Track (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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Java^TM 2 Platform
Std. Ed. v1.4.1

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javax.sound.midi
Class Track

java.lang.Object
  |
  +--javax.sound.midi.Track

public class Track
extends Object

A MIDI track is an independent stream of MIDI events (time-stamped MIDI data) that can be stored along with other tracks in a standard MIDI file. The MIDI specification allows only 16 channels of MIDI data, but tracks are a way to get around this limitation. A MIDI file can contain any number of tracks, each containing its own stream of up to 16 channels of MIDI data.

A Track occupies a middle level in the hierarchy of data played by a Sequencer: sequencers play sequences, which contain tracks, which contain MIDI events. A sequencer may provide controls that mute or solo individual tracks.

The timing information and resolution for a track is controlled by and stored in the sequence containing the track. A given Track is considered to belong to the particular Sequence that maintains its timing. For this reason, a new (empty) track is created by calling the Sequence.createTrack() method, rather than by directly invoking a Track constructor.

The Track class provides methods to edit the track by adding or removing MidiEvent objects from it. These operations keep the event list in the correct time order. Methods are also included to obtain the track's size, in terms of either the number of events it contains or its duration in ticks.

See Also:: Sequencer.setTrackMute(int, boolean), Sequencer.setTrackSolo(int, boolean)

Field Summary

protected Vector events
          The list of MidiEvents contained in this track.

Method Summary

boolean add(MidiEvent event)
          Adds a new event to the track.

MidiEvent get(int index)
          Obtains the event at the specified index.

boolean remove(MidiEvent event)
          Removes the specified event from the track.

int size()
          Obtains the number of events in this track.

long ticks()
          Obtains the length of the track, expressed in MIDI ticks.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

events

protected Vector events

The list of MidiEvents contained in this track.

Method Detail

add

public boolean add(MidiEvent event)

Adds a new event to the track. However, if the event is already contained in the track, it is not added again. The list of events is kept in time order, meaning that this event inserted at the appropriate place in the list, not necessarily at the end.

Parameters:: event - the event to add
Returns:: true if the event did not already exist in the track and was added, otherwise false

remove

public boolean remove(MidiEvent event)

Removes the specified event from the track.

Parameters:: event - the event to remove
Returns:: true if the event existed in the track and was removed, otherwise false

get

public MidiEvent get(int index)
              throws ArrayIndexOutOfBoundsException

Obtains the event at the specified index.

Parameters:: index - the location of the desired event in the event vector
Throws:: ArrayIndexOutOfBoundsException - if the specified index is negative or not less than the current size of this track.; ArrayIndexOutOfBoundsException
See Also:: size()

size

public int size()

Obtains the number of events in this track.

Returns:: the size of the track's event vector

ticks

public long ticks()

Obtains the length of the track, expressed in MIDI ticks. (The duration of a tick in seconds is determined by the timing resolution of the Sequence containing this track, and also by the tempo of the music as set by the sequencer.)

Returns:: the duration, in ticks
See Also:: Sequence.Sequence(float, int), Sequencer.setTempoInBPM(float), Sequencer.getTickPosition()