android - 应用程序在 mp.setDataSource(this, path) 处崩溃；

Question

我是 Android 开发新手。我正在尝试根据位置选择歌曲时播放歌曲。它总是崩溃并且有多个错误。我真的不明白我做错了什么。可能是愚蠢的错误，请帮助。

public class BackgroundAudioService extends Service implements MediaPlayer.OnCompletionListener, MediaPlayer.OnPreparedListener{

    MediaPlayer mp;
    int mainpositionno;
    int itempositionno;
    int i;
    Uri path;
    Intent playbackServiceIntent;

    BackgroundAudioService instanceService;
    public BackgroundAudioService() {
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        mp = new MediaPlayer();
        mp.start();
    }

    class LocalBinder extends Binder{
        public BackgroundAudioService getService(){
            return instanceService;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        int mainpositionno = intent.getIntExtra("Mainpositionno", 0);
        int itempositionno = intent.getIntExtra("Itempositionno", 0);
        this.mainpositionno = mainpositionno;
        this.itempositionno = itempositionno;
        setSongAtPosition(mainpositionno,itempositionno);
        return new LocalBinder();
    }

    public void setSongAtPosition(int mainposition, int position){
        mainpositionno = mainposition;
        itempositionno = position;
        //String filePath = "somepath/somefile.mp3";
        Uri path = null;
        Toast.makeText(BackgroundAudioService.this,"main "+mainposition+ " pos"+position,Toast.LENGTH_SHORT).show();

        if (mainpositionno == 0){
            switch (itempositionno){
                case 0:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.namah_shivaya_chanting);
                    break;
                }
                case 1:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.om_namasivaya);
                    break;
                }
                case 2:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.sivamayamana);
                    break;
                }
            }
        }else
        if (mainpositionno == 1) {
            switch (itempositionno){
                case 0:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.om_namo_narayanaya);
                    break;
                }
                case 1:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.suprabhatham);
                    break;
                }
            }
        }else
        if (mainpositionno == 2) {
            switch (itempositionno) {
                case 0: {
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.saranamiyyapa_chanting);
                    break;
                }
                case 1: {
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.harivarasanam);
                    break;
                }
                case 2: {
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.pallikattu_sabarimalaiku);
                    break;
                }
            }
        }else
        if (mainpositionno == 3) {
            switch (itempositionno){
                case 0:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.kandha_guru_kavasam);
                    break;
                }
                case 1:{
                    path = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.kandha_sasti_kavasam);
                    break;
                }
            }
        }else
        if (mainpositionno == 4) {
            //To set
        }
        if(mp.isPlaying()) mp.stop(); mp.reset();
        mp = MediaPlayer.create(BackgroundAudioService.this, path);
        mp.setOnCompletionListener(this);
        try {
            mp.setDataSource(this, path);
        } catch (IOException e) {
            e.printStackTrace();
        }
        mp.setOnPreparedListener(this);
        mp.prepareAsync();
    }

    @Override
    public void onCreate() {
        instanceService = this;
        mp = new MediaPlayer();
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    @Override
    public void onCompletion(MediaPlayer mp) {
    }

}

08-17 10:12:11.767    6290-6290/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 6290
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.setOnCompletionListener(android.media.MediaPlayer$OnCompletionListener)' on a null object reference

08-17 10:13:15.827 7386-7386/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 7386
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.setOnCompletionListener(android.media.MediaPlayer$OnCompletionListener)' on a null object reference

08-17 10:13:23.644    7797-7797/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 7797
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.setOnCompletionListener(android.media.MediaPlayer$OnCompletionListener)' on a null object reference

08-17 12:54:09.221    5223-5223/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 5223
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.setOnCompletionListener(android.media.MediaPlayer$OnCompletionListener)' on a null object reference

08-17 12:54:21.419    5366-5366/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 5366
    java.lang.RuntimeException: Unable to bind to service com.fishy.meena.hindudevotionalsongs.BackgroundAudioService@25561ca2 with Intent { cmp=com.fishy.meena.hindudevotionalsongs/.BackgroundAudioService (has extras) }: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.media.MediaPlayer.isPlaying()' on a null object reference

08-18 08:41:40.568  31629-31629/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 31629
    java.lang.RuntimeException: Unable to bind to service com.fishy.meena.hindudevotionalsongs.BackgroundAudioService@3ff5f51d with Intent { cmp=com.fishy.meena.hindudevotionalsongs/.BackgroundAudioService (has extras) }: java.lang.IllegalStateException

08-18 08:42:16.058  32172-32172/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.fishy.meena.hindudevotionalsongs, PID: 32172
    java.lang.RuntimeException: Unable to bind to service com.fishy.meena.hindudevotionalsongs.BackgroundAudioService@1dd66392 with Intent { cmp=com.fishy.meena.hindudevotionalsongs/.BackgroundAudioService (has extras) }: java.lang.IllegalStateException

Answer 1

为了确定，只需检查:

<强>1。 mp 对象不为空

<强>2。 URI 有效