java - NullPointerException during writeObject() while using Nimbus Look and Feel -
i have 4 classes: testgui, mainmenubar, mainframe , projecttoadd. mainframe , projecttoadd implements serializable. when click on new>project in mainmenubar want create new project, new dir , in dir write serializable object. when object has been writen nullpointerexception (see stacktrace @ end). if remove , feel part of code in main method not error more... i'm using netbeans ide 8.0.2.
testgui code:
package testgui; import javax.swing.uimanager; import javax.swing.uimanager.lookandfeelinfo; public class riskmanagergui { public static void main(string[] args) { java.awt.eventqueue.invokelater(new runnable() { public void run() { try { (lookandfeelinfo info : uimanager.getinstalledlookandfeels()) { if ("nimbus".equals(info.getname())) { uimanager.setlookandfeel(info.getclassname()); break; } } } catch (exception e) { // if nimbus not available, fall cross-platform try { uimanager.setlookandfeel(uimanager.getcrossplatformlookandfeelclassname()); } catch (exception ex) { // not worth time } } new mainframe().setvisible(true); } }); } } mainmenubar code:
package menu_package; import java.awt.event.actionevent; import java.awt.event.actionlistener; import javax.swing.*; import testgui.mainframe; public class mainmenubar extends jmenubar{ private mainframe mainframe; public mainmenubar(mainframe mainframe){ this.mainframe = mainframe; jmenu filemenu = new jmenu("file"); jmenu newmenu = new jmenu("new"); jmenuitem projectmenuitem = new jmenuitem("project"); projectmenuitem.addactionlistener(new addnewproject()); newmenu.add(projectmenuitem); filemenu.add(newmenu); add(filemenu); } class addnewproject implements actionlistener { public void actionperformed(actionevent event) { mainframe.addnewproject(); } } } mainframe code:
package testgui; import java.awt.*; import java.io.file; import java.io.fileoutputstream; import java.io.ioexception; import java.io.objectoutputstream; import java.io.serializable; import java.util.arraylist; import javax.swing.*; import javax.swing.border.*; import left_panel_package.projectsjtree; import menu_package.mainmenubar; public class mainframe extends jframe implements serializable{ private string instalationlocation; private arraylist <projecttoadd> listofprojects; public mainframe(){ initcomponents(); } public void initcomponents() { setinstalationlocation("c:\\users\\pera\\desktop\\riskmanagergui"); listofprojects = new arraylist<projecttoadd>(); setdefaultcloseoperation(javax.swing.windowconstants.exit_on_close); settitle("test"); setname("mainframe"); jpanel mainpanel = new jpanel(); setcontentpane(mainpanel); setjmenubar(new mainmenubar(this)); graphicsdevice gd = graphicsenvironment.getlocalgraphicsenvironment().getdefaultscreendevice(); int width = gd.getdisplaymode().getwidth(); int height = gd.getdisplaymode().getheight(); setsize(width, height); setlocationrelativeto(null); } public string getinstalationlocation() { return instalationlocation; } private void setinstalationlocation(string instalationlocation) { this.instalationlocation = instalationlocation; } public void addnewproject(){ string nameofproject = joptionpane.showinputdialog(null, "enter name of new project: ", "add new project",joptionpane.ok_cancel_option); if ((nameofproject != null) && (nameofproject.length() > 0)) { try { projecttoadd newproject = new projecttoadd(this, nameofproject); listofprojects.add(newproject); file thedir = new file(newproject.getprojectpath()); thedir.mkdirs(); newproject.writetofile(); } catch (ioexception ex) { system.out.println(ex.getmessage()); } } } } projecttoadd code:
package testgui; import java.io.fileoutputstream; import java.io.ioexception; import java.io.objectoutputstream; import java.io.serializable; public class projecttoadd implements serializable{ private string nameofproject; private mainframe mainframe; private string projectpath; public projecttoadd (mainframe mainframe, string nameofproject) { this.mainframe = mainframe; setnameofproject(nameofproject); setprojectpath(mainframe.getinstalationlocation()+"\\projects\\"+nameofproject); } public string getnameofproject() { return nameofproject; } public void setnameofproject(string nameofproject) { this.nameofproject = nameofproject; } public void writetofile() throws ioexception{ objectoutputstream objectoutputstream = new objectoutputstream(new fileoutputstream(projectpath+ "\\"+nameofproject+".bin")); objectoutputstream.writeobject(this); } public void readfromfile(){ } public string getprojectpath() { return projectpath; } public void setprojectpath(string projectpath) { this.projectpath = projectpath; } } stack trace:
exception in thread "awt-eventqueue-0" java.lang.nullpointerexception @ javax.swing.plaf.synth.synthlookandfeel.paintregion(synthlookandfeel.java:371) @ javax.swing.plaf.synth.synthlookandfeel.update(synthlookandfeel.java:335) @ javax.swing.plaf.synth.synthrootpaneui.update(synthrootpaneui.java:119) @ javax.swing.jcomponent.paintcomponent(jcomponent.java:780) @ javax.swing.jcomponent.paint(jcomponent.java:1056) @ javax.swing.jcomponent.painttooffscreen(jcomponent.java:5210) @ javax.swing.repaintmanager$paintmanager.paintdoublebuffered(repaintmanager.java:1579) @ javax.swing.repaintmanager$paintmanager.paint(repaintmanager.java:1502) @ javax.swing.repaintmanager.paint(repaintmanager.java:1272) @ javax.swing.jcomponent._paintimmediately(jcomponent.java:5158) @ javax.swing.jcomponent.paintimmediately(jcomponent.java:4969) @ javax.swing.repaintmanager$4.run(repaintmanager.java:831) @ javax.swing.repaintmanager$4.run(repaintmanager.java:814) @ java.security.accesscontroller.doprivileged(native method) @ java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege(protectiondomain.java:76) @ javax.swing.repaintmanager.paintdirtyregions(repaintmanager.java:814) @ javax.swing.repaintmanager.paintdirtyregions(repaintmanager.java:789) @ javax.swing.repaintmanager.prepaintdirtyregions(repaintmanager.java:738) @ javax.swing.repaintmanager.access$1200(repaintmanager.java:64) @ javax.swing.repaintmanager$processingrunnable.run(repaintmanager.java:1732) @ java.awt.event.invocationevent.dispatch(invocationevent.java:311) @ java.awt.eventqueue.dispatcheventimpl(eventqueue.java:756) @ java.awt.eventqueue.access$500(eventqueue.java:97) @ java.awt.eventqueue$3.run(eventqueue.java:709) @ java.awt.eventqueue$3.run(eventqueue.java:703) @ java.security.accesscontroller.doprivileged(native method) @ java.security.protectiondomain$javasecurityaccessimpl.dointersectionprivilege(protectiondomain.java:76) @ java.awt.eventqueue.dispatchevent(eventqueue.java:726) @ java.awt.eventdispatchthread.pumponeeventforfilters(eventdispatchthread.java:201) @ java.awt.eventdispatchthread.pumpeventsforfilter(eventdispatchthread.java:116) @ java.awt.eventdispatchthread.pumpeventsforhierarchy(eventdispatchthread.java:105) @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:101) @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:93) @ java.awt.eventdispatchthread.run(eventdispatchthread.java:82)
the npe being thrown because you're trying serialize mainframe, object contains gui detritus, including nimbus l&f information, stuff shouldn't serialized , looks non-serializable. how know? mark field transient , see happens:
class projecttoadd implements serializable { private static final long serialversionuid = 1l; private string nameofproject; private transient mainframe mainframe; // ********** private string projectpath; if need serialize information that's held within mainframe, create non-gui model class contains key business data mainframe , serialize that, not view -- not gui itself. should in general never serialize view regardless, , it's idea refactor program logic out of view code.
and right, this:
objectoutputstream.writeobject(this); was related npe. apologies you.
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