java - 无法访问在 try/catch 语句中初始化的变量

Question

我正在为我的游戏制作一个声音类，经过多次尝试，我似乎无法摆脱 NullPointerException。发生这种情况是因为我无法访问 try/catch 语句中的变量。

这是代码:

package util;

import java.applet.*;
import java.net.URL;

public class Sound 
{
    private AudioClip audio;
    private URL file;

    public Sound(String srcfile)
    {
        try 
        {
            this.file = new URL(srcfile);
        } 
        catch(Exception e){}

        this.audio = Applet.newAudioClip(file);
    }

    public void Play()
    {
        this.audio.play();
    }

    public void Loop()
    {
        this.audio.loop();
    }

    public void Stop()
    {
        this.audio.stop();
    }

    public AudioClip getAudio() 
    {
        return audio;
    }

    public void setAudio(AudioClip audio) 
    {
        this.audio = audio;
    }
}

这是错误(不再出现):

Exception in thread "main" java.lang.NullPointerException
    at sun.applet.AppletAudioClip.<init>(Unknown Source)
    at java.applet.Applet.newAudioClip(Unknown Source)
    at util.Sound.<init>(Sound.java:19)
    at main.Blocks.run(Blocks.java:38)
    at main.Blocks.main(Blocks.java:26)

修改旧代码后，她就是新代码:

package util;

import java.applet.*;
import java.net.URL;

public class Sound 
{
    private AudioClip audio;

    public Sound(String srcfile)
    {
        try 
        {
            this.audio = Applet.newAudioClip(new URL("file://" + srcfile));
        } 
        catch(Exception e)
        {
            Log.log(e.getMessage(), Log.ERROR);
            e.printStackTrace();
            System.exit(1);
        }
    }

    public void Play()
    {
        this.audio.play();
    }

    public void Loop()
    {
        this.audio.loop();
    }

    public void Stop()
    {
        this.audio.stop();
    }

    public AudioClip getAudio() 
    {
        return audio;
    }

    public void setAudio(AudioClip audio) 
    {
        this.audio = audio;
    }
}

我正在打电话 玩();但什么也没发生

这是我调用该方法的方式:

Sound snd = new Sound("res/dev/sound.wav");
snd.Play();

如有任何帮助，我们将不胜感激。

Answer 1

从类的设计方式来看，似乎不需要 file 变量存在于构造函数之外。像这样的东西可能会很好用:

public Sound(String srcfile) {
        try {
            this.audio = Applet.newAudioClip(new URL(srcfile));
        } 
        catch(Exception e){
             //at least print the stack trace
             e.printStackTrace();
             //do some proper exception handling that makes sense for you app!
        }
}