Java tutorial
/* * Copyright (c) 1996, 2013, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package java.awt.event; import java.awt.AWTEvent; import java.lang.annotation.Native; /** * A semantic event which indicates that a component-defined action occurred. * This high-level event is generated by a component (such as a * {@code Button}) when * the component-specific action occurs (such as being pressed). * The event is passed to every {@code ActionListener} object * that registered to receive such events using the component's * {@code addActionListener} method. * <p> * <b>Note:</b> To invoke an {@code ActionEvent} on a * {@code Button} using the keyboard, use the Space bar. * <P> * The object that implements the {@code ActionListener} interface * gets this {@code ActionEvent} when the event occurs. The listener * is therefore spared the details of processing individual mouse movements * and mouse clicks, and can instead process a "meaningful" (semantic) * event like "button pressed". * <p> * An unspecified behavior will be caused if the {@code id} parameter * of any particular {@code ActionEvent} instance is not * in the range from {@code ACTION_FIRST} to {@code ACTION_LAST}. * * @see ActionListener * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/actionlistener.html">Tutorial: How to Write an Action Listener</a> * * @author Carl Quinn * @since 1.1 */ public class ActionEvent extends AWTEvent { /** * The shift modifier. An indicator that the shift key was held * down during the event. */ public static final int SHIFT_MASK = 1 << 0; /** * The control modifier. An indicator that the control key was held * down during the event. */ public static final int CTRL_MASK = 1 << 1; /** * The meta modifier. An indicator that the meta key was held * down during the event. */ public static final int META_MASK = 1 << 2; /** * The alt modifier. An indicator that the alt key was held * down during the event. */ public static final int ALT_MASK = 1 << 3; /** * The first number in the range of ids used for action events. */ public static final int ACTION_FIRST = 1001; /** * The last number in the range of ids used for action events. */ public static final int ACTION_LAST = 1001; /** * This event id indicates that a meaningful action occurred. */ @Native public static final int ACTION_PERFORMED = ACTION_FIRST; //Event.ACTION_EVENT /** * The nonlocalized string that gives more details * of what actually caused the event. * This information is very specific to the component * that fired it. * @serial * @see #getActionCommand */ String actionCommand; /** * Timestamp of when this event occurred. Because an ActionEvent is a high- * level, semantic event, the timestamp is typically the same as an * underlying InputEvent. * * @serial * @see #getWhen */ long when; /** * This represents the key modifier that was selected, * and is used to determine the state of the selected key. * If no modifier has been selected it will default to * zero. * * @serial * @see #getModifiers */ int modifiers; /* * JDK 1.1 serialVersionUID */ private static final long serialVersionUID = -7671078796273832149L; /** * Constructs an {@code ActionEvent} object. * <p> * This method throws an * {@code IllegalArgumentException} if {@code source} * is {@code null}. * A {@code null command} string is legal, * but not recommended. * * @param source The object that originated the event * @param id An integer that identifies the event. * For information on allowable values, see * the class description for {@link ActionEvent} * @param command A string that may specify a command (possibly one * of several) associated with the event * @throws IllegalArgumentException if {@code source} is null * @see #getSource() * @see #getID() * @see #getActionCommand() */ public ActionEvent(Object source, int id, String command) { this(source, id, command, 0); } /** * Constructs an {@code ActionEvent} object with modifier keys. * <p> * This method throws an * {@code IllegalArgumentException} if {@code source} * is {@code null}. * A {@code null command} string is legal, * but not recommended. * * @param source The object that originated the event * @param id An integer that identifies the event. * For information on allowable values, see * the class description for {@link ActionEvent} * @param command A string that may specify a command (possibly one * of several) associated with the event * @param modifiers The modifier keys down during event * (shift, ctrl, alt, meta). * Passing negative parameter is not recommended. * Zero value means that no modifiers were passed * @throws IllegalArgumentException if {@code source} is null * @see #getSource() * @see #getID() * @see #getActionCommand() * @see #getModifiers() */ public ActionEvent(Object source, int id, String command, int modifiers) { this(source, id, command, 0, modifiers); } /** * Constructs an {@code ActionEvent} object with the specified * modifier keys and timestamp. * <p> * This method throws an * {@code IllegalArgumentException} if {@code source} * is {@code null}. * A {@code null command} string is legal, * but not recommended. * * @param source The object that originated the event * @param id An integer that identifies the event. * For information on allowable values, see * the class description for {@link ActionEvent} * @param command A string that may specify a command (possibly one * of several) associated with the event * @param modifiers The modifier keys down during event * (shift, ctrl, alt, meta). * Passing negative parameter is not recommended. * Zero value means that no modifiers were passed * @param when A long that gives the time the event occurred. * Passing negative or zero value * is not recommended * @throws IllegalArgumentException if {@code source} is null * @see #getSource() * @see #getID() * @see #getActionCommand() * @see #getModifiers() * @see #getWhen() * * @since 1.4 */ public ActionEvent(Object source, int id, String command, long when, int modifiers) { super(source, id); this.actionCommand = command; this.when = when; this.modifiers = modifiers; } /** * Returns the command string associated with this action. * This string allows a "modal" component to specify one of several * commands, depending on its state. For example, a single button might * toggle between "show details" and "hide details". The source object * and the event would be the same in each case, but the command string * would identify the intended action. * <p> * Note that if a {@code null} command string was passed * to the constructor for this {@code ActionEvent}, this * this method returns {@code null}. * * @return the string identifying the command for this event */ public String getActionCommand() { return actionCommand; } /** * Returns the timestamp of when this event occurred. Because an * ActionEvent is a high-level, semantic event, the timestamp is typically * the same as an underlying InputEvent. * * @return this event's timestamp * @since 1.4 */ public long getWhen() { return when; } /** * Returns the modifier keys held down during this action event. * * @return the bitwise-or of the modifier constants */ public int getModifiers() { return modifiers; } /** * Returns a parameter string identifying this action event. * This method is useful for event-logging and for debugging. * * @return a string identifying the event and its associated command */ @SuppressWarnings("deprecation") public String paramString() { String typeStr; switch (id) { case ACTION_PERFORMED: typeStr = "ACTION_PERFORMED"; break; default: typeStr = "unknown type"; } return typeStr + ",cmd=" + actionCommand + ",when=" + when + ",modifiers=" + KeyEvent.getKeyModifiersText(modifiers); } }