android - How to call function in Activity from HomeScreen Widget -

what proper method of calling function in application's activity widget located on home screen? example, have background thread initialized in activity class, , able press widget home screen call specific functions start/stop thread without having enter application.

below stripped , barebone version of activity working with:

public class mainactivity extends appcompatactivity {     private thread thread;     private runnable runner;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         startthread();     }      private void startthread() {         //start/restart thread     }      public void stopthread() {         //interupt thread     }    } 

below barebone code home screen widget:

static void updateappwidget(context context, appwidgetmanager appwidgetmanager, int appwidgetid) {      intent intent = new intent(context, mainactivity.class);      intent.putextra("goal","stop");     pendingintent pendingintent = pendingintent.getactivity(context, 0, intent, 0);      remoteviews views = new remoteviews(context.getpackagename(), r.layout.speed_widget);     views.setonclickpendingintent(r.id.widgetbutton, pendingintent);      appwidgetmanager.updateappwidget(appwidgetid, views); } 

here current best solution is: research i've done far, seems need continue use putextra() , getextra() intent sent widget, , add in string whether call startthread() or stopthread() based on status of thread. current goal use this:

    string intentgoal = getintent().getextras().getstring("goal");     if(intentgoal.compareto("stop")==0){         stopthread();     }else if(intentgoal.compareto("start")==0){         startthread();     } 

and ran in overloaded version of onnewintent(). however, intent sent widget results in call oncreate() well, don't want have happen since restart thread , various other initialization code have re-ran well. tried setting launchmode singletask, still call oncreate() rather onnewintent(). recap, able press home screen widget, , have start or stop thread, or more call specific function in existing `mainactivity'.

i'm not expert in widget-building-process, assume need change:

pendingintent pendingintent = pendingintent.getactivity(context, 0, intent, 0); 

to:

pendingintent pendingintent = pendingintent.getbroadcast(context, 0, intent, 0); 

since need provide interaction application, don't need attach widget specific activity. instead of need use messaging mechanism. in android it's broadcastreciever. example, use interact "start" service. can read here simple example.

also, according this answer came solution, need register reciever in manifest:

then in onrecieve method can parse intent , whatever want. in case, recomend transport working background activity service, since activity can closed (okey, service too, can restored , run without screen). , in mywidgetreciever.onreceive need start service passing "stop" intent.

i'm not sure, but, can catch broadcast in service directly, not in external reciever, situation when service killed, not handle broadcast.