這裏有什麼問題，我不能綁定服務在android

Question

它是返回NullPointerException當我點擊播放按鈕，我想要停止按鈕與getCount（）方法在Service類中的值應該返回1 ，當我點擊播放按鈕時它會崩潰。 這是活動類：

public class MainMP3 extends Activity{ 
Button stop; 
static final String MEDIA_PATH = new String("/sdcard/"); 
Button data_display; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.mp3interface); 
    startService(new Intent(MainMP3.this, ServiceMP3.class)); 

    stop= (Button) findViewById(R.id.stop); 

    // to stop service 
    //stopService(new Intent(MainMP3.this, ServiceMP3.class)); 

    Button button = (Button)findViewById(R.id.play); 
    button.setOnClickListener(new StartClick()); 

} 

    private ServiceMP3 service = null; 

    private ServiceConnection connection = new ServiceConnection() { 
     @Override // Called when connection is made 
     public void onServiceConnected(ComponentName cName, IBinder binder) { 
      service = ((ServiceMP3.SlowBinder)binder).getService(); 
     } 
     @Override // 
     public void onServiceDisconnected(ComponentName cName) { 
      service = null; 
     } 
    }; 

    private class StartClick implements View.OnClickListener {  
     public void onClick(View v) { 
      int data = service.getCount(); 
      stop.setText(Integer.toString(data)); 
     } 
    } 
     } 

這裏是服務：

public class ServiceMP3 extends Service { 

private static final String MEDIA_PATH = new String("/sdcard/"); 
private MediaPlayer mp = new MediaPlayer(); 
private List<String> songs = new ArrayList<String>(); 
private int currentPosition; 
int count=1; 
private NotificationManager nm; 
private static final int NOTIFY_ID = R.layout.song; 


    public int getCount() {return count;} 

    @Override 
    public void onCreate() { 
     super.onCreate(); 
     BindAllSongs(); 

     System.out.println(MEDIA_PATH+ songs.get(currentPosition)); 

     for (int i = 0; i < songs.size(); i++) { 
      System.out.println(songs.get(i).toString()); 
     } 

     nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE); 

      //   playSong(MEDIA_PATH+ songs.get(currentPosition)); 

      //   Thread thr = new Thread(null, work, "Play Song"); 
      //   thr.start(); 

      // Toast.makeText(this, "Service Started", Toast.LENGTH_SHORT).show(); 
      //   player = MediaPlayer.create(ServiceMP3.this, R.raw.test); 
      //   player.start(); 
      //   player.setLooping(true); 
    } 

    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) { 

     Toast.makeText(this, "Service started...", Toast.LENGTH_LONG).show(); 
     return Service.START_NOT_STICKY; 
    } 



    @Override 
    public void onDestroy() { 
     super.onDestroy(); 
     mp.stop(); 
     mp.release(); 
     nm.cancel(NOTIFY_ID); 
     Toast.makeText(this, "Service Stopped", Toast.LENGTH_SHORT).show(); 
    } 


    public void BindAllSongs() 
    { 
     // TODO Auto-generated method stub 

     //To hold all the audio files from SDCARD 
     File fileListBeforeFiltering = new File(MEDIA_PATH); 
     //Filter all the MP# format songs to list out 
     //Checking for the MP3 Extension files existence 
      if (fileListBeforeFiltering.listFiles(new FilterFilesByMp3Extension()).length > 0) 
      { 
       //Loop thru all the files filtered and fill them in SongsList view that we have 
       //Defined above. 
       for (File file : fileListBeforeFiltering.listFiles(new FilterFilesByMp3Extension())) 
       { 
        //Adding all filtered songs to the list 
         songs.add(file.getName()); 
       } 

     } 
    } 

    void playSong(String file) { 
     try { 





       mp.setDataSource(file); 

       mp.prepare(); 
       mp.start(); 

       mp.setOnCompletionListener(new OnCompletionListener() { 

        public void onCompletion(MediaPlayer arg0) { 
          nextSong(); 
        } 
      }); 

     } catch (IOException e) { 
       Log.e(getString(R.string.app_name), e.getMessage()); 
     } 
     } 


    void nextSong() { 
     // Check if last song or not 
     if (++currentPosition >= songs.size()) { 
       currentPosition = 0; 
       nm.cancel(NOTIFY_ID); 
     } else { 
       playSong(MainMP3.MEDIA_PATH + songs.get(currentPosition)); 
     } 


} 

    void prevSong() { 
     if (mp.getCurrentPosition() < 3000 && currentPosition >= 1) { 
       playSong(MainMP3.MEDIA_PATH + songs.get(--currentPosition)); 
     } else { 
       playSong(MainMP3.MEDIA_PATH + songs.get(currentPosition)); 
     } 
} 


    Runnable work = new Runnable() { 
     public void run() { 

      while (true) { 

       System.out.println("Runnable method...."); 

      } 

     } 

    }; 


    private final IBinder binder = new SlowBinder(); 

    @Override 
    public IBinder onBind(Intent intent) { 
     return binder; 
    } 

    public class SlowBinder extends Binder { 
     ServiceMP3 getService() { 
      return ServiceMP3.this; 
     } 
    } 


} 

Answer 1

首先嚐試更換

startService（新意圖（MainMP3.this，ServiceMP3.class）） ;

上

bindService（新意圖（MainMP3.this，ServiceMP3.class））;

閱讀請：Bound Services