multithreading - How can a background thread modify the UI in between Activity loads in Android? -

i have download process runs in background, , updates ui progress (a listview adapter). works fine until leave activity , come back. after loading activity again there "new" listview object not same 1 bound bg download process. how can structure code background process can talk listview in activity?

the specific line is:

adapter.notifydatasetchanged(); 

here shell of download class:

public class download {    }    protected void start()     {        transfermanager tx           = new transfermanager(credentials);       this.download                = tx.download(s3_bucket, s3_dir + arr_videos.get(position), new_video_file);         download.addprogresslistener(new progresslistener()        {         public void progresschanged(final progressevent pe)          {           handler.post( new runnable()            {             @override             public void run()              {               if ( pe.geteventcode() == progressevent.completed_event_code )               {                 download.this.oncomplete();               }               else               {                 download.this.onprogressupdate();               }             }           });         }       });    }     protected void onprogressupdate()    {       this.download_status         = "downloading";       double progress = this.download.getprogress().getpercenttransfered();       integer percent  = progress.intvalue();       //log.v("runnable", percent + "");        downloaded_data.edit().putint(position+"", percent).commit();         adapter.notifydatasetchanged();    } } 

the short answer "no". there's no simple way find/keep reference listview in destroyed/recreated activity.

one way can around use broadcastreceiver. can broadcast progress intents, , have activity register/deregister intents in oncreate() , onpause().

another (arguably easier) hack can persist state (along lines of you're doing downloaded_data.edit()), , have thread in activity regularly polls state , updates listview accordingly.