listView.setOnScrollListener(new OnScrollListener() {
                public void onScrollStateChanged(AbsListView view, int scrollState) {
                }
                public void onScroll(AbsListView view, int firstVisibleItem,
                        int visibleItemCount, int totalItemCount) {
                    if(loading){
                        //if trying to loading
                        if(totalItemCount > previousTotal){
                        loading = false;
                        previousTotal = totalItemCount;
                        }
                        }
                    if(!loading && ((totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold))){
                        limit=limit+10;
                                    AlertSearchAsync task1=new AlertSearchAsync();
                            String url="http://www.jobdiagnosis.com/fjobsrchservise.php?keyword="+
                                    str_descAlert+
                                    "&location="+str_locAlert+
                                    "&limit="+limit;
                            url=url.replace(" ", "%20");
                            //Toast.makeText(getApplicationContext(),"Limit"+limit, Toast.LENGTH_LONG).show();
                            task1.execute(url);
                   }
            });
first time asyn class call perfect and after that when scroll one and two item then call asyn class and updated listview and list view selected at top
 
     
     
    