How to load a ListView using AsyncTask in android -

i have method called fetchdata() fetch data database , load listview. when activity starts there small lag because of this. need load data in background. wondering if tell me how using asynctask.

this fetchdata() method.

public void fetchdata() {     database = helper.getreadabledatabase();     cursor c;     date cdate = new date();     simpledateformat sdf=new simpledateformat("yyyy-mm-dd");     final string fdate = sdf.format(cdate);      int thismonth=integer.parseint(fdate.split("-")[1]);     month mn=new month();     string month=mn.getmonth(thismonth);      calendar cal=calendar.getinstance();      int today=integer.parseint(fdate.split("-")[2]);      int curtab=position;     string whereclause="";     string sort="";     if(curtab==0){         whereclause=null;         sort=database.name;     }     else if(curtab==1){         whereclause=database.month+" = '"+month+"' , "+database.day+" ="+today;         sort=database.name;     }     else if(curtab==2){         cal.add(calendar.day_of_month, 1);         int monthn=cal.get(calendar.month)+1;         month mnn=new month();         string monthtomorrow=mnn.getmonth(monthn);          int tomorrow=cal.get(calendar.day_of_month);         whereclause=database.month+" = '"+monthtomorrow+"' , "+database.day+" ="+tomorrow;         sort=database.day;     }     else if(curtab==3){         whereclause=database.month+" = '"+month+"'";         sort=database.day;     }      if(drawermain.pos==1){         if(curtab==0){             whereclause=database.type+"='birthday'";         }         else{             whereclause=whereclause+" , "+database.type+"='birthday'";         }     }     else if(drawermain.pos==2){         if(curtab==0){             whereclause=database.type+"='anniversary'";         }         else{             whereclause=whereclause+" , "+database.type+"='anniversary'";         }     }      c = database.query(database.table_event, null, whereclause, null, null, null, sort);      string[] fromdb={database.name,database.month,database.day};     int[] toview={r.id.tvname_lv,r.id.tv_month_lv,r.id.tv_day_lv};      customcursoradapter adapter=new customcursoradapter(getactivity(), c, 0, r.layout.events_list_item,fromdb,toview);     lv.setadapter(adapter);     database.close(); } 

you should consider using asynctaskloader instead. asyncloaders handle orientation changes better asynctasks.

you can find tutorial here: http://www.androiddesignpatterns.com/2012/08/implementing-loaders.html

code (copied directly tutorial)

  public class sampleloader extends asynctaskloader<list<sampleitem>> {    // hold reference loader’s data here.   private list<sampleitem> mdata;    public sampleloader(context ctx) {     // loaders may used across multiple activitys (assuming aren't     // bound loadermanager), never hold reference context     // directly. doing cause leak entire activity's context.     // superclass constructor store reference application     // context instead, , can retrieved call getcontext().     super(ctx);   }    /****************************************************/   /** (1) task performs asynchronous load **/   /****************************************************/    @override   public list<sampleitem> loadinbackground() {     // method called on background thread , should generate     // new set of data delivered client.     list<sampleitem> data = new arraylist<sampleitem>();      // todo: perform query here , add results 'data'.      return data;   }    /********************************************************/   /** (2) deliver results registered listener **/   /********************************************************/    @override   public void deliverresult(list<sampleitem> data) {     if (isreset()) {       // loader has been reset; ignore result , invalidate data.       releaseresources(data);       return;     }      // hold reference old data doesn't garbage collected.     // must protect until new data has been delivered.     list<sampleitem> olddata = mdata;     mdata = data;      if (isstarted()) {       // if loader in started state, deliver results       // client. superclass method us.       super.deliverresult(data);     }      // invalidate old data don't need more.     if (olddata != null && olddata != data) {       releaseresources(olddata);     }   }    /*********************************************************/   /** (3) implement loader’s state-dependent behavior **/   /*********************************************************/    @override   protected void onstartloading() {     if (mdata != null) {       // deliver loaded data immediately.       deliverresult(mdata);     }      // begin monitoring underlying data source.     if (mobserver == null) {       mobserver = new sampleobserver();       // todo: register observer     }      if (takecontentchanged() || mdata == null) {       // when observer detects change, should call oncontentchanged()       // on loader, cause next call takecontentchanged()       // return true. if ever case (or if current data       // null), force new load.       forceload();     }   }    @override   protected void onstoploading() {     // loader in stopped state, should attempt cancel      // current load (if there one).     cancelload();      // note leave observer is. loaders in stopped state     // should still monitor data source changes loader     // know force new load if ever started again.   }    @override   protected void onreset() {     // ensure loader has been stopped.     onstoploading();      // @ point can release resources associated 'mdata'.     if (mdata != null) {       releaseresources(mdata);       mdata = null;     }      // loader being reset, should stop monitoring changes.     if (mobserver != null) {       // todo: unregister observer       mobserver = null;     }   }    @override   public void oncanceled(list<sampleitem> data) {     // attempt cancel current asynchronous load.     super.oncanceled(data);      // load has been canceled, should release resources     // associated 'data'.     releaseresources(data);   }    private void releaseresources(list<sampleitem> data) {     // simple list, there nothing do. cursor,      // close in method. resources associated loader     // should released here.   }    /*********************************************************************/   /** (4) observer receives notifications when data changes **/   /*********************************************************************/    // note: implementing observer outside scope of post (this example   // uses made-up "sampleobserver" illustrate when/where observer should    // initialized).     // observer long able detect content changes   // , report them loader call oncontentchanged(). example,   // if writing loader loads list of installed applications   // on device, observer broadcastreceiver listens   // action_package_added intent, , calls oncontentchanged() on particular    // loader whenever receiver detects new application has been installed.   // please don’t hesitate leave comment if still find confusing! :)   private sampleobserver mobserver; } 

put fetchdata() method in loadinbackground(). close cursor in releaseresources() method. in oncreate() call

    getloadermanager().initloader(0, null, this);