track.add，MidiEvent和shortMessage（音量控制）

问题描述

在我的客户端，我试图让MIDI文件淡出，然后继续下一个MIDI序列，但我遇到麻烦。 >使用下面的代码，它会导致一个nullpointerException在 track.add ，我想知道我在做错什么？

我比较新的Java编程，所以请具体在你的答案

  public void run（）{
 active = true 
 String s = findcachedir（）; 
 uid = getuid（s）; 
 
 
 if（midiplay）
 {
 / * 
 midi = s + savereq; 
 midiplay = false; 
 * / 
 
 midi = s + savereq; 
 try {
 //System.out.println(\"Play MIDI+ midi）; 
 if（musicSr！= null）
 {
 musicSr.stop（）; 
 musicSr.close（）; 
} 
 musicSr = null; 
 musicS = null; 
 
文件音乐=新文件（midi）; 
 if（music.exists（））
 {
 musicS = MidiSystem.getSequence（music）; （int k = 0; k  musicS.getTracks（）; 
} 
 
 track.add（
 new MidiEvent（
 new ShortMessage（
 ShortMessage.CONTROL_CHANGE，
k，
 7，
 20），
 track.getTicks（）））; 
} 
 
 //为序列创建序列器
 musicSr = MidiSystem.getSequencer（）; 
 musicSr.open（）; 
 musicSr.setSequence（musicS）; 
 musicSr.setLoopCount（Sequencer.LOOP_CONTINUOUSLY）; 
 musicSr.start（）; 
} catch（Exception ex）{
 ex.printStackTrace（）; 
} 
 
 
 midiplay = false; 
 
} 
 savereq = null; 
} 
 
} 
 
 
 public static Sequencer musicSr = null; 
序列musicS = null; 
  

`
如果您因任何原因需要它，整个课程

解决方案

变量 track 似乎没有被初始化。可能你应该这样做：

  private Track track = new Track（）; 
  

或者如果您实现了getter设置器，然后将值设置为 track 之前使用添加方法。像 setTrack（trackObj）;

On my client I am trying to make MIDI files fade out before continuing on to the next MIDI in the sequence, but I've been having trouble with it.

With the code below, it causes a nullpointerException at track.add, I was wondering what I am doing wrong?

I'm relatively new to Java programming, so please be specific in your answers

public void run() {
    active = true
    String s = findcachedir();
    uid = getuid(s);


            if(midiplay)
            {
                /*
                    midi = s + savereq;
                    midiplay = false;
                 */

                midi = s + savereq;
                try {
                    //System.out.println("Play MIDI " + midi);
                    if (musicSr != null)
                    {
                        musicSr.stop();
                        musicSr.close();
                    }
                    musicSr = null;
                    musicS = null;

                    File music = new File(midi);
                    if(music.exists())
                    {
                        musicS = MidiSystem.getSequence(music);
                    }
                    for (int k = 0; k < 16; k++) {
                        musicS.getTracks();
                        track.add(
                                new MidiEvent(
                                        new ShortMessage(
                                                ShortMessage.CONTROL_CHANGE,
                                                k, 
                                                7,
                                                20),
                                                track.getTicks()));
                    }

                        // Create a sequencer for the sequence
                        musicSr = MidiSystem.getSequencer();
                        musicSr.open();
                        musicSr.setSequence(musicS);
                        musicSr.setLoopCount(Sequencer.LOOP_CONTINUOUSLY);
                        musicSr.start();
                } catch (Exception ex) {
                    ex.printStackTrace();
                }


                midiplay = false;

            }
            savereq = null;
        }

}


public static Sequencer musicSr = null;
Sequence musicS = null;

`The entire class if you need it for any reason

http://pastebin.com/6C7GNnib

解决方案

The variable track seems not to be initialized. May be you should do something like this :

private Track track = new Track();

or if you have getter setters implemented then set the value in track before using add method. Something like setTrack(trackObj);

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