android - SoundManager 中偶尔出现 NullPointerException

Question

我使用这个标准的 SoundManager。它在我所有的设备上都能正常工作，但只是偶尔在市场上出现这些错误

1. SoundManager.playSound(SoundManager.java:87) 中的 NullPointerException

2. SoundManager.cleanup(SoundManager.java:107) 中的 NullPointerException

代码如下:

public class SoundManager {

    private static SoundManager _instance;
    private static SoundPool mSoundPool; 
    private static HashMap<Integer, Integer> mSoundPoolMap; 
    private static AudioManager  mAudioManager;
    private static Context mContext;

    private SoundManager(){   }

    static synchronized public SoundManager getInstance(){
        if (_instance == null) 
          _instance = new SoundManager();
        return _instance;
     }


    public static  void initSounds(Context theContext){ 
         mContext = theContext;
         mSoundPool = new SoundPool(4, AudioManager.STREAM_MUSIC, 0);
         mSoundPoolMap = new HashMap<Integer, Integer>(); 
         mAudioManager = (AudioManager)mContext.getSystemService(Context.AUDIO_SERVICE);        
    } 


    public static void addSound(int Index,int SoundID){
        mSoundPoolMap.put(Index, mSoundPool.load(mContext, SoundID, 1));
    }


    public static void loadSounds(){

        mSoundPoolMap.put(1, mSoundPool.load(mContext, R.raw.kick1, 1)); 
        mSoundPoolMap.put(2, mSoundPool.load(mContext, R.raw.kick2, 1)); 
        mSoundPoolMap.put(3, mSoundPool.load(mContext, R.raw.kick3, 1));    


    }


    public static void playSound(int index, float volume){      
             **line 87:** float streamVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC); 
             streamVolume = streamVolume / mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
             mSoundPool.play(mSoundPoolMap.get(index), streamVolume*volume, streamVolume*volume, 1, 0, 1); 
    }


    public static void stopSound(int index){
        mSoundPool.stop(mSoundPoolMap.get(index));
    }

    public static void cleanup(){
        **line 107:** mSoundPool.release();
        mSoundPool = null;
        mSoundPoolMap.clear();
        mAudioManager.unloadSoundEffects();
        _instance = null;

    }
}

这是启动 Activity 中的清理调用:

    //REMOVE SOUND MEMORY ALLOCATION
    @Override
    public void onDestroy()
        {
            super.onDestroy();
            SoundManager.cleanup();
        }

有谁知道是什么原因导致这些偶尔出现的罕见错误以及如何预防这些错误？这发生在我所有使用此 SoundManager 的应用程序中......即使是有点奇怪的猜测也会有所帮助。

Answer 1

当您初始化 SoundManager 时，请使用 Application Context。您可能在 Activity 之间移动时遇到问题。如果 SoundManager 比您的 Activity 生命周期更长。您甚至可以在您的应用程序中进行初始化。

public class MyAndroidApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        SoundManager.initSounds(this);
    }
}

我也同意 WarrenFaith 的观点。唯一的静态变量应该是 _instance 和 getInstance()。

此外，如果您在 Application 类中加载声音，则无需担心同步问题。

如果对您有帮助，您可以查看我使用的代码。它利用来自 http://code.google.com/p/opensl-soundpool/ 的 OpenSL SoundPool 库

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Random;
import java.util.concurrent.atomic.AtomicBoolean;

import android.content.Context;
import android.media.AudioManager;
import android.media.MediaPlayer;

import com.kytomaki.openslsoundpool.JavaSoundPool;
import com.kytomaki.openslsoundpool.OpenSLSoundPool;
import com.kytomaki.openslsoundpool.SoundPoolIf;

final public class SoundManager
{
    // Predetermined sound ID's
    public static final int             NO_SOUND        = -1 ;
    public static final int             WINNER          = -2 ;

    // Tag for logging
    protected static final String       TAG             = "SoundManager" ;

    /** Used to load and play sounds **/
    private Context                     context ;

    /** Sound can be disable from separate thread **/
    private final AtomicBoolean         useSound ;

    // Sound Arrays
    private final ArrayList<Integer>    winningSounds ;
    private final SoundPoolIf           soundPool ;
    private final HashMap<Integer, Integer> soundPoolMap ;
    private final AudioManager          audioManager ;

    /** Singleton object for sound play back **/
    private static SoundManager         soundManagerInstance ;


    private static final int            USE_SOUNDPOOL   = 1 ;
    private static final int            USE_OPENSL      = 2 ;
    private static int                  use             = USE_SOUNDPOOL ;



    /**
     * Private Method to create a new SoundManager<br>
     * This is a Singleton Object
     * @param context Should be the Application Context
     */
    private SoundManager( final Context context )
    {
        setContext( context ) ;
        useSound = new AtomicBoolean( true ) ;
        audioManager = (AudioManager) context.getSystemService( Context.AUDIO_SERVICE ) ;

        soundPoolMap = new HashMap<Integer, Integer>() ;
        winningSounds = new ArrayList<Integer>() ;

        if ( use == USE_OPENSL )
        {
            soundPool = new OpenSLSoundPool( 2, OpenSLSoundPool.RATE_44_1, OpenSLSoundPool.FORMAT_16, 1) ;
        } else {
            soundPool = new JavaSoundPool( 2 ) ;
        }
    }

    /**
     * Must be called before using<br>
     * Best to initialize in Application Class
     * @param context
     */
    public static void initSoundManager( final Context context )
    {
        if ( soundManagerInstance == null )
        {
            soundManagerInstance = new SoundManager( context ) ;
        }
        else
        {
            throw new UnsupportedOperationException( "Sound manager has already been created" ) ;
        }
    }

    /**
     * Overloaded method to allow use of OpenSL
     * @param context
     * @param useOpenSL
     */
    public static void initSoundManager( final Context context, final boolean useOpenSL){
        if(useOpenSL){
            use = USE_OPENSL;
        }
        initSoundManager(context);
    }

    /**
     * Must initialize first with {@link SoundManager#initSoundManager(Context)}
     * @return instance of SoundManager
     */
    public static SoundManager getSoundManagerInstance()
    {
        if ( soundManagerInstance != null )
        {
            return soundManagerInstance ;
        }
        else
        {
            throw new UnsupportedOperationException( "SoundManager must be initalized" ) ;
        }
    }


    /**
     * Add a sound from an android resource file R.id.sound<br>
     * To be played back with SoundManager.play(soundId)
     * @param soundId
     * @param soundResourceId
     */
    public void addSound( final int soundId, final int soundResourceId )
    {
        soundPoolMap.put(soundId, soundPool.load(getContext(), soundResourceId));
    }

    /**
     * Adds a winning sound from a resource to be played at random<br>
     * Called by SoundManager.play(WINNER)
     * @param soundResourceId
     */
    public void addWinningSound( final int soundResourceId )
    {
        winningSounds.add( soundResourceId ) ;
    }

    /**
     * Plays a sound first checking if sound is enabled
     * @param soundToPlay soundId or WINNER to play random winning sound
     */
    public synchronized void play( final int soundToPlay )
    {
        if ( isUseSound() )
        {
            switch ( soundToPlay )
            {
                case NO_SOUND :
                    break ;
                case WINNER :
                    // Play a random winning sound using media player
                    final MediaPlayer mp ;
                    mp = MediaPlayer.create( getContext(), randomWinnerSound() ) ; 
                    if ( mp != null )
                    {
                        mp.seekTo( 0 ) ;
                        mp.start() ;
                    }
                    break ;
                default :
                    playSound( soundToPlay ) ;
                    break ;
            }
        }
    }

    /**
     * Calls soundpool.play
     * @param soundToPlay
     */
    private void playSound( final int soundToPlay )
    {
        float streamVolume = audioManager.getStreamVolume( AudioManager.STREAM_MUSIC ) ;
        streamVolume = streamVolume / audioManager.getStreamMaxVolume( AudioManager.STREAM_MUSIC ) ;
        soundPool.play(soundPoolMap.get(soundToPlay), streamVolume);
    }

    /**
     * @return random winning sound position
     */
    private int randomWinnerSound()
    {
        final Random rand = new Random() ;
        final int playNumber = rand.nextInt( winningSounds.size() ) ;
        return winningSounds.get( playNumber ) ;
    }

    /**
     * @param context the context to set
     */
    private final void setContext( final Context context )
    {
        this.context = context ;
    }

    /**
     * @return the context
     */
    private final Context getContext()
    {
        return context ;
    }

    /**
     * @param useSound false to disable sound
     */
    public final void setUseSound( final boolean useSound )
    {
        this.useSound.set( useSound ) ;
    }

    /**
     * @return the useSound
     */
    public boolean isUseSound()
    {
        return useSound.get() ;
    }


}

仍在进行中，但已完成工作。