與多個活動綁定服務

Question

我想綁定多個活動服務，所以我寫了一個應用程序類來管理這個目標：

public class BluetoothController extends Application { 
    private static BluetoothController mInstance; 
    private ClientBluetoothService mService; 
    protected boolean mBound = false; 

    public static synchronized BluetoothController getInstance() { 
     return mInstance; 
    } 

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

    public void startService(){ 
     //start your service 
     Intent intent = new Intent(this, ClientBluetoothService.class); 
     bindService(intent, mConnection, Context.BIND_AUTO_CREATE); 
    } 
    public void stopService(){ 
     //stop service 
     if (mBound) { 
      unbindService(mConnection); 
      mBound = false; 
     } 
    } 

    public ClientBluetoothService getService(){ 
     return mService; 
    } 

    public boolean isBound() { 
     return mBound; 
    } 

    private ServiceConnection mConnection = new ServiceConnection() { 

     @Override 
     public void onServiceConnected(ComponentName className, IBinder service) { 

      ClientBluetoothService.LocalBinder binder = (ClientBluetoothService.LocalBinder) service; 
      mService = binder.getSerivce(); 
      mBound = true; 
     } 

     @Override 
     public void onServiceDisconnected(ComponentName arg0) { 
      mBound = false; 
     } 
    }; 
} 

並訪問這個類在我使用例如活動：

BluetoothController.getInstance().startService(); 

但是我有一個錯誤：顯示java.lang.NullPointerException：嘗試調用虛擬方法「無效com.gmail.krakow.michalt.myecg.BluetoothController.startService（）」上的空對象引用。 如何解決？

Answer 1

public static synchronized BluetoothController getInstance() { 
    return mInstance = new BluetoothController(); 
}