java - JMapViewer, MouseListener called 2 times -

working jmapviewer, strange behavior of component recognized. using defaultmapcontroller map position (lat, lon).

import java.awt.graphics; import java.awt.point; import java.awt.event.mouseadapter; import java.awt.event.mouseevent; import javax.swing.jframe; import org.openstreetmap.gui.jmapviewer.defaultmapcontroller; import org.openstreetmap.gui.jmapviewer.jmapviewer;  public class test extends jmapviewer{  public test()  {     addmouselistener(new defaultmapcontroller(this) {             public void mouseclicked(mouseevent e){             point  start = e.getpoint();             system.out.println(e.getpoint());             }                    });   }  protected void paintcomponent(graphics g){super.paintcomponent(g);}    public static void main (string [] args){             jframe jf = new jframe();             jf.setsize(800, 600);             test t= new test();             jf.add(t);             jf.setvisible(true);     } } 

running code, after left mouse button pressed, method mouseclicked() gets called multiple times (2x). after replacement

    addmouselistener(new defaultmapcontroller(this) { 

with

    addmouselistener(new mouseadapter() { 

the code works correctly, method gets called 1x. problem? bug inside library or syntax wrong or unsafe? how avoid issue? help.

your test extends jmapviewer, adding mouselistener in instance initializer block. consequence, "default constructor call no-argument constructor of superclass." superclass, jmapcontroller, adds mouselistener—you guessed it—a second time.

public jmapcontroller(jmapviewer map) {     this.map = map;     if (this instanceof mouselistener)         map.addmouselistener((mouselistener) this);     … } 

instead, create new jmapcontroller or defaultmapcontroller, shown here, , use construct jmapviewer.

import java.awt.eventqueue; import java.awt.event.mouseevent; import javax.swing.jframe; import org.openstreetmap.gui.jmapviewer.defaultmapcontroller; import org.openstreetmap.gui.jmapviewer.jmapviewer;  /**  * @see https://stackoverflow.com/a/39461854/230513  */ public class testmapcontroller {      private void display() {         jframe f = new jframe("testmapcontroller");         f.setdefaultcloseoperation(jframe.exit_on_close);         jmapviewer map = new jmapviewer();         new defaultmapcontroller(map) {             @override             public void mouseclicked(mouseevent e) {                 system.out.println(e.getpoint());             }         };         f.add(map);         f.pack();         f.setlocationrelativeto(null);         f.setvisible(true);     }      public static void main(string[] args) {         eventqueue.invokelater(new testmapcontroller()::display);     } }