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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."

The following picture depicts a menu which contains an instance of CheckBoxMenuItem:

The item labeled Check shows a check box menu item in its "off" state.

When a check box menu item is selected, AWT sends an item event to the item. Since the event is an instance of ItemEvent, the processEvent method examines the event and passes it along to processItemEvent. The latter method redirects the event to any ItemListener objects that have registered an interest in item events generated by this menu item.

Author: Sami Shaio
See Also:
Since: JDK1.0
/** * 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
See Also:
@serial
/** * 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."
Throws:
  • HeadlessException – if GraphicsEnvironment.isHeadless() returns true
See Also:
Since: JDK1.1
/** * 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."
Params:
  • label – a string label for the check box menu item, or null for an unlabeled menu item.
Throws:
See Also:
/** * 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.
Params:
  • label – a string label for the check box menu item, or null for an unlabeled menu item.
  • state – the initial state of the menu item, where true indicates "on" and false indicates "off."
Throws:
See Also:
Since: JDK1.1
/** * 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.
/** * 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 Also:
/** * 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."
See Also:
Returns: the state of this check box menu item, where true indicates "on" and false indicates "off"
/** * 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 true indicates "on" while false indicates "off."

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 not trigger an ItemEvent. The only way to trigger an ItemEvent is by user interaction.

Params:
  • b – true if the check box menu item is on, otherwise false
See Also:
/** * 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 Also:
  • ItemSelectable
/** * 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.

Refer to AWT Threading Issues for details on AWT's threading model.

Params:
  • l – the item listener
See Also:
Since: JDK1.1
/** * 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.

Refer to AWT Threading Issues for details on AWT's threading model.

Params:
  • l – the item listener
See Also:
Since: JDK1.1
/** * 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.
See Also:
Returns:all of this checkbox menuitem's ItemListeners or an empty array if no item listeners are currently registered
Since:1.4
/** * 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 FooListeners upon this CheckboxMenuItem. FooListeners are registered using the addFooListener method.

You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a CheckboxMenuItem c for its item listeners with the following code:

ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class));
If no such listeners exist, this method returns an empty array.
Params:
  • listenerType – the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener
Throws:
  • ClassCastException – if listenerType doesn't specify a class or interface that implements java.util.EventListener
See Also:
Returns:an array of all objects registered as FooListeners on this checkbox menuitem, or an empty array if no such listeners have been added
Since:1.3
/** * 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 ItemEvent, this method invokes the processItemEvent method. If the event is not an item event, it invokes processEvent on the superclass.

Check box menu items currently support only item events.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Params:
  • e – the event
See Also:
Since: JDK1.1
/** * 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 ItemListener objects.

This method is not called unless item events are enabled for this menu item. Item events are enabled when one of the following occurs:

  • An ItemListener object is registered via addItemListener.
  • Item events are enabled via enableEvents.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Params:
  • e – the item event
See Also:
Since: JDK1.1
/** * 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 CheckBoxMenuItem. 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 null.
Returns: the parameter string of this check box menu item
/** * 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 ItemListeners as optional data. The non-serializable ItemListeners are detected and no attempt is made to serialize them.
Params:
  • s – the ObjectOutputStream to write
See Also:
@serialDatanull terminated sequence of 0 or more pairs; the pair consists of a String and an Object; the String indicates the type of object and is one of the following: itemListenerK indicating an ItemListener object
/** * 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
/** * 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.
Returns:an AccessibleAWTCheckboxMenuItem that serves as the AccessibleContext of this CheckboxMenuItem
Since:1.3
/** * 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.

This class implements accessibility support for the CheckboxMenuItem class. It provides an implementation of the Java Accessibility API appropriate to checkbox menu item user-interface elements.

Since:1.3
/** * 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.
Returns:this object
/** * 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.
Returns:this object
/** * 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.
Returns:the number of Actions in this object
/** * 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.
Params:
  • i – zero-based index of the actions
/** * Return a description of the specified action of the object. * * @param i zero-based index of the actions */
public String getAccessibleActionDescription(int i) { return null; // To be fully implemented in a future release }
Perform the specified Action on the object
Params:
  • i – zero-based index of actions
Returns:true if the action was performed; otherwise false.
/** * Perform the specified Action on the object * * @param i zero-based index of actions * @return true if the action was performed; otherwise false. */
public boolean doAccessibleAction(int i) { return false; // To be fully implemented in a future release }
Get the value of this object as a Number. If the value has not been set, the return value will be null.
See Also:
Returns:value of the object
/** * Get the value of this object as a Number. If the value has not been * set, the return value will be null. * * @return value of the object * @see #setCurrentAccessibleValue */
public Number getCurrentAccessibleValue() { return null; // To be fully implemented in a future release }
Set the value of this object as a Number.
See Also:
Returns:true if the value was set; otherwise false
/** * Set the value of this object as a Number. * * @return true if the value was set; otherwise false * @see #getCurrentAccessibleValue */
public boolean setCurrentAccessibleValue(Number n) { return false; // To be fully implemented in a future release }
Get the minimum value of this object as a Number.
See Also:
Returns:Minimum value of the object; null if this object does not have a minimum value
/** * Get the minimum value of this object as a Number. * * @return Minimum value of the object; null if this object does not * have a minimum value * @see #getMaximumAccessibleValue */
public Number getMinimumAccessibleValue() { return null; // To be fully implemented in a future release }
Get the maximum value of this object as a Number.
See Also:
Returns:Maximum value of the object; null if this object does not have a maximum value
/** * Get the maximum value of this object as a Number. * * @return Maximum value of the object; null if this object does not * have a maximum value * @see #getMinimumAccessibleValue */
public Number getMaximumAccessibleValue() { return null; // To be fully implemented in a future release }
Get the role of this object.
Returns:an instance of AccessibleRole describing the role of the object
/** * Get the role of this object. * * @return an instance of AccessibleRole describing the role of the * object */
public AccessibleRole getAccessibleRole() { return AccessibleRole.CHECK_BOX; } } // class AccessibleAWTMenuItem }