然而现在它似乎被打破了……

程序启动后,在初始化后,代码进入以下方法并成功运行：

public void discoverServices() {
    Log.d(TAG,"Initializing discovery on NSD");
    mNsdManager.discoverServices(
            SERVICE_TYPE,NsdManager.PROTOCOL_DNS_SD,mDiscoveryListener);
}

收到日志消息.经过一段时间(约5分钟),这是从程序输出：

05-21 11:08:32.518: E/NsdCamera(12236): Discovery Failed: Error code:0
05-21 11:08:32.518: W/dalvikvm(12236): threadid=12: thread exiting with uncaught exception (group=0x40c9c930)
05-21 11:08:32.518: E/AndroidRuntime(12236): FATAL EXCEPTION: NsdManager
05-21 11:08:32.518: E/AndroidRuntime(12236): java.lang.NullPointerException
05-21 11:08:32.518: E/AndroidRuntime(12236):    at android.net.nsd.NsdManager$ServiceHandler.handleMessage(NsdManager.java:338)
05-21 11:08:32.518: E/AndroidRuntime(12236):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-21 11:08:32.518: E/AndroidRuntime(12236):    at android.os.Looper.loop(Looper.java:137)
05-21 11:08:32.518: E/AndroidRuntime(12236):    at android.os.HandlerThread.run(HandlerThread.java:60)

还来自服务：

05-21 11:50:49.108: E/NativeDaemonConnector.ResponseQueue(8858): Timeout waiting for response
05-21 11:50:49.108: E/mDnsConnector(8858): timed-out waiting for response to 10 mdnssd discover 6 _http._tcp.
05-21 11:50:49.108: E/NsdService(8858): Failed to discoverServices com.android.server.NativeDaemonConnector$NativeDaemonFailureException: command '10 mdnssd discover 6 _http._tcp.' Failed with 'null'

错误代码“0”在NSDManager class中描述为内部错误.
我做的主要更新是访问名为NsdCamera的helper类中的上下文.
这里有一些可能是邪恶的代码片段：

助手级构造函数：

public NsdCamera(CameraChooseActivity context) {
    mContext = context;
    updateUI =  new UpdateUI();
    mNsdManager = (NsdManager) context.getSystemService(Context.NSD_SERVICE);
    mServiceName = new Vector<NsdServiceInfo>();

Helper级NSD初始化：

public void initializeNsd() {
    initializeDiscoveryListener();
}

public void initializeDiscoveryListener() {
    mDiscoveryListener = new NsdManager.DiscoveryListener() {

        @Override
        public void onDiscoveryStarted(String regType) {
            Log.d(TAG,"Service discovery started");
        }
        /**
         * A name check to see if the DNS discovery was correct. Checks if it contains 
         * AXIS and has the desired MAC address-space
         * @param hostname,the inputted hostname from the discovery cycle
         * @return true if it's an Axis camera. 
         */
        public boolean nameCheck(String hostname){
            return (hostname.contains("AXIS") && hostname.contains("00408C"));

        }
        @Override
        public void onServiceFound(NsdServiceInfo service) {
            Log.d(TAG,"Service discovery success: " + service.getServiceName());
            if (!service.getServiceType().equals(SERVICE_TYPE)) {
                Log.d(TAG,"Unknown Service Type: " + service.getServiceType());
            } else if (nameCheck(service.getServiceName())){
                mServiceName.add(service);
//                  updateUI.execute(new BundleUI(mContext,service,null));
            }
        }

        @Override
        public void onServiceLost(NsdServiceInfo service) {
            Log.e(TAG,"service lost" + service);
            if(mServiceName.remove(service)){
                //TODO
                Log.e(TAG,"remove the view,service is lost");
            }
        }

        @Override
        public void onDiscoveryStopped(String serviceType) {
            Log.i(TAG,"Discovery stopped: " + serviceType);
            //Necessary??
            mServiceName.clear();
        }

        @Override
        public void onStartDiscoveryFailed(String serviceType,int errorCode) {
            Log.e(TAG,"Discovery Failed: Error code:" + errorCode);
            mNsdManager.stopServiceDiscovery(this);
        }

        @Override
        public void onStopDiscoveryFailed(String serviceType,"Discovery Failed: Error code:" + errorCode);
            mNsdManager.stopServiceDiscovery(this);
        }
    };
}

CameraChooseActivity – > onCreate正在调用helper-class

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_camerachoose);

    //Setup the animation for the text in the Relativelayout
    mDescription = (TextSwitcher) findViewById(R.id.camera_add);
    mDescription.setFactory(this);
    mDescription.setInAnimation(AnimationUtils.loadAnimation(this,android.R.anim.fade_in));
    mDescription.setOutAnimation(AnimationUtils.loadAnimation(this,android.R.anim.fade_out));
    mDescription.setText(getText(R.string.camera_add));

    //Building alert dialog
    mBuilder = new AlertDialog.Builder(this,AlertDialog.THEME_HOLO_DARK);
    mBuilder.setMessage(R.string.dialog_about).setTitle(R.string.action_about);
    mBuilder.setIcon(android.R.drawable.ic_dialog_info);

    mLayout = (RelativeLayout) findViewById(R.id.layout_camerachoose);

    //Initialize the NSD
    mNSDHelper = new NsdCamera(this);
    mNSDHelper.initializeNsd();