最小化和處理問題

Question

嘗試創建一個聲音采樣器，使其可以以不同的頻率/速率播放錄制的樣本，並且正在使用TickRate更改播放速率，類似於TickRate示例。 當我運行時，我在這里得到NullPointerException player.patch(rateControl).patch(out); 但不知道為什么，為什么有任何想法？

import ddf.minim.*;
import ddf.minim.analysis.*;
import ddf.minim.signals.*;
import ddf.minim.ugens.*;
import ddf.minim.spi.*;

Minim minim;
AudioOutput out;
AudioSample sample1;

AudioInput in;
AudioRecorder recorder;
boolean recorded;
FilePlayer player;
TickRate rateControl;

void setup()
{

  size(512, 200, P3D);
  minim = new Minim(this);

  in = minim.getLineIn(Minim.STEREO, 512);

  recorder = minim.createRecorder(in, "myrecording2.wav");
  rateControl = new TickRate(1.f);
  out = minim.getLineOut(Minim.STEREO, 512);
  player.patch(rateControl).patch(out);


  textFont(createFont("Arial", 12));

}

void draw()
{
  if ( recorder.isRecording() )
  {
    fill(255,255,255);
    text("Now recording, press the r key to stop recording.", 5, 310);
  }
  else if ( !recorded )
  {
    fill(255,255,255);
    text("Press the r key to start recording.", 5, 315);
  }
  else
  {
    fill(255,255,255);
    text("Press the q key to save the recording to disk as a sample.", 5, 315);

  }

    for(int i = 0; i < out.bufferSize() - 1; i++)
  {
    float x1 = map(i, 0, out.bufferSize(), 0, width);
    float x2 = map(i+1, 0, out.bufferSize(), 0, width);
    line(x1, 50 + out.left.get(i)*50, x2, 50 + out.left.get(i+1)*50);
    line(x1, 150 + out.right.get(i)*50, x2, 150 + out.right.get(i+1)*50);
  }

}

void keyReleased()
{
  if ( !recorded && key == 'r' ) 
  {
    if ( recorder.isRecording() ) 
    {
      recorder.endRecord();
      recorded = true;
    }
    else 
    {
      recorder.beginRecord();
    }
  }
  if ( recorded && key == 'q' )
  {
    player = new FilePlayer( recorder.save() );
    sample1 = minim.loadSample( "myrecording.wav" , 512 );
    if ( sample1 == null ) println("didn't get sample");
  }
}

void keyPressed()
{
  if ( key == 's' ) 
  {
    sample1.trigger();
  }

  else if ( key == 'd' )
  {
    rateControl.value.setLastValue(3.0f);
    sample1.trigger();
  }

}

Answer 1

您只能在keyReleased()函數中將player設置為等於某個值。 因此，運行setup()時， player仍具有默認的null值。

退后一步，您應該養成調試代碼的習慣。 當您收到NullPointerException ，請嘗試打印出該行上每個變量的值。 您會發現哪個為null ，然后可以找出原因。