Killer Game Programming in Java

The Midi Sequences Loader

MidisLoader stores sequences as a collection of MidiInfo objects in a HashMap, keyed by their names. The name and filename for a sequence are obtained from an information file loaded when MidisLoader is created. The file is assumed to be in the subdirectory Sounds/.

MidisLoader allows a specified sequence to be played, stopped, resumed, and looped. A SoundsWatcher can be attached to the sequencer and not to a sequence. MidisLoader deliberately offers almost the same interface as ClipsLoader (see Figure 8-2), though it has some internal differences.

MidisLoader was designed to have one Sequencer object for playing all the sequences, which avoids the overhead of supporting multiple sequencers. Consequently, one sequence will play at a time. This contrasts with ClipsLoader, where multiple clips can be playing concurrently since multiple Clip objects are created by ClipsLoader. A reference to the sequencer is passed to each MidiInfo object, thereby giving them the responsibility for playing, stopping, resuming and looping their sequences.

The MidisLoader initializes the sequencer using initSequencer() and loads the information file:

    // globals
    private Sequencer sequencer;
    private HashMap midisMap;
    private MidiInfo currentMidi = null;
          // reference to currently playing MidiInfo object


    public MidisLoader()
    { midisMap = new HashMap();
      initSequencer();
    }

    public MidisLoader(String soundsFnm)
    { midisMap = new HashMap();
      initSequencer();
      loadSoundsFile(soundsFnm); ...