title: Stop AsyncTask doInBackground method
body: <p>I have created an AsyncTask in a class and i am calling that task from a fragment. The problem is i want to stop the doInBackground method if the fragment is destroyed. To do that i created a method in the class where AsyncTask is written and i used cancel(true) on Asynctask object in that method. When i call this method from fragments onDestroy() the background process is still running. Plz tell me the right way to stop asynctask's doInBackground.</p>
  
  <p>This is the class where asynctask is written</p>
  
  <pre><code>public class CarDetail implements Parcelable{
  
  private String carId;
  private String carName;
  private String imageUrl;
  private String thumbUrl;
  private String dailyPrice;
  private String weeklyPrice;
  private String weekendPrice;
  private String deposit;
  private String minimumAge;
  private String color;
  private String make;
  private String location;
  private String bodyType;
  private String fuelType;
  private String transmission;
  private String carType;
  private String model;
  private String description;
  private Bitmap image;
  private Bitmap thumbImage;
  private CarListAdapter carAdapter;
  private ImageLoadTask task = new ImageLoadTask();
  
  public CarDetail() {
      super();
      // TODO Auto-generated constructor stub
  }
  
  public CarDetail(String carId, String carName, String imageUrl,
          String thumbUrl, String dailyPrice, String weeklyPrice,
          String weekendPrice, String deposit, String minimumAge,
          String color, String make, String location, String bodyType,
          String fuelType, String transmission, String carType, String model,
          String description) {
      super();
      this.carId = carId;
      this.carName = carName;
      this.imageUrl = imageUrl;
      this.thumbUrl = thumbUrl;
      this.dailyPrice = dailyPrice;
      this.weeklyPrice = weeklyPrice;
      this.weekendPrice = weekendPrice;
      this.deposit = deposit;
      this.minimumAge = minimumAge;
      this.color = color;
      this.make = make;
      this.location = location;
      this.bodyType = bodyType;
      this.fuelType = fuelType;
      this.transmission = transmission;
      this.carType = carType;
      this.model = model;
      this.description = description;
  
      // TO BE LOADED LATER - OR CAN SET TO A DEFAULT IMAGE
      this.image = null;
      this.thumbImage = null;
  }
  
  public String getCarId() {
      return carId;
  }
  
  public void setCarId(String carId) {
      this.carId = carId;
  }
  
  public String getCarName() {
      return carName;
  }
  
  public void setCarName(String carName) {
      this.carName = carName;
  }
  
  public String getImageUrl() {
      return imageUrl;
  }
  
  public void setImageUrl(String imageUrl) {
      this.imageUrl = imageUrl;
  }
  
  public String getThumbUrl() {
      return thumbUrl;
  }
  
  public void setThumbUrl(String thumbUrl) {
      this.thumbUrl = thumbUrl;
  }
  
  public String getDailyPrice() {
      return dailyPrice;
  }
  
  public void setDailyPrice(String dailyPrice) {
      this.dailyPrice = dailyPrice;
  }
  
  public String getWeeklyPrice() {
      return weeklyPrice;
  }
  
  public void setWeeklyPrice(String weeklyPrice) {
      this.weeklyPrice = weeklyPrice;
  }
  
  public String getWeekendPrice() {
      return weekendPrice;
  }
  
  public void setWeekendPrice(String weekendPrice) {
      this.weekendPrice = weekendPrice;
  }
  
  public String getDeposit() {
      return deposit;
  }
  
  public void setDeposit(String deposit) {
      this.deposit = deposit;
  }
  
  public String getMinimumAge() {
      return minimumAge;
  }
  
  public void setMinimumAge(String minimumAge) {
      this.minimumAge = minimumAge;
  }
  
  public String getColor() {
      return color;
  }
  
  public void setColor(String color) {
      this.color = color;
  }
  
  public String getMake() {
      return make;
  }
  
  public void setMake(String make) {
      this.make = make;
  }
  
  public String getLocation() {
      return location;
  }
  
  public void setLocation(String location) {
      this.location = location;
  }
  
  public String getBodyType() {
      return bodyType;
  }
  
  public void setBodyType(String bodyType) {
      this.bodyType = bodyType;
  }
  
  public String getFuelType() {
      return fuelType;
  }
  
  public void setFuelType(String fuelType) {
      this.fuelType = fuelType;
  }
  
  public String getTransmission() {
      return transmission;
  }
  
  public void setTransmission(String transmission) {
      this.transmission = transmission;
  }
  
  public String getCarType() {
      return carType;
  }
  
  public void setCarType(String carType) {
      this.carType = carType;
  }
  
  public String getModel() {
      return model;
  }
  
  public void setModel(String model) {
      this.model = model;
  }
  
  public String getDescription() {
      return description;
  }
  
  public void setDescription(String description) {
      this.description = description;
  }
  
  public Bitmap getImage() {
      return image;
  }
  
  public void setImage(Bitmap image) {
      this.image = image;
  }
  
  public Bitmap getThumbImage() {
      return thumbImage;
  }
  
  public void setThumbImage(Bitmap thumbImage) {
      this.thumbImage = thumbImage;
  }
  
   public void loadImage(CarListAdapter carAdapter) {
          // HOLD A REFERENCE TO THE ADAPTER
          this.carAdapter = carAdapter;
          if (thumbUrl != null &amp;&amp; !thumbUrl.equals("")) {
              //new ImageLoadTask().execute(thumbUrl);
  
              task.execute(thumbUrl);
          }
   }
  
      // ASYNC TASK TO AVOID CHOKING UP UI THREAD
      private class ImageLoadTask extends AsyncTask&lt;String, String, Bitmap&gt; {
  
          @Override
          protected void onPreExecute() {
              Log.i("ImageLoadTask", "Loading image...");
          }
  
          // PARAM[0] IS IMG URL
          protected Bitmap doInBackground(String... param) {
              Log.i("ImageLoadTask", "Attempting to load image URL: " + param[0]);
              try {
                  Bitmap b = JsonParser.downloadBitmap(param[0]);
                  return b;
              } catch (Exception e) {
                  e.printStackTrace();
                  return null;
              }
          }
  
          protected void onProgressUpdate(String... progress) {
              // NO OP
          }
  
          protected void onPostExecute(Bitmap ret) {
              if (ret != null) {
                  Log.i("ImageLoadTask", "Successfully loaded " + carName + " image");
                  image = ret;
                  if (carAdapter != null) {
                      // WHEN IMAGE IS LOADED NOTIFY THE ADAPTER
                      carAdapter.notifyDataSetChanged();
                  }
              } else {
                  Log.e("ImageLoadTask", "Failed to load " + carName + " image");
              }
          }
      }
  
  
      /* everything below here is for implementing Parcelable */
  
      // 99.9% of the time you can just ignore this
      public int describeContents() {
          return 0;
      }
  
      // write your object's data to the passed-in Parcel
      public void writeToParcel(Parcel out, int flags) {
          out.writeString(carId);
          out.writeString(carName);
          out.writeString(imageUrl);
          out.writeString(thumbUrl);
          out.writeString(dailyPrice);
          out.writeString(weeklyPrice);
          out.writeString(weekendPrice);
          out.writeString(deposit);
          out.writeString(minimumAge);
          out.writeString(color);
          out.writeString(make);
          out.writeString(location);
          out.writeString(bodyType);
          out.writeString(fuelType);
          out.writeString(transmission);
          out.writeString(carType);
          out.writeString(model);
          out.writeString(description);
  
      }
  
      // this is used to regenerate your object. All Parcelables must have a CREATOR that implements these two methods
      public static final Parcelable.Creator&lt;CarDetail&gt; CREATOR = new Parcelable.Creator&lt;CarDetail&gt;() {
          public CarDetail createFromParcel(Parcel in) {
              return new CarDetail(in);
          }
  
          public CarDetail[] newArray(int size) {
              return new CarDetail[size];
          }
      };
  
      // example constructor that takes a Parcel and gives you an object populated with it's values
      private CarDetail(Parcel in) {
          carId = in.readString();
          carName = in.readString();
          imageUrl = in.readString();
          thumbUrl = in.readString();
          dailyPrice = in.readString();
          weeklyPrice = in.readString();
          weekendPrice = in.readString();
          deposit = in.readString();
          minimumAge = in.readString();
          color = in.readString();
          make = in.readString();
          location  = in.readString();
          bodyType = in.readString();
          fuelType = in.readString();
          transmission = in.readString();
          carType = in.readString();
          model = in.readString();
          description = in.readString();
  
      }
  
  
  
   public void stopImageLoadTask(){
      task.cancel(true);
      Log.d("stop", "stop");
  }
  </code></pre>
  
  <p>This is the fragment</p>
  
  <pre><code> public class ServiceCarListFragment extends Fragment {
  
  private String url;
  private ArrayList&lt;CarDetail&gt; carDetailList = new ArrayList&lt;CarDetail&gt;();
  private CarListAdapter adapter;
  private ListView mList ;
  private ProgressDialog progressDialog;
  OnCarListItemSelectedListener mCallback;
  private boolean connectionStatus;
  
  // Container Activity must implement this interface
  public interface OnCarListItemSelectedListener {
      public void onCarSelected(CarDetail car);
  }
  
  @Override
  public void onAttach(Activity activity) {
      // TODO Auto-generated method stub
      super.onAttach(activity);
      // This makes sure that the container activity has implemented
      // the callback interface. If not, it throws an exception
      try {
          mCallback = (OnCarListItemSelectedListener) activity;
      } catch (ClassCastException e) {
          throw new ClassCastException(activity.toString()
                  + " must implement OnCarListItemSelectedListener");
      }
  }
  
  
  
  
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
      // TODO Auto-generated method stub
      super.onCreate(savedInstanceState);
      Log.d("Services", "On Create");
      url = getActivity().getIntent().getStringExtra("url");
      adapter = new CarListAdapter(getActivity() , carDetailList);
  
      ConnectionHandler conn = new ConnectionHandler();
      connectionStatus = conn.connectionStatus(getActivity());
  
      if(connectionStatus){
  
          new DownloadCarDetail().execute(url);
      }
  
      else{
          DialogFragment newFragment = new DialogHandler(getActivity());
          newFragment.show(getFragmentManager(), "internet");
      }
  
  
  }
  
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
          Bundle savedInstanceState) {
      // TODO Auto-generated method stub
      Log.d("Services", "On CreateView");
      View v = inflater.inflate(R.layout.fragment_service_car_list, container,false);
      mList = (ListView)v.findViewById(R.id.list);
      mList.setAdapter(adapter);  
      mList.setOnItemClickListener(new OnItemClickListener() {
  
          @Override
          public void onItemClick(AdapterView&lt;?&gt; parent, View selectedView, int position,
                  long id) {
              // TODO Auto-generated method stub
              CarDetail car = (CarDetail)adapter.getItem(position);
              mCallback.onCarSelected(car);
          }
      });
      return v;
  }
  
  class DownloadCarDetail extends AsyncTask&lt;String, String, ArrayList&lt;CarDetail&gt;&gt;{
  
  
  
      @Override
      protected void onPreExecute() {
          // TODO Auto-generated method stub
          super.onPreExecute();
          progressDialog = ProgressDialog.show(getActivity(), null, "Loading...",true);
  
      }
  
      @Override
      protected ArrayList&lt;CarDetail&gt; doInBackground(String... params) {
          // TODO Auto-generated method stub
          ArrayList&lt;CarDetail&gt; carDetailList = JsonParser.parseJson(params[0]);
          return carDetailList;
      }
  
      @Override
      protected void onPostExecute(ArrayList&lt;CarDetail&gt; carDetailList) {
          // TODO Auto-generated method stub
          //adapter = new CarListAdapter(getActivity(),ServiceCarListFragment.this.carDetailList);
          //mList.setAdapter(adapter);
          progressDialog.dismiss();
          ServiceCarListFragment.this.carDetailList.addAll(carDetailList);
          adapter.notifyDataSetChanged();
          for (CarDetail car : carDetailList) {
              // START LOADING IMAGES FOR EACH CAR
              car.loadImage(adapter);
  
      }
          carDetailList.clear();
          Log.d("ewgf", String.valueOf(carDetailList.size()));
   }
  
  }
  
  
  
  @Override
  public void onDestroy() {
      // TODO Auto-generated method stub
      super.onDestroy();
      new CarDetail().stopImageLoadTask();
  }
  
  }
  </code></pre>