I am constructing a quiz maker using NIfty. I begin by loading a basic question editor screen with:
nifty.fromXml(“Interface/questionEditorScreen.xml”, “questionEditor”, this);
nifty.gotoScreen(“questionEditor”);
In a previous version of my quiz maker, I successfully used the java builder code to generate my answer choice panels on the fly as needed. Recently while rewriting my application, I have gotten attached to using the Nifty-Editor v.1.0 which generates .xml files. I would like to dynamically add answer choice panels as needed by use via loading choice.xml template, giving it a unique id, then add it to my choicePanel. I tried but get NullPointerException with:
public void addChoice(){
nifty.addXml(“Interface/choice.xml”);
Element choice = nifty.getScreen(“choice”).findElementByName(“choicepanel”);
nextChoiceNum++;
choice.setId(“choice”+nextChoiceNum);
Element choicePanel = nifty.getScreen(“questionEditor”).findElementByName(“choicesPanel”);
choice.markForMove(choicePanel);
}
I also tried but get NullPointerException with:
public void addChoice(){
nifty.addXml(“Interface/choice.xml”);
Element choice = nifty.getScreen(“choice”).findElementByName(“choicepanel”);
nextChoiceNum++;
choice.setId(“choice”+nextChoiceNum);
Element choicePanel = nifty.getScreen(“questionEditor”).findElementByName(“choicesPanel”);
choice.add(choicePanel);
}
Where did I go wrong?
What is null? nifty? The screen? The element?
Thanks for the comment.
The output I get from:
public void addChoice(){
nifty.addXml(“Interface/choice.xml”);
Element choice = nifty.getScreen(“choice”).findElementByName(“choicepanel”);
nextChoiceNum++;
choice.setId(“choice”+nextChoiceNum);
Element choicePanel = nifty.getScreen(“questionEditor”).findElementByName(“choicesPanel”);
System.out.println(“The choice element is “+choice+”. The choicePanel element is “+choicePanel+”.”);
choice.markForMove(choicePanel);
}
is:
The choice element is choice1 (de.lessvoid.nifty.elements.Element@b788e5). The choicePanel element is choicesPanel (de.lessvoid.nifty.elements.Element@17caa26).
Dec 06, 2012 5:36:58 PM com.jme3.app.Application handleError
SEVERE: Uncaught exception thrown in Thread[LWJGL Renderer Thread,5,main]
java.lang.NullPointerException
at de.lessvoid.nifty.Nifty$ElementMoveAction.perform(Nifty.java:1005)
at de.lessvoid.nifty.Nifty$EndOfFrameElementAction.perform(Nifty.java:1023)
at de.lessvoid.nifty.Nifty.executeEndOfFrameElementActions(Nifty.java:397)
at de.lessvoid.nifty.Nifty.handleDynamicElements(Nifty.java:316)
at de.lessvoid.nifty.Nifty.access$1500(Nifty.java:73)
at de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl.processEvent(Nifty.java:1371)
at de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl.processMouseEvent(Nifty.java:1329)
at com.jme3.niftygui.InputSystemJme.handleMouseEvent(InputSystemJme.java:124)
at com.jme3.niftygui.InputSystemJme.onMouseButtonEventQueued(InputSystemJme.java:196)
at com.jme3.niftygui.InputSystemJme.forwardEvents(InputSystemJme.java:260)
at de.lessvoid.nifty.Nifty.update(Nifty.java:248)
at com.jme3.niftygui.InputSystemJme.endInput(InputSystemJme.java:113)
at com.jme3.input.InputManager.processQueue(InputManager.java:821)
at com.jme3.input.InputManager.update(InputManager.java:885)
at com.jme3.app.Application.update(Application.java:606)
at com.jme3.app.SimpleApplication.update(SimpleApplication.java:230)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:151)
at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:185)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:228)
at java.lang.Thread.run(Thread.java:722)
The nifty, the screens and elements seem to all be non-Null. I’m confused.
I called the System.out just before
do you call [java]nifty.addXml("Interface/choice.xml");[/java] more than once, and is there a screencontroller definition in the xml file?
@wezrule
do you call
nifty.addXml(“Interface/choice.xml”);
more than once, and is there a screencontroller definition in the xml file?
No, I only call it once and there is a screencontroller assigned in the xml file.
What I did notice was the program seems to be in the process of loading the choice.xml file when the markForMove is called. Here is the verbose output.
(controller => fpl.GUIManager, id => choice)
children layers: 1
[element] (backgroundColor => #5500cc, childLayout => absolute, id => choice)
()
()
children elements: 1
[element] (style => nifty-panel-simple, name => choicepanel, imageMode => resize:9,2,9,9,9,2,9,2,9,2,9,9 {nifty-panel-simple}, id => choicepanel, width => 50%, y => 0, padding => 5px {nifty-panel-simple}, backgroundImage => panel/nifty-panel-simple.png {nifty-panel-simple}, x => 0, childLayout => absolute, height => 35px)
()
()
children elements: 2
[element] (style => nifty-textfield, name => textfield, id => textfield3, width => 90%, controller => de.lessvoid.nifty.controls.textfield.TextFieldControl, inputMapping => de.lessvoid.nifty.controls.textfield.TextFieldInputMapping, y => 0, focusable => true, x => 5, childLayout => overlay {nifty-textfield#panel}, height => 23px {nifty-textfield#panel})
(onClickMouseMove => onClickMouseMove(), onClick => onClick())
()
children elements: 2
[element] (backgroundColor => #666f {nifty-textfield#field}, childClip => true {nifty-textfield#field}, style => #field, childLayout => center {nifty-textfield#field}, visibleToMouse => true, padding => 0px,2px {nifty-textfield#field}, id => textfield3#field)
()
()
(name => changeMouseCursor, id => textFieldCursor)
()
(color => #822f, name => border, post => true)
The choice element is choice1 (de.lessvoid.nifty.elements.Element@1991731). The choicePanel element is choicesPanel (de.lessvoid.nifty.elements.Element@1c192c8).
()
(inset => 1px, color => #800f, name => colorBar, post => true)
(inset => 1px, color => #222f, name => border, post => true)
(name => renderQuad, post => true, length => 150, endColor => #2220, startColor => #2228)
(name => renderQuad, post => true, length => 150, endColor => #2228, startColor => #2220)
children elements: 1
[element] (style => #text, id => textfield3#field#text, textHAlign => left {nifty-textfield#text}, font => aurulent-sans-16.fnt {base-font}, color => #000f {nifty-textfield#text}, align => left {nifty-textfield#text}, selectionColor => #f00f {nifty-textfield#text}, valign => center {nifty-textfield#text}, visibleToMouse => false {nifty-textfield#text})
()
()
(color => #cccf, name => textColor, post => false)
no children elements
[element] (style => #cursor-panel, childLayout => absolute {nifty-textfield#cursor-panel}, padding => 0px,2px {nifty-textfield#cursor-panel})
()
()
children elements: 1
[element] (filename => textfield/cursor-empty.png {nifty-textfield#cursor}, style => #cursor, id => textfield3#cursor)
()
()
(filename => textfield/cursor.png, name => imageOverlayPulsate, post => true, timeType => infinite, pulsateType => rectangle, period => 250)
no children elements
[element] (style => nifty-checkbox-style, name => checkbox, width => 23px {nifty-checkbox-style#panel}, id => checkbox1, controller => de.lessvoid.nifty.controls.checkbox.CheckboxControl, y => 0, focusable => true, x => 364, visibleToMouse => true, childLayout => center {nifty-checkbox-style#panel}, backgroundColor => #666f {nifty-checkbox-style#panel}, height => 23px {nifty-checkbox-style#panel})
(onClick => onClick())
()
(color => #822f, name => border, post => true)
()
(inset => 1px, color => #800f, name => colorBar, post => true)
(inset => 1px, color => #222f, name => border, post => true)
(name => renderQuad, post => true, length => 150, endColor => #2220, startColor => #2228)
(name => renderQuad, post => true, length => 150, endColor => #2228, startColor => #2220)
children elements: 1
[element] (height => 32px {nifty-checkbox-style#select}, valign => center {nifty-checkbox-style#select}, style => #select, width => 32px {nifty-checkbox-style#select}, id => checkbox1#select, align => center {nifty-checkbox-style#select})
()
()
(startSize => 2.0, name => imageSize, post => true, length => 250, endSize => 1.0, customKey => show)
(end => #f, name => fade, post => true, length => 250, customKey => show, start => #0)
(height => 32px, neverStopRendering => true, filename => checkbox/checkbox.png, name => imageOverlay, post => true, width => 32px, customKey => show)
(end => #0, name => fade, post => true, length => 250, customKey => hide, start => #f)
(height => 32px, filename => checkbox/checkbox.png, name => imageOverlay, post => true, width => 32px, length => 250, customKey => hide)
(end => #f, name => fade, post => false, length => 150, start => #4)
(end => #4, name => fade, post => false, length => 150, start => #f)
no children elements
Dec 06, 2012 6:11:52 PM de.lessvoid.nifty.Nifty loadFromFile
INFO: loadFromFile took [64]
Dec 06, 2012 6:11:52 PM com.jme3.app.Application handleError
SEVERE: Uncaught exception thrown in Thread[LWJGL Renderer Thread,5,main]
java.lang.NullPointerException
at de.lessvoid.nifty.Nifty$ElementMoveAction.perform(Nifty.java:1005)
at de.lessvoid.nifty.Nifty$EndOfFrameElementAction.perform(Nifty.java:1023)
at de.lessvoid.nifty.Nifty.executeEndOfFrameElementActions(Nifty.java:397)
at de.lessvoid.nifty.Nifty.handleDynamicElements(Nifty.java:316)
at de.lessvoid.nifty.Nifty.access$1500(Nifty.java:73)
at de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl.processEvent(Nifty.java:1371)
at de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl.processMouseEvent(Nifty.java:1329)
at com.jme3.niftygui.InputSystemJme.handleMouseEvent(InputSystemJme.java:124)
at com.jme3.niftygui.InputSystemJme.onMouseButtonEventQueued(InputSystemJme.java:196)
at com.jme3.niftygui.InputSystemJme.forwardEvents(InputSystemJme.java:260)
at de.lessvoid.nifty.Nifty.update(Nifty.java:248)
at com.jme3.niftygui.InputSystemJme.endInput(InputSystemJme.java:113)
at com.jme3.input.InputManager.processQueue(InputManager.java:821)
at com.jme3.input.InputManager.update(InputManager.java:885)
at com.jme3.app.Application.update(Application.java:606)
at com.jme3.app.SimpleApplication.update(SimpleApplication.java:230)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:151)
at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:185)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:228)
at java.lang.Thread.run(Thread.java:722)
I just moved the:
[java]nifty.addXml("Interface/choice.xml");[/java]
out from addChoice() and ran it much earlier but still have the same error. 
I guess I’ll just go back to using the java builder methods for adding GUI components on user demand.
Nifty can break if its in the process of doing something, that’s where events/end notify can help. But when you call AddXML it will be loaded then and there, so that shouldn’t be an issue. When you call your function put a breakpoint in there and check that the state of nifty is how u expect. Current screen etc. Also do u not need a element.layout() after a move? I’ve not used it before.