intentService resultReceiver nullpointerException

Question

我在IntentService类上实现ResultReceiver时遇到了困难，该类会扫描网络上的可用设备。 （到目前为止无视我的代码的可怕设计）我似乎甚至不能让我的resultReceiver传回一个测试字符串，日志会选择我发送的实例，但是我得到一个nullPointerException我尝试访问传入的字符串。

以下是我的Intent Service类的相关部分：

public class NetHelper extends IntentService{

private ConnectivityManager cm;
private WifiManager manager;
private WifiInfo connectionInfo;
private NetworkInfo activeNetwork;


public Context myContext;
public ResultReceiver receiver;
public Bundle b;


SharedPreferences netprefs;
SharedPreferences.Editor editor;


@Override
protected void onHandleIntent(@Nullable Intent intent) {

    //if intent-int == 0: run netsniff
    //if intent-int == 1: run getNetInfo
    int OPR = intent.getIntExtra("OPR", 0); //0 is default value...

    //result receiver for callback use
    Bundle params = intent.getExtras();
    receiver = params.getParcelable("receiverTag");
    b = new Bundle();

    //long running operation is netsniff
    listDevices = new ArrayList<Devices>();
    myContext = getApplicationContext();


    //application based storing of values
    netprefs = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE);
    editor = netprefs.edit();

    cm = (ConnectivityManager) myContext.getSystemService(Context.CONNECTIVITY_SERVICE);
    activeNetwork = cm.getActiveNetworkInfo();
    manager = (WifiManager) myContext.getSystemService(Context.WIFI_SERVICE);
    connectionInfo = manager.getConnectionInfo();

    if (OPR == 0) {
        try {
            netSniff();

        } catch (IOException e) {
            e.printStackTrace();
            Log.d(TAG, e.toString());
        }
    }
}

我的函数中的

片段发送了一个新的包：

    public void netSniff() throws IOException {
    Log.d(TAG, "begin sniffing network on network: "+ NET_IP);
    Log.d(TAG, "Active Network: " + String.valueOf(activeNetwork));
    Log.d(TAG, "IP_ADDR: " + String.valueOf(MYNET_IP));


    b.putString("RESULT_RECEIVED", "TESTING23748W3458763298457Y34");
    receiver.send(0, b);

myResultReceiver类：

public class myResultReceiver extends ResultReceiver{
private Receiver mReceiver;


public myResultReceiver(Handler handler) {
    super(handler);
}


public interface Receiver {
    public void onReceiveResult(int resultCode, Bundle resultData);

}

public void setReceiver(Receiver receiver) {
    mReceiver = receiver;
}

@Override
protected void onReceiveResult(int resultCode, Bundle resultData) {

    if (mReceiver != null) {
        mReceiver.onReceiveResult(resultCode, resultData);
    }
}

最后，这是我对片段的要求：

public class devicesFragment extends Fragment implements myResultReceiver.Receiver {
public myResultReceiver mReceiver;



   //discover network info, and get a list of devices
public void launchNetworkSniffer(int opr) {
    Intent serviceIntent = new Intent(getActivity(), NetHelper.class);

    //setup resultReceiver for service callbacks
    mReceiver = new myResultReceiver(new Handler());
    mReceiver.setReceiver(this);

    serviceIntent.putExtra("receiverTag", mReceiver);
    serviceIntent.putExtra("OPR", opr);
    getActivity().startService(serviceIntent);
}

    //receiver implemented methods
@Override
public void onReceiveResult(int resultCode, Bundle resultData) {
    Log.d("DATA_RECEIVED******", "processing...");
    String newdevjson = resultData.getString("RECEIVED_RESULT");
    Log.d("DATA_RECEIVED", newdevjson);
    Devices newd = new Gson().fromJson(newdevjson, Devices.class);
    devlist.add(newd);

    for (Devices i : devlist) {
        Log.d("ACTIVE_DEV_COUNT", i.getIp());
    }
}

我的片段onResultReceived()中的第一个日志正在显示，但是当我为resultData.getString()分配nullPointerReference时，它会崩溃。

我相信这个事实意味着我已经正确地实例化了一切，所以为什么根本没有传回任何东西？