android - How to update SQL database from within an onClick event of button inside a ListView -

how handle onclick events of button within listview item. fetching data of content provider in app. implemented custom simplecursoradapter not update database within onclick event. find below customsimplecursoradapter code.

i warming android. might missing simple. appreciated

public class customsimplecursoradapter extends simplecursoradapter {         private context mcontext;         private context appcontext;         private int layout;         private cursor cr;         private final layoutinflater inflater;          public customsimplecursoradapter(context context, int layout, cursor c, string[] from, int[] to,int flag) {             super(context, layout, c, from, to,flag);             this.layout = layout;             this.mcontext = context;             this.inflater = layoutinflater.from(context);             this.cr = c;         }          @override         public view newview(context context, cursor cursor, viewgroup parent) {             return inflater.inflate(layout, null);         }          @override         public void bindview(view view, context context, cursor cursor) {             super.bindview(view, context, cursor);             textview name =(textview)view.findviewbyid(r.id.productname_value);             final textview quantity = (textview) view.findviewbyid(r.id.availableinventory_value);             textview price = (textview) view.findviewbyid(r.id.price_value);             textview sales = (textview) view.findviewbyid(r.id.unitssold_value);             button sellbutton =(button)view.findviewbyid(r.id.sellbutton);               int name_index = cursor.getcolumnindexorthrow(inventorytable.column_name);             int quantity_index = cursor.getcolumnindexorthrow(inventorytable.column_quantity);             int price_index =cursor.getcolumnindexorthrow(inventorytable.column_price);             int sales_index = cursor.getcolumnindexorthrow(inventorytable.column_sales);               name.settext(cursor.getstring(name_index));             quantity.settext(cursor.getstring(quantity_index));             price.settext(cursor.getstring(price_index));             sales.settext(cursor.getstring(sales_index));             log.i("check before","check ok");              sellbutton.setonclicklistener(new view.onclicklistener() {                 @override                 public void onclick(view v) {                     uri produri = uri.parse(myinventorycontentprovider.content_uri + "/" + v.getid());                     contentvalues values = new contentvalues();                     string new_quantity = string.valueof(integer.parseint(quantity.gettext().tostring()) - 1);                     values.put(inventorytable.column_quantity,new_quantity);    inventoryupdatetask().execute(myinventorycontentprovider.content_uri.tostring(), inventorytable.column_quantity, new_quantity, inventorytable.column_id, string.valueof(v.getid()));                  }             });          }         private class inventoryupdatetask extends asynctask<string, void, void> {              private myinventorycontentprovider dbhelper = new myinventorycontentprovider();             @override             protected void doinbackground(string... params) {                 contentvalues values = new contentvalues();                     values.put(params[1], integer.parseint(params[2]));                 dbhelper.oncreate();                 dbhelper.update(uri.parse(params[0]), values, params[3], new string[]{params[4]});                 return null;             }              @override             protected void onpostexecute(void result) {              }         }      }