Question

    package sounds;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.util.HashMap;
import javax.sound.sampled.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class Playlist
{

    private Clip activeClip;

    /**
     * Creates an audio clip from a sound file.
     */
    public Clip createClip (String soundFile)
    {
        String fileName = "/sounds/" + soundFile + ".wav";
        try (BufferedInputStream sound = new BufferedInputStream(getClass().getResourceAsStream(fileName)))
        {
            // Create and return a Clip that will play a sound file. There are
            // various reasons that the creation attempt could fail. If it
            // fails, return null.
            Clip clip = AudioSystem.getClip();
            clip.open(AudioSystem.getAudioInputStream(sound));
            return clip;
        }
        catch (LineUnavailableException e)
        {
            return null;
        }
        catch (IOException e)
        {
            return null;
        }
        catch (UnsupportedAudioFileException e)
        {
            return null;
        }
    }

    public void play (String sound)
    {
        Clip clip = createClip(sound);
        if (clip != null)
        {
            if (clip.isRunning())
            {
                clip.stop();
            }
            clip.setFramePosition(0);
            clip.start();
        }
    }

    public void startLoop (String sound)
    {
        Clip clip = createClip(sound);
        if (clip != null)
        {
            if (clip.isRunning())
            {
                clip.stop();
            }
                clip.setFramePosition(0);
                clip.loop(Clip.LOOP_CONTINUOUSLY);
                activeClip = clip;
        }
    }

    public void stopLoop ()
    {
        if (activeClip != null) {
          if (activeClip.isRunning()) {
            activeClip.stop();
          }
        }
    }

}

所以我的主要问题是循环。当我有一个对象以一个音频文件开始循环时，它开始并停止正常，但是当我有两个对象同时调用startLoop时，只有最近的一个会停止而另一个将继续运行。我已经考虑过将每个带有名称的剪辑放入HashMap中，这样我就可以按名称区分每个剪辑但不断得到NullPointerException错误，而不管我如何将其“放入”Map中

这是我尝试将其放入HashMap的版本。基本相似的代码，但每次调用play或startloop时，字符串都充当键并存储剪辑，以便稍后可以检索它以停止循环。但是每次我这样做，我都会在线上得到NullPointerException：我试图把它放到Map中：

    package sounds;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.util.HashMap;
import javax.sound.sampled.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class Playlist
{

    //private Clip activeClip;

    //Here
    private HashMap<String, Clip> list;

    /**
     * Creates an audio clip from a sound file.
     */
    public Clip createClip (String soundFile)
    {
        String fileName = "/sounds/" + soundFile + ".wav";
        // Opening the sound file this way will work no matter how the
        // project is exported. The only restriction is that the
        // sound files must be stored in a package.
        try (BufferedInputStream sound = new BufferedInputStream(getClass().getResourceAsStream(fileName)))
        {
            Clip clip = AudioSystem.getClip();
            clip.open(AudioSystem.getAudioInputStream(sound));
            return clip;
        }
        catch (LineUnavailableException e)
        {
            return null;
        }
        catch (IOException e)
        {
            return null;
        }
        catch (UnsupportedAudioFileException e)
        {
            return null;
        }
    }

    public void play (String sound)
    {
        Clip clip = createClip(sound);
        //Here
        list.put(sound, clip);
        if (clip != null)
        {
            if (clip.isRunning())
            {
                clip.stop();
            }
            clip.setFramePosition(0);
            clip.start();
        }
    }

    public void startLoop (String sound)
    {
        Clip clip = createClip(sound);
        //Here
        list.put(soundFile, clip);
        if (clip != null)
        {
            if (clip.isRunning())
            {
                clip.stop();
            }
                clip.setFramePosition(0);
                clip.loop(Clip.LOOP_CONTINUOUSLY);
        }
    }

    public void stopLoop (String sound)
    {
        //Here
        Clip clip = (Clip) list.get(sound);
        if (clip != null) {
          if (clip.isRunning()) {
            clip.stop();
          }
        }
    }

}

Answer 1

您没有实例化名为“list”的HashMap。

private HashMap<String, Clip> list = new HashMap<>();

Java如何阻止多个音频循环播放

1 个答案: