Question

I’m building a drum machine/sequencer application, where the user selects a pattern of checkboxes (that are in a grid format: each column is a different beat, each row is a different instrument), and on clicking “play” an audio sample should hopefully play on each selected beat in the pattern.

Currently, I’m using a java.swing timer to run the note() method in a loop. However, this makes it play on every “beat”, whereas I only want it to play on selected beats. I have a feeling I need to use timer.stop() and timer.start() somewhere, so that note() won’t execute on the unselected beats but will start again when it encounters the next selected beat.

I created the array int pattern[] = {1,0,1,0}; to hold the pattern I want the sound to play in. I was thinking there might be a way to cycle through the array and execute note() each time the value is 1, but I don’t really know how it would be done.

So I guess the main question is: how to I get timer to trigger (or not trigger) an event in a pattern? Are any of my inclinations correct, or am I approaching this in the wrong way?
Grateful for any suggestions/advice 🙂

Here’s what I have so far:

import java.io.*;
import javax.sound.sampled.*;
import javax.swing.Timer;
import java.awt.event.*;

public class PlaySound extends JFrame {

static String folderPath = "folder/path/goes/here/";
public static String fileName = "kick_01.wav";
int pattern[] = {1,0,1,0};
int c = 0;

   // Constructor
   public PlaySound() {
       Timer timer = new Timer(500, new ActionListener() { //500 == 120bpm
           public void actionPerformed(ActionEvent e) {
               note(fileName); //Play audio file
       }
   });
   timer.start();
   }

   public static void note(String f) {
   try {
       try {
             // Open an audio input stream.
             File soundFile = new File(folderPath + f);
             AudioInputStream audioIn = AudioSystem.getAudioInputStream(soundFile);
             // Get a soundjava clip resource.
             Clip clip = AudioSystem.getClip();
             // Open audio clip and load samples from the audio input stream.
             clip.open(audioIn);
             clip.start();
          } catch (UnsupportedAudioFileException e) {
             e.printStackTrace();
          } catch (IOException e) {
             e.printStackTrace();
          } catch (LineUnavailableException e) {
             e.printStackTrace();
          }
   } catch (Exception e) {}
   }

}

Answer 1

Keep track of where you are in the pattern every time the Timer fires. Something like:

if (pattern[index] == 1)
    playSound();

index++;

if (index == pattern.length)
    index = 0;