Module java.desktop
Package javax.sound.midi

Class MidiMessage

  • All Implemented Interfaces:
    Cloneable
    Direct Known Subclasses:
    MetaMessage, ShortMessage, SysexMessage

    public abstract class MidiMessage
extends Object
implements Cloneable
    MidiMessage is the base class for MIDI messages. They include not only the standard MIDI messages that a synthesizer can respond to, but also "meta-events" that can be used by sequencer programs. There are meta-events for such information as lyrics, copyrights, tempo indications, time and key signatures, markers, etc. For more information, see the Standard MIDI Files 1.0 specification, which is part of the Complete MIDI 1.0 Detailed Specification published by the MIDI Manufacturer's Association (http://www.midi.org).

    The base MidiMessage class provides access to three types of information about a MIDI message:

    • The messages's status byte
    • The total length of the message in bytes (the status byte plus any data bytes)
    • A byte array containing the complete message
    MidiMessage includes methods to get, but not set, these values. Setting them is a subclass responsibility.

    The MIDI standard expresses MIDI data in bytes. However, because JavaTM uses signed bytes, the Java Sound API uses integers instead of bytes when expressing MIDI data. For example, the getStatus() method of MidiMessage returns MIDI status bytes as integers. If you are processing MIDI data that originated outside Java Sound and now is encoded as signed bytes, the bytes can be converted to integers using this conversion:

    int i = (int)(byte & 0xFF)

    If you simply need to pass a known MIDI byte value as a method parameter, it can be expressed directly as an integer, using (for example) decimal or hexadecimal notation. For instance, to pass the "active sensing" status byte as the first argument to ShortMessage's setMessage(int) method, you can express it as 254 or 0xFE.

    See Also:
    Track, Sequence, Receiver

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected byte[] data
      The MIDI message data.
      protected int length
      The number of bytes in the MIDI message, including the status byte and any data bytes.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected MidiMessage​(byte[] data)
      Constructs a new MidiMessage.

    • Field Detail

      • data

        protected byte[] data
        The MIDI message data. The first byte is the status byte for the message; subsequent bytes up to the length of the message are data bytes for this message.
        See Also:
        getLength()

      • length

        protected int length
        The number of bytes in the MIDI message, including the status byte and any data bytes.
        See Also:
        getLength()

    • Constructor Detail

      • MidiMessage

        protected MidiMessage​(byte[] data)
        Constructs a new MidiMessage. This protected constructor is called by concrete subclasses, which should ensure that the data array specifies a complete, valid MIDI message.
        Parameters:
        data - an array of bytes containing the complete message. The message data may be changed using the setMessage method.
        See Also:
        setMessage(byte[], int)

    • Method Detail

      • setMessage

        protected void setMessage​(byte[] data,
                          int length)
                   throws InvalidMidiDataException
        Sets the data for the MIDI message. This protected method is called by concrete subclasses, which should ensure that the data array specifies a complete, valid MIDI message.
        Parameters:
        data - the data bytes in the MIDI message
        length - the number of bytes in the data byte array
        Throws:
        InvalidMidiDataException - if the parameter values do not specify a valid MIDI meta message

      • getMessage

        public byte[] getMessage​()
        Obtains the MIDI message data. The first byte of the returned byte array is the status byte of the message. Any subsequent bytes up to the length of the message are data bytes. The byte array may have a length which is greater than that of the actual message; the total length of the message in bytes is reported by the getLength() method.
        Returns:
        the byte array containing the complete MidiMessage data

      • getStatus

        public int getStatus​()
        Obtains the status byte for the MIDI message. The status "byte" is represented as an integer; see the discussion in the MidiMessage class description.
        Returns:
        the integer representation of this event's status byte

      • getLength

        public int getLength​()
        Obtains the total length of the MIDI message in bytes. A MIDI message consists of one status byte and zero or more data bytes. The return value ranges from 1 for system real-time messages, to 2 or 3 for channel messages, to any value for meta and system exclusive messages.
        Returns:
        the length of the message in bytes

      • clone

        public abstract Object clone​()
        Creates a new object of the same class and with the same contents as this object.
        Overrides:
        clone in class Object
        Returns:
        a clone of this instance
        See Also:
        Cloneable