java - How can I update JPanel continuously? -

i've got slight problem, i'm writing gps tracking app track several objects @ once. data comes in on serial interface, coming in fine can tell. issue need continually update jpanel map created , displayed.

public jpanel mapdisplay(){     jpanel mappanel = new jpanel();     mappanel.setsize(560, 540);     coordinate start = new coordinate (-34.9286, 138.6);     trackmap.addmapmarker(new mapmarkerdot(1lat, 1lon));     trackmap.setdisplayposition(start,8);     system.out.println(1lat);      mappanel.add(trackmap);     mappanel.setvisible(true);     return mappanel; } 

this have , it's happy display point once won't update. if print out 1lat variable in serial method continually prints, once here.

a lot of answers i've found refer setting markers arrays, won't work in case objects i'm tracking anywhere.

any appreciated :)

is possible use worker thread , not use arraylist? run risk of missing data if do.

not necessarily. in swingworker, implementation of doinbackground() method can publish() results become available. note in particular "results multiple invocations of publish() accumulated single invocation of process()." in process(), loop through list<coordinate>, update route , repaint() map.

import java.awt.color; import java.awt.dimension; import java.awt.eventqueue; import java.awt.event.mouseevent; import java.util.arraylist; import java.util.list; import javax.swing.jframe; import javax.swing.swingworker; import org.openstreetmap.gui.jmapviewer.coordinate; import org.openstreetmap.gui.jmapviewer.jmapviewer; import org.openstreetmap.gui.jmapviewer.mappolygonimpl;  /**  * @see http://stackoverflow.com/a/37193636/230513  */ public class mapworkertest {      private final list<coordinate> route = new arraylist<>();      private void display() {         jframe f = new jframe("mapworker");         f.setdefaultcloseoperation(jframe.exit_on_close);         jmapviewer map = new jmapviewer() {              @override             public dimension getpreferredsize() {                 return new dimension(640, 480);             }              @override             public string gettooltiptext(mouseevent e) {                 coordinate c = (coordinate) getposition(e.getx(), e.gety());                 return c.getlat() + " " + c.getlon();             }         };         map.settooltiptext("");         coordinate start = new coordinate(-34.9286, 138.6);         route.add(start);         mappolygonimpl poly = new mappolygonimpl(route);         poly.setcolor(color.blue);         map.addmappolygon(poly);         map.setdisplayposition(start, 10);         f.add(map);         f.pack();         f.setlocationrelativeto(null);         f.setvisible(true);         new mapworker(map, start).execute();     }      private class mapworker extends swingworker<void, coordinate> {          private final jmapviewer map;         private coordinate last;          public mapworker(jmapviewer map, coordinate start) {             this.map = map;             this.last = start;         }          @override         protected void doinbackground() throws exception {             while (!iscancelled()) {                 last = new coordinate(last.getlat() + 0.0025, last.getlon() + 0.01);                 publish(last);                 thread.sleep(1000);             }             return null;         }          @override         protected void process(list<coordinate> chunks) {             (coordinate c : chunks) {                 route.add(c);             }             map.repaint();         }     }      public static void main(string[] args) {         eventqueue.invokelater(new mapworkertest()::display);     } } 

multiple route management left exercise.