/*
 * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 *
 */
package java.awt;

import java.awt.peer.CheckboxPeer;
import java.awt.event.*;
import java.util.EventListener;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;
import javax.accessibility.*;


/**
 * A check box is a graphical component that can be in either an
 * "on" (<code>true</code>) or "off" (<code>false</code>) state.
 * Clicking on a check box changes its state from
 * "on" to "off," or from "off" to "on."
 * <p>
 * The following code example creates a set of check boxes in
 * a grid layout:
 *
 * <hr><blockquote><pre>
 * setLayout(new GridLayout(3, 1));
 * add(new Checkbox("one", null, true));
 * add(new Checkbox("two"));
 * add(new Checkbox("three"));
 * </pre></blockquote><hr>
 * <p>
 * This image depicts the check boxes and grid layout
 * created by this code example:
 * <p>
 * <img src="doc-files/Checkbox-1.gif" alt="The following context describes the graphic."
 * style="float:center; margin: 7px 10px;">
 * <p>
 * The button labeled <code>one</code> is in the "on" state, and the
 * other two are in the "off" state. In this example, which uses the
 * <code>GridLayout</code> class, the states of the three check
 * boxes are set independently.
 * <p>
 * Alternatively, several check boxes can be grouped together under
 * the control of a single object, using the
 * <code>CheckboxGroup</code> class.
 * In a check box group, at most one button can be in the "on"
 * state at any given time. Clicking on a check box to turn it on
 * forces any other check box in the same group that is on
 * into the "off" state.
 *
 * @author Sami Shaio
 * @see java.awt.GridLayout
 * @see java.awt.CheckboxGroup
 * @since JDK1.0
 */
public class Checkbox extends Component implements ItemSelectable, Accessible {

 static {
 /* ensure that the necessary native libraries are loaded */
 Toolkit.loadLibraries();
 if (!GraphicsEnvironment.isHeadless()) {
 initIDs();
 }
 }

 /**
 * The label of the Checkbox.
 * This field can be null.
 * @serial
 * @see #getLabel()
 * @see #setLabel(String)
 */
 String label;

 /**
 * The state of the <code>Checkbox</code>.
 * @serial
 * @see #getState()
 * @see #setState(boolean)
 */
 boolean state;

 /**
 * The check box group.
 * This field can be null indicating that the checkbox
 * is not a group checkbox.
 * @serial
 * @see #getCheckboxGroup()
 * @see #setCheckboxGroup(CheckboxGroup)
 */
 CheckboxGroup group;

 transient ItemListener itemListener;

 private static final String base = "checkbox";
 private static int nameCounter = 0;

 /*
 * JDK 1.1 serialVersionUID
 */
 private static final long serialVersionUID = 7270714317450821763L;

 /**
 * Helper function for setState and CheckboxGroup.setSelectedCheckbox
 * Should remain package-private.
 */
 void setStateInternal(boolean state) {
 this.state = state;
 CheckboxPeer peer = (CheckboxPeer)this.peer;
 if (peer != null) {
 peer.setState(state);
 }
 }

 /**
 * Creates a check box with an empty string for its label.
 * The state of this check box is set to "off," and it is not
 * part of any check box group.
 * @exception HeadlessException if GraphicsEnvironment.isHeadless()
 * returns true
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 public Checkbox() throws HeadlessException {
 this("", false, null);
 }

 /**
 * Creates a check box with the specified label. The state
 * of this check box is set to "off," and it is not part of
 * any check box group.
 *
 * @param label a string label for this check box,
 * or <code>null</code> for no label.
 * @exception HeadlessException if
 * <code>GraphicsEnvironment.isHeadless</code>
 * returns <code>true</code>
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 public Checkbox(String label) throws HeadlessException {
 this(label, false, null);
 }

 /**
 * Creates a check box with the specified label
 * and sets the specified state.
 * This check box is not part of any check box group.
 *
 * @param label a string label for this check box,
 * or <code>null</code> for no label
 * @param state the initial state of this check box
 * @exception HeadlessException if
 * <code>GraphicsEnvironment.isHeadless</code>
 * returns <code>true</code>
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 public Checkbox(String label, boolean state) throws HeadlessException {
 this(label, state, null);
 }

 /**
 * Constructs a Checkbox with the specified label, set to the
 * specified state, and in the specified check box group.
 *
 * @param label a string label for this check box,
 * or <code>null</code> for no label.
 * @param state the initial state of this check box.
 * @param group a check box group for this check box,
 * or <code>null</code> for no group.
 * @exception HeadlessException if
 * <code>GraphicsEnvironment.isHeadless</code>
 * returns <code>true</code>
 * @see java.awt.GraphicsEnvironment#isHeadless
 * @since JDK1.1
 */
 public Checkbox(String label, boolean state, CheckboxGroup group)
 throws HeadlessException {
 GraphicsEnvironment.checkHeadless();
 this.label = label;
 this.state = state;
 this.group = group;
 if (state && (group != null)) {
 group.setSelectedCheckbox(this);
 }
 }

 /**
 * Creates a check box with the specified label, in the specified
 * check box group, and set to the specified state.
 *
 * @param label a string label for this check box,
 * or <code>null</code> for no label.
 * @param group a check box group for this check box,
 * or <code>null</code> for no group.
 * @param state the initial state of this check box.
 * @exception HeadlessException if
 * <code>GraphicsEnvironment.isHeadless</code>
 * returns <code>true</code>
 * @see java.awt.GraphicsEnvironment#isHeadless
 * @since JDK1.1
 */
 public Checkbox(String label, CheckboxGroup group, boolean state)
 throws HeadlessException {
 this(label, state, group);
 }

 /**
 * Constructs a name for this component. Called by
 * <code>getName</code> when the name is <code>null</code>.
 *
 * @return a name for this component
 */
 String constructComponentName() {
 synchronized (Checkbox.class) {
 return base + nameCounter++;
 }
 }

 /**
 * Creates the peer of the Checkbox. The peer allows you to change the
 * look of the Checkbox without changing its functionality.
 *
 * @see java.awt.Toolkit#createCheckbox(java.awt.Checkbox)
 * @see java.awt.Component#getToolkit()
 */
 public void addNotify() {
 synchronized (getTreeLock()) {
 if (peer == null)
 peer = getToolkit().createCheckbox(this);
 super.addNotify();
 }
 }

 /**
 * Gets the label of this check box.
 *
 * @return the label of this check box, or <code>null</code>
 * if this check box has no label.
 * @see #setLabel(String)
 */
 public String getLabel() {
 return label;
 }

 /**
 * Sets this check box's label to be the string argument.
 *
 * @param label a string to set as the new label, or
 * <code>null</code> for no label.
 * @see #getLabel
 */
 public void setLabel(String label) {
 boolean testvalid = false;

 synchronized (this) {
 if (label != this.label && (this.label == null ||
 !this.label.equals(label))) {
 this.label = label;
 CheckboxPeer peer = (CheckboxPeer)this.peer;
 if (peer != null) {
 peer.setLabel(label);
 }
 testvalid = true;
 }
 }

 // This could change the preferred size of the Component.
 if (testvalid) {
 invalidateIfValid();
 }
 }

 /**
 * Determines whether this check box is in the "on" or "off" state.
 * The boolean value <code>true</code> indicates the "on" state,
 * and <code>false</code> indicates the "off" state.
 *
 * @return the state of this check box, as a boolean value
 * @see #setState
 */
 public boolean getState() {
 return state;
 }

 /**
 * Sets the state of this check box to the specified state.
 * The boolean value <code>true</code> indicates the "on" state,
 * and <code>false</code> indicates the "off" state.
 *
 * <p>Note that this method should be primarily used to
 * initialize the state of the checkbox. Programmatically
 * setting the state of the checkbox will <i>not</i> trigger
 * an <code>ItemEvent</code>. The only way to trigger an
 * <code>ItemEvent</code> is by user interaction.
 *
 * @param state the boolean state of the check box
 * @see #getState
 */
 public void setState(boolean state) {
 /* Cannot hold check box lock when calling group.setSelectedCheckbox. */
 CheckboxGroup group = this.group;
 if (group != null) {
 if (state) {
 group.setSelectedCheckbox(this);
 } else if (group.getSelectedCheckbox() == this) {
 state = true;
 }
 }
 setStateInternal(state);
 }

 /**
 * Returns an array (length 1) containing the checkbox
 * label or null if the checkbox is not selected.
 * @see ItemSelectable
 */
 public Object[] getSelectedObjects() {
 if (state) {
 Object[] items = new Object[1];
 items[0] = label;
 return items;
 }
 return null;
 }

 /**
 * Determines this check box's group.
 * @return this check box's group, or <code>null</code>
 * if the check box is not part of a check box group.
 * @see #setCheckboxGroup(CheckboxGroup)
 */
 public CheckboxGroup getCheckboxGroup() {
 return group;
 }

 /**
 * Sets this check box's group to the specified check box group.
 * If this check box is already in a different check box group,
 * it is first taken out of that group.
 * <p>
 * If the state of this check box is <code>true</code> and the new
 * group already has a check box selected, this check box's state
 * is changed to <code>false</code>. If the state of this check
 * box is <code>true</code> and the new group has no check box
 * selected, this check box becomes the selected checkbox for
 * the new group and its state is <code>true</code>.
 *
 * @param g the new check box group, or <code>null</code>
 * to remove this check box from any check box group
 * @see #getCheckboxGroup
 */
 public void setCheckboxGroup(CheckboxGroup g) {
 CheckboxGroup oldGroup;
 boolean oldState;

 /* Do nothing if this check box has already belonged
 * to the check box group g.
 */
 if (this.group == g) {
 return;
 }

 synchronized (this) {
 oldGroup = this.group;
 oldState = getState();

 this.group = g;
 CheckboxPeer peer = (CheckboxPeer)this.peer;
 if (peer != null) {
 peer.setCheckboxGroup(g);
 }
 if (this.group != null && getState()) {
 if (this.group.getSelectedCheckbox() != null) {
 setState(false);
 } else {
 this.group.setSelectedCheckbox(this);
 }
 }
 }

 /* Locking check box below could cause deadlock with
 * CheckboxGroup's setSelectedCheckbox method.
 *
 * Fix for 4726853 by kdm@sparc.spb.su
 * Here we should check if this check box was selected
 * in the previous group and set selected check box to
 * null for that group if so.
 */
 if (oldGroup != null && oldState) {
 oldGroup.setSelectedCheckbox(null);
 }
 }

 /**
 * Adds the specified item listener to receive item events from
 * this check box. Item events are sent to listeners in response
 * to user input, 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 the item listener
 * no longer receives item events from this check box.
 * 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.
 *
 * @return all of this checkbox'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>Checkbox</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>Checkbox</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,
 * 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.
 * If the event is an instance of <code>ItemEvent</code>,
 * this method invokes the <code>processItemEvent</code> method.
 * Otherwise, it calls its superclass's <code>processEvent</code> method.
 * <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 by
 * dispatching them to any registered
 * <code>ItemListener</code> objects.
 * <p>
 * This method is not called unless item events are
 * enabled for this component. 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.Component#enableEvents
 * @since JDK1.1
 */
 protected void processItemEvent(ItemEvent e) {
 ItemListener listener = itemListener;
 if (listener != null) {
 listener.itemStateChanged(e);
 }
 }

 /**
 * Returns a string representing the state of this <code>Checkbox</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
 */
 protected String paramString() {
 String str = super.paramString();
 String label = this.label;
 if (label != null) {
 str += ",label=" + label;
 }
 return str + ",state=" + state;
 }


 /* Serialization support.
 */

 /*
 * Serialized data version
 * @serial
 */
 private int checkboxSerializedDataVersion = 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>.
 * 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>
 * @serial
 * @see #removeItemListener(ItemListener)
 * @see #addItemListener(ItemListener)
 * @see java.awt.GraphicsEnvironment#isHeadless
 * @see #writeObject(ObjectOutputStream)
 */
 private void readObject(ObjectInputStream s)
 throws ClassNotFoundException, IOException, HeadlessException
 {
 GraphicsEnvironment.checkHeadless();
 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 Checkbox.
 * For checkboxes, the AccessibleContext takes the form of an
 * AccessibleAWTCheckbox.
 * A new AccessibleAWTCheckbox is created if necessary.
 *
 * @return an AccessibleAWTCheckbox that serves as the
 * AccessibleContext of this Checkbox
 * @since 1.3
 */
 public AccessibleContext getAccessibleContext() {
 if (accessibleContext == null) {
 accessibleContext = new AccessibleAWTCheckbox();
 }
 return accessibleContext;
 }

 /**
 * This class implements accessibility support for the
 * <code>Checkbox</code> class. It provides an implementation of the
 * Java Accessibility API appropriate to checkbox user-interface elements.
 * @since 1.3
 */
 protected class AccessibleAWTCheckbox extends AccessibleAWTComponent
 implements ItemListener, AccessibleAction, AccessibleValue
 {
 /*
 * JDK 1.3 serialVersionUID
 */
 private static final long serialVersionUID = 7881579233144754107L;

 public AccessibleAWTCheckbox() {
 super();
 Checkbox.this.addItemListener(this);
 }

 /**
 * Fire accessible property change events when the state of the
 * toggle button changes.
 */
 public void itemStateChanged(ItemEvent e) {
 Checkbox cb = (Checkbox) e.getSource();
 if (Checkbox.this.accessibleContext != null) {
 if (cb.getState()) {
 Checkbox.this.accessibleContext.firePropertyChange(
 AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
 null, AccessibleState.CHECKED);
 } else {
 Checkbox.this.accessibleContext.firePropertyChange(
 AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
 AccessibleState.CHECKED, null);
 }
 }
 }

 /**
 * 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
 */
 public String getAccessibleActionDescription(int i) {
 return null; // To be fully implemented in a future release
 }

 /**
 * Perform the specified Action on the object
 *
 * @param i zero-based index of actions
 * @return true if the the action was performed; else 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.
 *
 * @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.
 *
 * @return True if the value was set; else 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.
 *
 * @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.
 *
 * @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.
 *
 * @return an instance of AccessibleRole describing the role of
 * the object
 * @see AccessibleRole
 */
 public AccessibleRole getAccessibleRole() {
 return AccessibleRole.CHECK_BOX;
 }

 /**
 * Get the state set of this object.
 *
 * @return an instance of AccessibleState containing the current state
 * of the object
 * @see AccessibleState
 */
 public AccessibleStateSet getAccessibleStateSet() {
 AccessibleStateSet states = super.getAccessibleStateSet();
 if (getState()) {
 states.add(AccessibleState.CHECKED);
 }
 return states;
 }


 } // inner class AccessibleAWTCheckbox

}