Java tutorial
/* * Copyright (c) 1999, 2018, 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 javax.sound.sampled; import java.util.EventObject; /** * The {@code LineEvent} class encapsulates information that a line sends its * listeners whenever the line opens, closes, starts, or stops. Each of these * four state changes is represented by a corresponding type of event. A * listener receives the event as a parameter to its * {@link LineListener#update update} method. By querying the event, the * listener can learn the type of event, the line responsible for the event, and * how much data the line had processed when the event occurred. * <p> * Although this class implements Serializable, attempts to serialize a * {@code LineEvent} object will fail. * * @author Kara Kytle * @see Line * @see LineListener#update * @since 1.3 * * @serial exclude */ public class LineEvent extends EventObject { /** * Use serialVersionUID from JDK 1.3 for interoperability. */ private static final long serialVersionUID = -1274246333383880410L; /** * The kind of line event ({@code OPEN}, {@code CLOSE}, {@code START}, or * {@code STOP}). * * @see #getType * @serial */ private final Type type; /** * The media position when the event occurred, expressed in sample frames. * Note that this field is only relevant to certain events generated by data * lines, such as {@code START} and {@code STOP}. For events generated by * lines that do not count sample frames, and for any other events for which * this value is not known, the position value should be * {@link AudioSystem#NOT_SPECIFIED}. * * @see #getFramePosition * @serial */ private final long position; /** * Constructs a new event of the specified type, originating from the * specified line. * * @param line the source of this event * @param type the event type ({@code OPEN}, {@code CLOSE}, {@code START}, * or {@code STOP}) * @param position the number of sample frames that the line had already * processed when the event occurred, or * {@link AudioSystem#NOT_SPECIFIED} * @throws IllegalArgumentException if {@code line} is {@code null} */ public LineEvent(Line line, Type type, long position) { super(line); this.type = type; this.position = position; } /** * Obtains the audio line that is the source of this event. * * @return the line responsible for this event */ public final Line getLine() { return (Line) getSource(); } /** * Obtains the event's type. * * @return this event's type ({@link Type#OPEN}, {@link Type#CLOSE}, * {@link Type#START}, or {@link Type#STOP}) */ public final Type getType() { return type; } /** * Obtains the position in the line's audio data when the event occurred, * expressed in sample frames. For example, if a source line had already * played back 14 sample frames at the time it was paused, the pause event * would report the line's position as 14. The next frame to be processed * would be frame number 14 using zero-based numbering, or 15 using * one-based numbering. * <p> * Note that this field is relevant only to certain events generated by data * lines, such as {@code START} and {@code STOP}. For events generated by * lines that do not count sample frames, and for any other events for which * this value is not known, the position value should be * {@link AudioSystem#NOT_SPECIFIED}. * * @return the line's position as a sample frame number */ /* * $$kk: 04.20.99: note to myself: should make sure our implementation is * consistent with this. * which is a reasonable definition.... */ public final long getFramePosition() { return position; } /** * Obtains a string representation of the event. The contents of the string * may vary between implementations of Java Sound. * * @return a string describing the event */ @Override public String toString() { String sType = ""; if (type != null) sType = type.toString() + " "; String sLine; if (getLine() == null) { sLine = "null"; } else { sLine = getLine().toString(); } return new String(sType + "event from line " + sLine); } /** * The LineEvent.Type inner class identifies what kind of event occurred on * a line. Static instances are provided for the common types (OPEN, CLOSE, * START, and STOP). * * @see LineEvent#getType() */ public static class Type { /** * Type name. */ private final String name; /** * Constructs a new event type. * * @param name name of the type */ protected Type(String name) { this.name = name; } //$$fb 2002-11-26: fix for 4695001: SPEC: description of equals() method contains typo /** * Indicates whether the specified object is equal to this event type, * returning {@code true} if the objects are the same. * * @param obj the reference object with which to compare * @return {@code true} if the specified object is equal to this event * type; {@code false} otherwise */ @Override public final boolean equals(Object obj) { return super.equals(obj); } /** * Returns a hash code value for this event type. * * @return a hash code value for this event type */ @Override public final int hashCode() { return super.hashCode(); } /** * Returns the type name as the string representation. * * @return the type name as the string representation */ @Override public String toString() { return name; } // LINE EVENT TYPE DEFINES /** * A type of event that is sent when a line opens, reserving system * resources for itself. * * @see #CLOSE * @see Line#open */ public static final Type OPEN = new Type("Open"); /** * A type of event that is sent when a line closes, freeing the system * resources it had obtained when it was opened. * * @see #OPEN * @see Line#close */ public static final Type CLOSE = new Type("Close"); /** * A type of event that is sent when a line begins to engage in active * input or output of audio data in response to a * {@link DataLine#start start} request. * * @see #STOP * @see DataLine#start */ public static final Type START = new Type("Start"); /** * A type of event that is sent when a line ceases active input or * output of audio data in response to a {@link DataLine#stop stop} * request, or because the end of media has been reached. * * @see #START * @see DataLine#stop */ public static final Type STOP = new Type("Stop"); /** * A type of event that is sent when a line ceases to engage in active * input or output of audio data because the end of media has been * reached. */ /* * ISSUE: we may want to get rid of this. Is JavaSound responsible for * reporting this?? * * [If it's decided to keep this API, the docs will need to be updated * to include mention of EOM events elsewhere.] */ //public static final Type EOM = new Type("EOM"); /** * A type of event that is sent when a line begins to engage in active * input or output of audio data. Examples of when this happens are when * a source line begins or resumes writing data to its mixer, and when a * target line begins or resumes reading data from its mixer. * * @see #STOP * @see SourceDataLine#write * @see TargetDataLine#read * @see DataLine#start */ //public static final Type ACTIVE = new Type("ACTIVE"); /** * A type of event that is sent when a line ceases active input or * output of audio data. * * @see #START * @see DataLine#stop */ //public static final Type INACTIVE = new Type("INACTIVE"); } }