android - Stop AsyncTask doInBackground method -

i have created asynctask in class , calling task fragment. problem want stop doinbackground method if fragment destroyed. created method in class asynctask written , used cancel(true) on asynctask object in method. when call method fragments ondestroy() background process still running. plz tell me right way stop asynctask's doinbackground.

this class asynctask written

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;      // loaded later - or can set 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 reference adapter         this.caradapter = caradapter;         if (thumburl != null && !thumburl.equals("")) {             //new imageloadtask().execute(thumburl);              task.execute(thumburl);         }  }      // async task avoid choking ui thread     private class imageloadtask extends asynctask<string, string, bitmap> {          @override         protected void onpreexecute() {             log.i("imageloadtask", "loading image...");         }          // param[0] img url         protected bitmap doinbackground(string... param) {             log.i("imageloadtask", "attempting 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 loaded notify adapter                     caradapter.notifydatasetchanged();                 }             } else {                 log.e("imageloadtask", "failed load " + carname + " image");             }         }     }       /* below here implementing parcelable */      // 99.9% of time can ignore     public int describecontents() {         return 0;     }      // write object's data 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);      }      // used regenerate object. parcelables must have creator implements these 2 methods     public static final parcelable.creator<cardetail> creator = new parcelable.creator<cardetail>() {         public cardetail createfromparcel(parcel in) {             return new cardetail(in);         }          public cardetail[] newarray(int size) {             return new cardetail[size];         }     };      // example constructor takes parcel , gives object populated 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"); } 

this fragment

 public class servicecarlistfragment extends fragment {  private string url; private arraylist<cardetail> cardetaillist = new arraylist<cardetail>(); private carlistadapter adapter; private listview mlist ; private progressdialog progressdialog; oncarlistitemselectedlistener mcallback; private boolean connectionstatus;  // container activity must implement interface public interface oncarlistitemselectedlistener {     public void oncarselected(cardetail car); }  @override public void onattach(activity activity) {     // todo auto-generated method stub     super.onattach(activity);     // makes sure container activity has implemented     // callback interface. if not, throws 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<?> 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<string, string, arraylist<cardetail>>{        @override     protected void onpreexecute() {         // todo auto-generated method stub         super.onpreexecute();         progressdialog = progressdialog.show(getactivity(), null, "loading...",true);      }      @override     protected arraylist<cardetail> doinbackground(string... params) {         // todo auto-generated method stub         arraylist<cardetail> cardetaillist = jsonparser.parsejson(params[0]);         return cardetaillist;     }      @override     protected void onpostexecute(arraylist<cardetail> 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();         (cardetail car : cardetaillist) {             // start loading images 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(); }  } 

public final boolean cancel (boolean mayinterruptifrunning)

attempts cancel execution of task. this attempt fail if task has completed, been cancelled, or not cancelled other reason. if successful, , task has not started when cancel called, task should never run. if task has started, mayinterruptifrunning parameter determines whether thread executing task should interrupted in attempt stop task.

use iscancelled()

public final boolean iscancelled ()

returns true if task cancelled before completed normally. if calling cancel(boolean) on task, value returned method should checked periodically doinbackground(object[]) end task possible.

android - cancel asynctask forcefully

check accepted answer , answer commonsware in above link