允许Java应用程序在录制音频时继续运行

Question

I am trying to embed some code I found (original here ) for recording and saving audio input into a Java swing application. My problem is that I want the audio recording to run concurrently with other things the application is doing, but in fact, the application pauses until the audio recording is finished. How can I prevent this from happening?

Here's a simplified version of my code that produces the issue. The line that displays "Now recording" does not appear until after the audio recording is finished.

import javax.sound.sampled.*;

import java.io.*;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.io.File;

import javafx.embed.swing.JFXPanel;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Example extends JPanel {

    protected static final long serialVersionUID = 1L;

    // whether we've started recording
    private boolean startedRecording;

    // record duration, in milliseconds
    static final long RECORD_TIME = 5000;  // 5 seconds

    // format of audio file
    AudioFileFormat.Type fileType = AudioFileFormat.Type.WAVE;

    // path of the wav file
    File wavFile;

    // the line from which audio data is captured
    TargetDataLine line;

    public Example( String output_fn ) {
        wavFile = new File(output_fn);
        startedRecording = false;
        setPreferredSize(new Dimension(100,100));
        createPanel();
    }

    public static JFXPanel createPanel() {
        return new JFXPanel();
    }

    /**
     * Defines an audio format
     */
    AudioFormat getAudioFormat() {
        float sampleRate = 16000;
        int sampleSizeInBits = 8;
        int channels = 2;
        boolean signed = true;
        boolean bigEndian = true;
        AudioFormat format = new AudioFormat(sampleRate, sampleSizeInBits,
                                             channels, signed, bigEndian);
        return format;
    }

    /**
     * Captures the sound and record into a WAV file
     */
    public void start() {
        try {
            AudioFormat format = getAudioFormat();
            DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);

            // checks if system supports the data line
            if (!AudioSystem.isLineSupported(info)) {
                System.out.println("Line not supported");
                System.exit(0);
            }
            line = (TargetDataLine) AudioSystem.getLine(info);
            line.open(format);
            line.start();   // start capturing

            System.out.println("In utils.Recorder: Start capturing...");

            AudioInputStream ais = new AudioInputStream(line);

            System.out.println("In utils.Recorder: Start recording...");

            // start recording
            AudioSystem.write(ais, fileType, wavFile);

        } catch (LineUnavailableException ex) {
            ex.printStackTrace();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
        repaint();
    }

    /**
     * Closes the target data line to finish capturing and recording
     */
    public void finish() {
        line.stop();
        line.close();
        System.out.println("In utils.Recorder: Finished");
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2   = (Graphics2D)g;
        // start recording
        if ( !startedRecording ) {
            startedRecording = true;
            Thread stopper = new Thread(new Runnable() {
                public void run() {
                    try {
                        Thread.sleep(RECORD_TIME);
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
                    }
                    Example.this.finish();
                }
            });
            stopper.start();
            this.start();
        }
        // display message
        g2.drawString("Now recording", 50, 50);
    }

    public static void main(String[] args) {
        final Example eg = new Example("TestRecordAudio.wav");
        JFrame f    = new JFrame();
        f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        f.add(eg, BorderLayout.CENTER);
        f.pack();
        f.setVisible(true);
        f.repaint();
    }
}

Answer 1

Paint methods are for painting! Never perform any other actions within the paint method, it's simply inappropriate and a really, really bad idea.

Create a JButton (or JToggleButton ) and use this to start/stop the recording.

Use line.stop() and line.close() to stop the recording.

Swing is a single thread environment, any long running or blocking code which is executed within the context of the Event Dispatching Thread will prevent it from processing the Event Queue, making it look like your program has hung, because it has.

You could use a SwingWorker , but since you're not trying to update the UI while you're recording, it would be easier to use a Thread

Take a look at

• Concurrency in Swing
• How to Use Buttons, Check Boxes, and Radio Buttons
• How to Write an Action Listeners

for more details

Updated with example

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;
import javax.sound.sampled.AudioFileFormat;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.TargetDataLine;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JToggleButton;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestRecord {

    public static void main(String[] args) {
        new TestRecord();
    }

    public TestRecord() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public static class TestPane extends JPanel {

        private JToggleButton recordButton;

        protected static final AudioFileFormat.Type FILE_TYPE = AudioFileFormat.Type.WAVE;
        private TargetDataLine line;

        public TestPane() {
            setLayout(new GridBagLayout());
            recordButton = new JToggleButton("Record");
            recordButton.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    if (recordButton.isSelected()) {
                        startRecording();
                        recordButton.setText("Stop");
                    } else {
                        stopRecording();
                        recordButton.setText("Record");
                    }
                }
            });
            add(recordButton);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void stopRecording() {

            if (line != null) {

                line.stop();
                line.close();
                line = null;

            }

        }

        protected void startRecording() {
            if (line == null) {
                Thread t = new Thread(new Runnable() {

                    @Override
                    public void run() {
                        try {
                            AudioFormat format = getAudioFormat();
                            DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);

                            // checks if system supports the data line
                            if (!AudioSystem.isLineSupported(info)) {
                                System.out.println("Line not supported");
                                System.exit(0);
                            }
                            line = (TargetDataLine) AudioSystem.getLine(info);
                            line.open(format);
                            line.start();   // start capturing

                            System.out.println("In utils.Recorder: Start capturing...");

                            AudioInputStream ais = new AudioInputStream(line);

                            System.out.println("In utils.Recorder: Start recording...");

                            // start recording
                            System.out.println("Is recoding");
                            AudioSystem.write(ais, FILE_TYPE, new File("Test.wav"));

                        } catch (LineUnavailableException ex) {
                            ex.printStackTrace();
                        } catch (IOException ioe) {
                            ioe.printStackTrace();
                        }

                        System.out.println("Recording is done");
                    }
                });
                t.start();
            }
        }

        protected AudioFormat getAudioFormat() {
            float sampleRate = 16000;
            int sampleSizeInBits = 8;
            int channels = 2;
            boolean signed = true;
            boolean bigEndian = true;
            AudioFormat format = new AudioFormat(sampleRate, sampleSizeInBits,
                            channels, signed, bigEndian);
            return format;
        }
    }

}

(nb: I've not been able to test it, as I don't have a line available to support recording...apparently)

Answer 2

You're calling start on the AWT Event Dispatch Thread thus blocking anything else from happening. You need to call your audio calling code on a different thread.

You should never run long running tasks on the Swing thread unless you want to face the grey screen of death