item.
* @param state the initial state of the menu item, where
* <code>true</code> indicates "on" and
* <code>false</code> indicates "off."
* @exception HeadlessException if GraphicsEnvironment.isHeadless()
* returns true
* @see java.awt.GraphicsEnvironment#isHeadless
* @since JDK1.1
*/
public CheckboxMenuItem(String label, boolean state)
throws HeadlessException {
super(label);
this.state = state;
}
/**
* Construct a name for this MenuComponent. Called by getName() when
* the name is null.
*/
String constructComponentName() {
synchronized (CheckboxMenuItem.class) {
return base + nameCounter++;
}
}
/**
* Creates the peer of the checkbox item. This peer allows us to
* change the look of the checkbox item without changing its
* functionality.
* Most applications do not call this method directly.
* @see java.awt.Toolkit#createCheckboxMenuItem(java.awt.CheckboxMenuItem)
* @see java.awt.Component#getToolkit()
*/
public void addNotify() {
synchronized (getTreeLock()) {
if (peer == null)
peer = Toolkit.getDefaultToolkit().createCheckboxMenuItem(this);
super.addNotify();
}
}
/**
* Determines whether the state of this check box menu item
* is "on" or "off."
*
* @return the state of this check box menu item, where
* <code>true</code> indicates "on" and
* <code>false</code> indicates "off"
* @see #setState
*/
public boolean getState() {
return state;
}
/**
* Sets this check box menu item to the specified state.
* The boolean value <code>true</code> indicates "on" while
* <code>false</code> indicates "off."
*
* <p>Note that this method should be primarily used to
* initialize the state of the check box menu item.
* Programmatically setting the state of the check box
* menu item will <i>not</i> trigger
* an <code>ItemEvent</code>. The only way to trigger an
* <code>ItemEvent</code> is by user interaction.
*
* @param b <code>true</code> if the check box
* menu item is on, otherwise <code>false</code>
* @see #getState
*/
public synchronized void setState(boolean b) {
state = b;
CheckboxMenuItemPeer peer = (CheckboxMenuItemPeer)this.peer;
if (peer != null) {
peer.setState(b);
}
}
/**
* Returns the an array (length 1) containing the checkbox menu item
* label or null if the checkbox is not selected.
* @see ItemSelectable
*/
public synchronized Object[] getSelectedObjects() {
if (state) {
Object[] items = new Object[1];
items[0] = label;
return items;
}
return null;
}
/**
* Adds the specified item listener to receive item events from
* this check box menu item. Item events are sent in response to user
* actions, but not in response to calls to setState().
* 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 item listener
* @see #removeItemListener
* @see #getItemListeners
* @see #setState
* @see java.awt.event.ItemEvent
* @see java.awt.event.ItemListener
* @since JDK1.1
*/
public synchronized void addItemListener(ItemListener l) {
if (l == null) {
return;
}
itemListener = AWTEventMulticaster.add(itemListener, l);
newEventsOnly = true;
}
/**
* Removes the specified item listener so that it no longer receives
* item events from this check box 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 item listener
* @see #addItemListener
* @see #getItemListeners
* @see java.awt.event.ItemEvent
* @see java.awt.event.ItemListener
* @since JDK1.1
*/
public synchronized void removeItemListener(ItemListener l) {
if (l == null) {
return;
}
itemListener = AWTEventMulticaster.remove(itemListener, l);
}
/**
* Returns an array of all the item listeners
* registered on this checkbox menuitem.
*
* @return all of this checkbox menuitem's <code>ItemListener</code>s
* or an empty array if no item
* listeners are currently registered
*
* @see #addItemListener
* @see #removeItemListener
* @see java.awt.event.ItemEvent
* @see java.awt.event.ItemListener
* @since 1.4
*/
public synchronized ItemListener[] getItemListeners() {
return getListeners(ItemListener.class);
}
/**
* Returns an array of all the objects currently registered
* as <code><em>Foo</em>Listener</code>s
* upon this <code>CheckboxMenuItem</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>CheckboxMenuItem</code> <code>c</code>
* for its item listeners with the following code:
*
* <pre>ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.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 checkbox menuitem,
* 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 #getItemListeners
* @since 1.3
*/
public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
EventListener l = null;
if (listenerType == ItemListener.class) {
l = itemListener;
} else {
return super.getListeners(listenerType);
}
return AWTEventMulticaster.getListeners(l, listenerType);
}
// REMIND: remove when filtering is done at lower level
boolean eventEnabled(AWTEvent e) {
if (e.id == ItemEvent.ITEM_STATE_CHANGED) {
if ((eventMask & AWTEvent.ITEM_EVENT_MASK) != 0 ||
itemListener != null) {
return true;
}
return false;
}
return super.eventEnabled(e);
}
/**
* Processes events on this check box menu item.
* If the event is an instance of <code>ItemEvent</code>,
* this method invokes the <code>processItemEvent</code> method.
* If the event is not an item event,
* it invokes <code>processEvent</code> on the superclass.
* <p>
* Check box menu items currently support only item 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.event.ItemEvent
* @see #processItemEvent
* @since JDK1.1
*/
protected void processEvent(AWTEvent e) {
if (e instanceof ItemEvent) {
processItemEvent((ItemEvent)e);
return;
}
super.processEvent(e);
}
/**
* Processes item events occurring on this check box menu item by
* dispatching them to any registered <code>ItemListener</code> objects.
* <p>
* This method is not called unless item events are
* enabled for this menu item. Item events are enabled
* when one of the following occurs:
* <ul>
* <li>An <code>ItemListener</code> object is registered
* via <code>addItemListener</code>.
* <li>Item 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 item event
* @see java.awt.event.ItemEvent
* @see java.awt.event.ItemListener
* @see #addItemListener
* @see java.awt.MenuItem#enableEvents
* @since JDK1.1
*/
protected void processItemEvent(ItemEvent e) {
ItemListener listener = itemListener;
if (listener != null) {
listener.itemStateChanged(e);
}
}
/*
* Post an ItemEvent and toggle state.
*/
void doMenuEvent(long when, int modifiers) {
setState(!state);
Toolkit.getEventQueue().postEvent(
new ItemEvent(this, ItemEvent.ITEM_STATE_CHANGED,
getLabel(),
state ? ItemEvent.SELECTED :
ItemEvent.DESELECTED));
}
/**
* Returns a string representing the state of this
* <code>CheckBoxMenuItem</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 check box menu item
*/
public String paramString() {
return super.paramString() + ",state=" + state;
}
/* Serialization support.
*/
/*
* Serial Data Version
* @serial
*/
private int checkboxMenuItemSerializedDataVersion = 1;
/**
* Writes default serializable fields to stream. Writes
* a list of serializable <code>ItemListeners</code>
* as optional data. The non-serializable
* <code>ItemListeners</code> 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>itemListenerK</code> indicating an
* <code>ItemListener</code> object
*
* @see AWTEventMulticaster#save(ObjectOutputStream, String, EventListener)
* @see java.awt.Component#itemListenerK
* @see #readObject(ObjectInputStream)
*/
private void writeObject(ObjectOutputStream s)
throws java.io.IOException
{
s.defaultWriteObject();
AWTEventMulticaster.save(s, itemListenerK, itemListener);
s.writeObject(null);
}
/*
* Reads the <code>ObjectInputStream</code> and if it
* isn't <code>null</code> adds a listener to receive
* item events fired by the <code>Checkbox</code> menu item.
* Unrecognized keys or values will be ignored.
*
* @param s the <code>ObjectInputStream</code> to read
* @serial
* @see removeActionListener()
* @see addActionListener()
* @see #writeObject
*/
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException
{
s.defaultReadObject();
Object keyOrNull;
while(null != (keyOrNull = s.readObject())) {
String key = ((String)keyOrNull).intern();
if (itemListenerK == key)
addItemListener((ItemListener)(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 CheckboxMenuItem.
* For checkbox menu items, the AccessibleContext takes the
* form of an AccessibleAWTCheckboxMenuItem.
* A new AccessibleAWTCheckboxMenuItem is created if necessary.
*
* @return an AccessibleAWTCheckboxMenuItem that serves as the
* AccessibleContext of this CheckboxMenuItem
* @since 1.3
*/
public AccessibleContext getAccessibleContext() {
if (accessibleContext == null) {
accessibleContext = new AccessibleAWTCheckboxMenuItem();
}
return accessibleContext;
}
/**
* Inner class of CheckboxMenuItem 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>CheckboxMenuItem</code> class. It provides an implementation
* of the Java Accessibility API appropriate to checkbox menu item
* user-interface elements.
* @since 1.3
*/
protected class AccessibleAWTCheckboxMenuItem extends AccessibleAWTMenuItem
implements AccessibleAction, AccessibleValue
{
/*
* JDK 1.3 serialVersionUID
*/
private static final long serialVersionUID = -1122642964303476L;
/**
* 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
*/
public AccessibleAction getAccessibleAction() {
return this;
}
/**
* Get the AccessibleValue associated with this object. In the
* implementation of the Java Accessibility API for this class,
* return this object, which is responsible for implementing the
* AccessibleValue interface on behalf of itself.
*
* @return this object
*/
public AccessibleValue getAccessibleValue() {
return this;
}
/**
* Returns the number of Actions available in this object.
* If there is more than one, the first one is the "default"
* action.
*
* @return the number of Actions in this object
*/
public int getAccessibleActionCount() {
return 0; // To be fully implemented in a future release
}
/**
* Return a description of the specified action of the object.
*
* @param i zero-based index of the actions
*/
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