/*

 * Copyright (c) 1995, 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.awt;

import java.awt.peer.ButtonPeer;

import java.util.EventListener;

import java.awt.event.*;

import java.io.ObjectOutputStream;

import java.io.ObjectInputStream;

import java.io.IOException;

import javax.accessibility.*;

/**

 * This class creates a labeled button. The application can cause

 * some action to happen when the button is pushed. This image

 * depicts three views of a "<code>Quit</code>" button as it appears

 * under the Solaris operating system:

 * <p>

 * <img src="doc-files/Button-1.gif" alt="The following context describes the graphic"

 * style="float:center; margin: 7px 10px;">

 * <p>

 * The first view shows the button as it appears normally.

 * The second view shows the button

 * when it has input focus. Its outline is darkened to let the

 * user know that it is an active object. The third view shows the

 * button when the user clicks the mouse over the button, and thus

 * requests that an action be performed.

 * <p>

 * The gesture of clicking on a button with the mouse

 * is associated with one instance of <code>ActionEvent</code>,

 * which is sent out when the mouse is both pressed and released

 * over the button. If an application is interested in knowing

 * when the button has been pressed but not released, as a separate

 * gesture, it can specialize <code>processMouseEvent</code>,

 * or it can register itself as a listener for mouse events by

 * calling <code>addMouseListener</code>. Both of these methods are

 * defined by <code>Component</code>, the abstract superclass of

 * all components.

 * <p>

 * When a button is pressed and released, AWT sends an instance

 * of <code>ActionEvent</code> to the button, by calling

 * <code>processEvent</code> on the button. The button's

 * <code>processEvent</code> method receives all events

 * for the button; it passes an action event along by

 * calling its own <code>processActionEvent</code> method.

 * The latter method passes the action event on to any action

 * listeners that have registered an interest in action

 * events generated by this button.

 * <p>

 * If an application wants to perform some action based on

 * a button being pressed and released, it should implement

 * <code>ActionListener</code> and register the new listener

 * to receive events from this button, by calling the button's

 * <code>addActionListener</code> method. The application can

 * make use of the button's action command as a messaging protocol.

 *

 * @author      Sami Shaio

 * @see         java.awt.event.ActionEvent

 * @see         java.awt.event.ActionListener

 * @see         java.awt.Component#processMouseEvent

 * @see         java.awt.Component#addMouseListener

 * @since       1.0

 */

public class Button extends Component implements Accessible {

    /**

     * The button's label.  This value may be null.

     * @serial

     * @see #getLabel()

     * @see #setLabel(String)

     */

    String label;

    /**

     * The action to be performed once a button has been

     * pressed.  This value may be null.

     * @serial

     * @see #getActionCommand()

     * @see #setActionCommand(String)

     */

    String actionCommand;

    transient ActionListener actionListener;

    private static final String base = "button";

    private static int nameCounter = 0;

    /*

     * JDK 1.1 serialVersionUID

     */

    private static final long serialVersionUID = -8774683716313001058L;

    static {

        /* ensure that the necessary native libraries are loaded */

        Toolkit.loadLibraries();

        if (!GraphicsEnvironment.isHeadless()) {

            initIDs();

        }

    }

    /**

     * Initialize JNI field and method IDs for fields that may be

     * accessed from C.

     */

    private static native void initIDs();

    /**

     * Constructs a button with an empty string for its label.

     *

     * @exception HeadlessException if GraphicsEnvironment.isHeadless()

     * returns true

     * @see java.awt.GraphicsEnvironment#isHeadless

     */

    public Button() throws HeadlessException {

        this("");

    }

    /**

     * Constructs a button with the specified label.

     *

     * @param label  a string label for the button, or

     *               <code>null</code> for no label

     * @exception HeadlessException if GraphicsEnvironment.isHeadless()

     * returns true

     * @see java.awt.GraphicsEnvironment#isHeadless

     */

    public Button(String label) throws HeadlessException {

        GraphicsEnvironment.checkHeadless();

        this.label = label;

    }

    /**

     * Construct a name for this component.  Called by getName() when the

     * name is null.

     */

    String constructComponentName() {

        synchronized (Button.class) {

            return base + nameCounter++;

        }

    }

    /**

     * Creates the peer of the button.  The button's peer allows the

     * application to change the look of the button without changing

     * its functionality.

     *

     * @see     java.awt.Toolkit#createButton(java.awt.Button)

     * @see     java.awt.Component#getToolkit()

     */

    public void addNotify() {

        synchronized(getTreeLock()) {

            if (peer == null)

                peer = getToolkit().createButton(this);

            super.addNotify();

        }

    }

    /**

     * Gets the label of this button.

     *

     * @return    the button's label, or <code>null</code>

     *                if the button has no label.

     * @see       java.awt.Button#setLabel

     */

    public String getLabel() {

        return label;

    }

    /**

     * Sets the button's label to be the specified string.

     *

     * @param     label   the new label, or <code>null</code>

     *                if the button has no label.

     * @see       java.awt.Button#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;

                ButtonPeer peer = (ButtonPeer)this.peer;

                if (peer != null) {

                    peer.setLabel(label);

                }

                testvalid = true;

            }

        }

        // This could change the preferred size of the Component.

        if (testvalid) {

            invalidateIfValid();

        }

    }

    /**

     * Sets the command name for the action event fired

     * by this button. By default this action command is

     * set to match the label of the button.

     *

     * @param     command  a string used to set the button's

     *                  action command.

     *            If the string is <code>null</code> then the action command

     *            is set to match the label of the button.

     * @see       java.awt.event.ActionEvent

     * @since     1.1

     */

    public void setActionCommand(String command) {

        actionCommand = command;

    }

    /**

     * Returns the command name of the action event fired by this button.

     * If the command name is <code>null</code> (default) then this method

     * returns the label of the button.

     *

     * @return the action command name (or label) for this button

     */

    public String getActionCommand() {

        return (actionCommand == null? label : actionCommand);

    }

    /**

     * Adds the specified action listener to receive action events from

     * this button. Action events occur when a user presses or releases

     * the mouse over this button.

     * 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.ActionListener

     * @since         1.1

     */

    public synchronized void addActionListener(ActionListener l) {

        if (l == null) {

            return;

        }

        actionListener = AWTEventMulticaster.add(actionListener, l);

        newEventsOnly = true;

    }

    /**

     * Removes the specified action listener so that it no longer

     * receives action events from this button. Action events occur

     * when a user presses or releases the mouse over this button.

     * 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.ActionListener

     * @since           1.1

     */

    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 button.

     *

     * @return all of this button's <code>ActionListener</code>s

     *         or an empty array if no action

     *         listeners are currently registered

     *

     * @see             #addActionListener

     * @see             #removeActionListener

     * @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>Button</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>Button</code> <code>b</code>

     * for its action listeners with the following code:

     *

     * <pre>ActionListener[] als = (ActionListener[])(b.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 button,

     *          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;

        } 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 == ActionEvent.ACTION_PERFORMED) {

            if ((eventMask & AWTEvent.ACTION_EVENT_MASK) != 0 ||

                actionListener != null) {

                return true;

            }

            return false;

        }

        return super.eventEnabled(e);

    }

    /**

     * Processes events on this button. If an event is

     * an instance of <code>ActionEvent</code>, this method invokes

     * the <code>processActionEvent</code> method. Otherwise,

     * it invokes <code>processEvent</code> on the superclass.

     * <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.ActionEvent

     * @see          java.awt.Button#processActionEvent

     * @since        1.1

     */

    protected void processEvent(AWTEvent e) {

        if (e instanceof ActionEvent) {

            processActionEvent((ActionEvent)e);

            return;

        }

        super.processEvent(e);

    }

    /**

     * Processes action events occurring on this button

     * by dispatching them to any registered

     * <code>ActionListener</code> objects.

     * <p>

     * This method is not called unless action events are

     * enabled for this button. 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.ActionListener

     * @see         java.awt.Button#addActionListener

     * @see         java.awt.Component#enableEvents

     * @since       1.1

     */

    protected void processActionEvent(ActionEvent e) {

        ActionListener listener = actionListener;

        if (listener != null) {

            listener.actionPerformed(e);

        }

    }

    /**

     * Returns a string representing the state of this <code>Button</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 button

     */

    protected String paramString() {

        return super.paramString() + ",label=" + label;

    }

    /* Serialization support.

     */

    /*

     * Button Serial Data Version.

     * @serial

     */

    private int buttonSerializedDataVersion = 1;

    /**

     * Writes default serializable fields to stream.  Writes

     * a list of serializable <code>ActionListeners</code>

     * as optional data.  The non-serializable

     * <code>ActionListeners</code> are detected and

     * no attempt is made to serialize them.

     *

     * @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

     *

     * @param s the <code>ObjectOutputStream</code> to write

     * @see AWTEventMulticaster#save(ObjectOutputStream, String, EventListener)

     * @see java.awt.Component#actionListenerK

     * @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 button.

     * 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 #removeActionListener(ActionListener)

     * @see #addActionListener(ActionListener)

     * @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 (actionListenerK == key)

          addActionListener((ActionListener)(s.readObject()));

        else // skip value for unrecognized key

          s.readObject();

      }

    }

/////////////////

// Accessibility support

////////////////

    /**

     * Gets the <code>AccessibleContext</code> associated with

     * this <code>Button</code>. For buttons, the

     * <code>AccessibleContext</code> takes the form of an

     * <code>AccessibleAWTButton</code>.

     * A new <code>AccessibleAWTButton</code> instance is

     * created if necessary.

     *

     * @return an <code>AccessibleAWTButton</code> that serves as the

     *         <code>AccessibleContext</code> of this <code>Button</code>

     * @beaninfo

     *       expert: true

     *  description: The AccessibleContext associated with this Button.

     * @since 1.3

     */

    public AccessibleContext getAccessibleContext() {

        if (accessibleContext == null) {

            accessibleContext = new AccessibleAWTButton();

        }

        return accessibleContext;

    }