Scroll JScrollPane by dragging mouse (Java swing) -

i making map editor game working on. there jpanel in jscrollpane displays map edited. make when user holding down spacebar , dragging mouse in jpanel, jscrollpanel scroll along dragging. here have far:

panelmappanel.addmousemotionlistener(new mousemotionlistener(){          @override         public void mousedragged(mouseevent e) {             //gets difference in distance x , y last time listener called             int deltax = mousex - e.getx();             int deltay = mousey - e.gety();             mousex = e.getx();             mousey = e.gety();             if(spacepressed){                 //scroll scrollpane according distance travelled                 scrollpane.getverticalscrollbar().setvalue(scrollpane.getverticalscrollbar().getvalue() + deltay);                 scrollpane.gethorizontalscrollbar().setvalue(scrollpane.gethorizontalscrollbar().getvalue() + deltax);             }         }  }); 

currently works scrolling not smooth @ all. moving mouse lot @ time fine doing small drags makes scrollpane go berserk.

any ideas how improve this?

for enjoy visual help, here editor:

addition notes (edit):

• i have tried scrollpane.getviewport().setviewposition(new point(scrollpane.getviewport().getviewposition().x + deltax, scrollpane.getviewport().getviewposition().y + deltay));
• the dragging more fidgety when moving mouse slowly, while big movements more smooth
• i tried using scrollrecttovisible without luck

okay, ended been simpler though be...

first, don't mess jviewport, instead, use jcomponent#scrollrecttovisible directly on component acting contents of jscrollpane, onto mouselistener should attached.

the following example calculates difference between point @ user clicked , amount have dragged. applies delta jviewport's viewrect , uses jcomponent#scrollrecttovisible update viewable area, simple :)

public class test {      public static void main(string[] args) {         new test();     }      public test() {         eventqueue.invokelater(new runnable() {             @override             public void run() {                 try {                     uimanager.setlookandfeel(uimanager.getsystemlookandfeelclassname());                 } catch (classnotfoundexception | instantiationexception | illegalaccessexception | unsupportedlookandfeelexception ex) {                     ex.printstacktrace();                 }                  jframe frame = new jframe("testing");                 frame.setdefaultcloseoperation(jframe.exit_on_close);                 frame.add(new testpane());                 frame.pack();                 frame.setlocationrelativeto(null);                 frame.setvisible(true);             }         });     }      public class testpane extends jpanel {          private jlabel map;          public testpane() {             setlayout(new borderlayout());             try {                 map = new jlabel(new imageicon(imageio.read(new file("c:/treasuremap.jpg"))));                 map.setautoscrolls(true);                 add(new jscrollpane(map));                  mouseadapter ma = new mouseadapter() {                      private point origin;                      @override                     public void mousepressed(mouseevent e) {                         origin = new point(e.getpoint());                     }                      @override                     public void mousereleased(mouseevent e) {                     }                      @override                     public void mousedragged(mouseevent e) {                         if (origin != null) {                             jviewport viewport = (jviewport) swingutilities.getancestorofclass(jviewport.class, map);                             if (viewport != null) {                                 int deltax = origin.x - e.getx();                                 int deltay = origin.y - e.gety();                                  rectangle view = viewport.getviewrect();                                 view.x += deltax;                                 view.y += deltay;                                  map.scrollrecttovisible(view);                             }                         }                     }                  };                  map.addmouselistener(ma);                 map.addmousemotionlistener(ma);             } catch (ioexception ex) {                 ex.printstacktrace();             }         }          @override         public dimension getpreferredsize() {             return new dimension(200, 200);         }      }  }