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.
*
* Although this class implements Serializable, attempts to
* serialize a LineEvent object will fail.
*
* @author Kara Kytle
*
* @see Line
* @see LineListener#update
* @since 1.3
*
* @serial exclude
*/
public class LineEvent extends java.util.EventObject {
private static final long serialVersionUID = -1274246333383880410L;
// INSTANCE VARIABLES
/**
* The kind of line event (OPEN, CLOSE,
* START, or 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 START and 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}.
* @serial
* @see #getFramePosition
*/
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 (OPEN, CLOSE, START, or 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 line is
* 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.
*
* Note that this field is relevant only to certain events generated by
* data lines, such as START and 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
*/
/*
* $$kk: 04.20.99: note to myself: should make sure our implementation is consistent with this.
* which is a reasonable definition....
*/
public final long getFramePosition() {
return position;
}
/**
* Obtains a string representation of the event. The contents of the string may vary
* between implementations of Java Sound.
* @return a string describing the event.
*/
public String toString() {
String sType = "";
if (type != null) sType = type.toString()+" ";
String sLine;
if (getLine() == null) {
sLine = "null";
} else {
sLine = getLine().toString();
}
return new String(sType + "event from line " + sLine);
}
/**
* The LineEvent.Type inner class identifies what kind of event occurred on a line.
* Static instances are provided for the common types (OPEN, CLOSE, START, and STOP).
*
* @see LineEvent#getType()
*/
public static class Type {
/**
* Type name.
*/
// $$kk: 03.25.99: why can't this be final??
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 true if the objects are identical.
* @param obj the reference object with which to compare
* @return true if this event type is the same as
* obj; false otherwise
*/
public final boolean equals(Object obj) {
return super.equals(obj);
}
/**
* Finalizes the hashcode method.
*/
public final int hashCode() {
return super.hashCode();
}
/**
* Returns the type name as the string representation.
*/
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");
} // class Type
} // class LineEvent