过渡到新片段的上下文中的错误

Question

在操作期间AsyncTask我在AsyncTask完成之前去新片之前我去了一个新片段，我看到与Context相关的错误。

例如： 我在包含列表的片段上。运行我的AsyncTask并立即转到另一个片段。我看到一个错误：

12-24 03:03:50.678    1516-1516/com.managment.pavel.managmentgradle E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at android.view.LayoutInflater.from(LayoutInflater.java:171)
            at com.managment.pavel.managmentgradle.fragments.adapters.GuestsListAdapter.<init>(GuestsListAdapter.java:40)
            at com.managment.pavel.managmentgradle.fragments.GuestsList$1.onPostExecute(GuestsList.java:141)
            at com.managment.pavel.managmentgradle.fragments.GuestsList$1.onPostExecute(GuestsList.java:91)
            at android.os.AsyncTask.finish(AsyncTask.java:417)
            at android.os.AsyncTask.access$300(AsyncTask.java:127)
            at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:130)
            at android.app.ActivityThread.main(ActivityThread.java:3683)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:507)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
            at dalvik.system.NativeStart.main(Native Method)

错误就行：

   inflater = LayoutInflater.from(ctx);

完整代码适配器：

public class GuestsListAdapter extends BaseAdapter implements View.OnClickListener {

    private LayoutInflater inflater;
    private ArrayList<GuestBean> guests;
    private Context ctx;
    private DisplayImageOptions options;
    private ImageLoadingListener animateFirstListener = new AnimateFirstDisplayListener();

    public GuestsListAdapter(Context ctx, ArrayList<GuestBean> guests) {
        this.guests = guests;
        this.ctx = ctx;
        inflater = LayoutInflater.from(ctx);
        options = ILOptions.getOption();
    }

    @Override
    public int getCount() {
        return guests.size();
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {

        View view = convertView;
        final ViewHolder holder;

        if (convertView == null) {
            view = inflater.inflate(R.layout.itemguest, parent, false);
            holder = new ViewHolder();
            holder.number = (TextView) view.findViewById(R.id.roomNumber);
            holder.name = (TextView) view.findViewById(R.id.guestName);
            holder.image = (CircleImageView) view.findViewById(R.id.imageView);
            holder.balance = (TextView) view.findViewById(R.id.guestBalance);
            holder.company = (TextView) view.findViewById(R.id.guestСompany);
            holder.night = (TextView) view.findViewById(R.id.guestNight);
            holder.wifi = (ImageView) view.findViewById(R.id.wifiImg);
            holder.inroom = (ImageView) view.findViewById(R.id.inroomImg);
            holder.cleaning = (ImageView) view.findViewById(R.id.cleaningImg);
            holder.tv = (ImageView) view.findViewById(R.id.tvImg);
            holder.checkin = (TextView) view.findViewById(R.id.checkinText);
            holder.tarif = (TextView) view.findViewById(R.id.tarifText);
            view.setTag(holder);
        } else {
            holder = (ViewHolder) view.getTag();
        }
        holder.number.setText("Комната № " + guests.get(position).getRoom());
        holder.name.setText("ФИО: " + guests.get(position).getName());
        ImageLoader.getInstance().displayImage(guests.get(position).getImage(), holder.image, options, animateFirstListener);
        holder.balance.setText("Баланс: " + guests.get(position).getBalance());
        holder.tarif.setText("Тариф: " + guests.get(position).getTarif());
        if (Float.parseFloat(guests.get(position).getBalance())>=0.0) {
            holder.balance.setTextColor(ctx.getResources().getColor(R.color.balance_positive));
        }else{
            holder.balance.setTextColor(ctx.getResources().getColor(R.color.balance_negative));
        }
        if (!guests.get(position).getCompany().equals("")) {
            holder.company.setText("Компания: " + guests.get(position).getCompany());
        }else{
            holder.company.setText("Компания: не указано");
        }
        if (!guests.get(position).getTotalNigth().equals("")) {
            holder.night.setText("Ночей: " + guests.get(position).getTotalNigth());
        }else{
            holder.night.setText("Ночей: не указано");
        }
        if (guests.get(position).isWifi()) {
            holder.wifi.setVisibility(View.VISIBLE);
        } else {
            holder.wifi.setVisibility(View.INVISIBLE);
        }
        if (guests.get(position).isInroom()) {
            holder.inroom.setImageResource(R.drawable.human_on);
        } else {
            holder.inroom.setImageResource(R.drawable.human_off);
        }
        if (guests.get(position).isCleaning()) {
            holder.cleaning.setVisibility(View.VISIBLE);
        } else {
            holder.cleaning.setVisibility(View.INVISIBLE);
        }
        if (guests.get(position).isTv()) {
            holder.tv.setVisibility(View.VISIBLE);
        } else {
            holder.tv.setVisibility(View.INVISIBLE);
        }
        if (guests.get(position).getCheckins().equals("0")) {
            holder.checkin.setVisibility(View.INVISIBLE);
        }
        if (guests.get(position).getCheckins().equals("")) {
            holder.checkin.setText("R?");
        }
        if (!guests.get(position).getCheckins().equals("") && !guests.get(position).getCheckins().equals("")) {
            holder.checkin.setText("R" + guests.get(position).getCheckins());
        }

        holder.cleaning.setOnClickListener(this);

        return view;
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.cleaningImg:
                Toast.makeText(ctx, "уборка", Toast.LENGTH_LONG).show();
                break;
        }
    }

    private static class ViewHolder {
        TextView number;
        TextView name;
        CircleImageView image;
        TextView balance;
        TextView company;
        TextView night;
        ImageView wifi;
        ImageView inroom;
        ImageView cleaning;
        ImageView tv;
        TextView checkin;
        TextView tarif;
    }
}

调用适配器的地方：

private ArrayList<GuestBean> guests;
..............
public void setData(){
        new MyAsincTask(getActivity()){
            @Override
            protected void onPreExecute() {
                count=0;
            }
            @Override
            protected void onPostExecute(Document document) {
                super.onPostExecute(document);
                guests = new ArrayList<>();
               Elements elementsUserId = document.select("guest_id");
            Elements elementsNumbers = document.select("room");
            Elements elementsNames = document.select("name");
            Elements elementsImageLinks = document.select("photo");
            Elements elementsBalance = document.select("balance");
            Elements elementsCompany = document.select("company");
            Elements elementsCountry = document.select("country");
            Elements elementsWiFi = document.select("wifi");
            Elements elementsInroom = document.select("inroom");
            Elements elementsCleaning = document.select("cleaning");
            Elements elementsTv = document.select("tv");
            Elements elementsTotalNigth = document.select("total_nights");
            Elements elementsCheckins = document.select("checkins");
            Elements elementsCheckin = document.select("checkin");
            Elements elementsCheckout = document.select("checkout");
            Elements elementsTarif = document.select("tariff");
            Elements elementsNigth = document.select("nights");


            for (int i = 0; i < elementsNumbers.size(); i++) {
                GuestBean guest = new GuestBean();
                guest.setUserId(elementsUserId.get(i).ownText());
                guest.setRoom(elementsNumbers.get(i).ownText());
                guest.setName(elementsNames.get(i).ownText());
                guest.setImage(elementsImageLinks.get(i).ownText());
                guest.setBalance(elementsBalance.get(i).ownText());
                guest.setCompany(elementsCompany.get(i).ownText());
                guest.setCountry(elementsCountry.get(i).ownText());
                guest.setWifi(Boolean.parseBoolean(elementsWiFi.get(i).ownText()));
                guest.setInroom(Boolean.parseBoolean(elementsInroom.get(i).ownText()));
                guest.setCleaning(Boolean.parseBoolean(elementsCleaning.get(i).ownText()));
                guest.setTv(Boolean.parseBoolean(elementsTv.get(i).ownText()));
                guest.setTotalNigth(elementsTotalNigth.get(i).ownText());
                guest.setCheckins(elementsCheckins.get(i).ownText());
                guest.setCheckin(elementsCheckin.get(i).ownText());
                guest.setCheckout(elementsCheckout.get(i).ownText());
                guest.setTarif(elementsTarif.get(i).ownText());
                guest.setNigth(elementsNigth.get(i).ownText());
                guests.add(guest);
                count++;
            }
                GuestsListAdapter adapter = new GuestsListAdapter(getActivity(), guests);
                list.setAdapter(adapter);
                progressDialog.cancel();
                swipeLayout.setRefreshing(false);
                header = "Гости " + hotel + "" + "(" + count + ")";
                getActivity().setTitle(header);
            }
        }.execute(link);
    }