java - JavaFX: Having issues making a draggable node -

i'm attempting make node i've created draggable.

i'm able place nodes @ point in pane, when comes dragging them around, seem automatically offput.

i've tried making delta class contain x , y updated accordingly during pressing of mouse on node.

nfapane.setonmousepressed(event -> {             if (!event.getbutton().equals(mousebutton.primary)) return;             (final nfanode node : nfanodes)                 if (node.ishover())                     return;             final nfanode nfanode = new nfanode(nfanodes.size(), event.getx(), event.gety());             nfapane.getchildren().add(nfanode);             nfanodes.add(nfanode);             delta dragdelta = new delta();             nfanode.setonmousepressed(event1 -> {                 dragdelta.setdragdeltax(nfanode.getlayoutx());                 dragdelta.setdragdeltay(nfanode.getlayouty());             });              nfanode.setonmousedragged(event1 -> {                 nfanode.moveto(event1.getscenex() + dragdelta.getdragdeltax(), event1.getsceney() + dragdelta.getdragdeltay());             });         }); 

the node defined class nfanode:

package sample;  import javafx.scene.group; import javafx.scene.paint.color; import javafx.scene.shape.ellipse; import javafx.scene.text.font; import javafx.scene.text.text;  /**  * created david on 11/5/2016.  */ public class nfanode extends group {     //private list<nfanode> next;     public static final font nfafont = font.font("footlight mt light", 25);     private final ellipse bubble;     private final text text;     private double textwidth;      public nfanode(int value, double x, double y) {         this.text = new text(x, y + 5, "");         renumber(value);         this.text.setfont(nfafont);         textwidth = this.text.getboundsinlocal().getwidth();         bubble = new ellipse(x, y, this.text.getboundsinlocal().getwidth() + 5, 25);         this.text.setx(x - textwidth / 2);         bubble.setstroke(color.black);         bubble.setfill(color.white);         getchildren().addall(bubble, this.text);     }      public text gettext() {         return text;     }      public void renumber(final int value) {         final stringbuilder builder = new stringbuilder();         (char c : string.valueof(value).tochararray()) builder.append((char) (c + 8272));         text.settext("q" + builder.tostring());     }      public void moveto(final double x, final double y) {         bubble.setcenterx(x);         bubble.setcentery(y);         text.setx(x - textwidth / 2);         text.sety(y + 5);     } } 

i'm confused why affect position of node when dragged?

you forgot take mouse position account when it's pressed.

you've got following equation

mouseposition - mousepressedposition = targetposition - startposition 

so dragdelta should be

startposition - mousepressedposition = targetposition - mouseposition 

personally prefer using coordinate system of parent, using scene coordinates should work too, unless you've got transformations in place, not translations.

example

private static class delta {      private double dragdeltax;     private double dragdeltay;      public double getdragdeltax() {         return dragdeltax;     }      public double getdragdeltay() {         return dragdeltay;     }      public void setdragdelta(double x, double y) {         this.dragdeltax = x;         this.dragdeltay = y;     } }  @override public void start(stage primarystage) {     circle c = new circle(30);     c.setlayoutx(50);     c.setlayouty(50);      pane root = new pane(c);      delta dragdelta = new delta();      c.setonmousepressed(event1 -> {         point2d mouseinparent = c.localtoparent(event1.getx(), event1.gety());         dragdelta.setdragdelta(c.getlayoutx() - mouseinparent.getx(), c.getlayouty()-mouseinparent.gety());         event1.consume();     });      c.setonmousedragged(event1 -> {         point2d mouseinparent = c.localtoparent(event1.getx(), event1.gety());         c.setlayoutx(mouseinparent.getx() + dragdelta.getdragdeltax());         c.setlayouty(mouseinparent.gety() + dragdelta.getdragdeltay());     });      scene scene = new scene(root, 500, 500);      primarystage.setscene(scene);     primarystage.show(); }