Changing Screens in Nifty causes Exception

1

Hello, I can´t figure out how to make Nifty switch screens. My first screen is running fine and even the buttons do what they shall do, but whenever I attach the method “gotoScreen” or “fromXML” to a button, I get dozens of similar exceptions starting with “de.lessvoid.nifty.NiftyMethodInvoker callMethod
Warnung: Exception: java.lang.reflect.InvocationTargetException”

My current code looks like this:

       controller = new GUI_Controller(niftyDisplay, nifty);       
       stateManager.attach(controller);
             
    NiftyJmeDisplay niftyDisplay = new NiftyJmeDisplay(assetManager, inputManager, audioRenderer, guiViewPort);
    Nifty nifty = niftyDisplay.getNifty();
    guiViewPort.addProcessor(niftyDisplay);
    
        try {
        nifty.validateXml("Interface/xmltest.xml");
    } catch (Exception ex) {
        Logger.getLogger(GUI_Controller.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println("XML seems broken"); 
    }

    nifty.fromXml("Interface/xmltest.xml", "start", this.controller);

My XML looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<nifty xmlns="http://nifty-gui.sourceforge.net/nifty-1.3.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://nifty-gui.sourceforge.net/nifty-1.3.xsd http://nifty-gui.sourceforge.net/nifty-1.3.xsd">
  <useStyles filename="nifty-default-styles.xml" />
  <useControls filename="nifty-default-controls.xml" />

<screen id="start" controller="mygame.GUI_Controller">

        <layer id="background" childLayout="center">
            <panel id="panel_background" width = "50%" height="80%"  childLayout="vertical">

                <panel id="panel_top" backgroundColor="#ff0000ff" width="*" height="33%" childLayout="center">
                </panel>

                <panel id="panel_middle" backgroundColor="#1240abff" width="*" height="33%" childLayout="center">
                </panel>

                <panel id="panel_bottom" backgroundColor="#ffff00ff" width="*" height="*" childLayout="center">
                </panel>

            </panel>
        </layer>

        <layer id="foreground" childLayout="center">

   <panel id="panel_top" height="50%" width="50%" valign="center" childLayout="center">  
          <control name="button" label="Start Game" id="StartButton" align="center" valign="center" 
          visibleToMouse="true" > 
            <interact onClick="startGame()"/>
          </control>
        </panel>
         
   <panel id="panel_bottom" height="50%" width="50%" valign="bottom" childLayout="center">  
          <control name="button" label="Quit Game" id="QuitButton" align="center" valign="center" 
          visibleToMouse="true" > 
            <interact onClick="quitGame()"/>
          </control>
        </panel>    

       </layer>      

    </screen>
    </nifty>

Does anybody know what I am doing wrong? Do I maybe need to call other methods together with “gotoScreen” or “fromXML” to switch from one screen to another?

Thanks in advance!

2

Exceptions without a stack trace are almost totally useless, by the way.

3

Thanks, didnt´t know that. This is the output after pressing the switch-screen-button:

Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker callMethod
Warnung: Exception: java.lang.reflect.InvocationTargetException
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: sun.reflect.NativeMethodAccessorImpl invoke0 (NativeMethodAccessorImpl.java:-2)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: sun.reflect.NativeMethodAccessorImpl invoke (NativeMethodAccessorImpl.java:57)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: sun.reflect.DelegatingMethodAccessorImpl invoke (DelegatingMethodAccessorImpl.java:43)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: java.lang.reflect.Method invoke (Method.java:606)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.NiftyMethodInvoker callMethod (NiftyMethodInvoker.java:145)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.NiftyMethodInvoker performInvoke (NiftyMethodInvoker.java:104)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty$DelayedMethodInvoke perform (Nifty.java:1174)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty invokeMethods (Nifty.java:1152)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty handleDynamicElements (Nifty.java:354)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty access$1700 (Nifty.java:77)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl processEvent (Nifty.java:1374)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl processMouseEvent (Nifty.java:1329)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme handleMouseEvent (InputSystemJme.java:124)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme onMouseButtonEventQueued (InputSystemJme.java:232)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme forwardEvents (InputSystemJme.java:296)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty update (Nifty.java:288)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme endInput (InputSystemJme.java:113)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.input.InputManager processQueue (InputManager.java:819)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.input.InputManager update (InputManager.java:883)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.app.Application update (Application.java:604)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.app.SimpleApplication update (SimpleApplication.java:231)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.system.lwjgl.LwjglAbstractDisplay runLoop (LwjglAbstractDisplay.java:151)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.system.lwjgl.LwjglDisplay runLoop (LwjglDisplay.java:185)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.system.lwjgl.LwjglAbstractDisplay run (LwjglAbstractDisplay.java:228)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: java.lang.Thread run (Thread.java:744)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: Root Cause: java.lang.NullPointerException
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: mygame.GUI_Controller startGame (GUI_Controller.java:48)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: sun.reflect.NativeMethodAccessorImpl invoke0 (NativeMethodAccessorImpl.java:-2)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: sun.reflect.NativeMethodAccessorImpl invoke (NativeMethodAccessorImpl.java:57)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: sun.reflect.DelegatingMethodAccessorImpl invoke (DelegatingMethodAccessorImpl.java:43)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: java.lang.reflect.Method invoke (Method.java:606)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.NiftyMethodInvoker callMethod (NiftyMethodInvoker.java:145)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.NiftyMethodInvoker performInvoke (NiftyMethodInvoker.java:104)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty$DelayedMethodInvoke perform (Nifty.java:1174)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty invokeMethods (Nifty.java:1152)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty handleDynamicElements (Nifty.java:354)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty access$1700 (Nifty.java:77)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl processEvent (Nifty.java:1374)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty$NiftyInputConsumerImpl processMouseEvent (Nifty.java:1329)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme handleMouseEvent (InputSystemJme.java:124)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme onMouseButtonEventQueued (InputSystemJme.java:232)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme forwardEvents (InputSystemJme.java:296)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: de.lessvoid.nifty.Nifty update (Nifty.java:288)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.niftygui.InputSystemJme endInput (InputSystemJme.java:113)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.input.InputManager processQueue (InputManager.java:819)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.input.InputManager update (InputManager.java:883)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.app.Application update (Application.java:604)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.app.SimpleApplication update (SimpleApplication.java:231)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.system.lwjgl.LwjglAbstractDisplay runLoop (LwjglAbstractDisplay.java:151)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.system.lwjgl.LwjglDisplay runLoop (LwjglDisplay.java:185)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: com.jme3.system.lwjgl.LwjglAbstractDisplay run (LwjglAbstractDisplay.java:228)
Feb 18, 2016 10:41:56 AM de.lessvoid.nifty.NiftyMethodInvoker logException
Warnung: java.lang.Thread run (Thread.java:744)
BUILD SUCCESSFUL (total time: 7 seconds)
4

It’s your Code. You have to look through the code for a Root Cause and in this case it’s a NullPointerException in mygame.GUI_Controller.startGame() or Line 48.

Show us that Line or have a look at it. Nullpointer means you do something like “var.xyz” whereas var = null (Not defined (yet))

5

Line 48 just says: nifty.fromXml(“Interface/ingame.xml”, “ingame”);
Btw the “ingame.xml” is just an identical copy of the posted XML file with the title of the screen changed.
This is the code up to the start method:

  /*
     * To change this template, choose Tools | Templates
     * and open the template in the editor.
     */
    package mygame;
    
    import com.jme3.app.Application;
    import com.jme3.app.SimpleApplication;
    import com.jme3.app.state.AbstractAppState;
    import com.jme3.app.state.AppStateManager;
    import com.jme3.niftygui.NiftyJmeDisplay;
    import com.jme3.scene.Node;
    import de.lessvoid.nifty.Nifty;
    import de.lessvoid.nifty.builder.ScreenBuilder;
    import de.lessvoid.nifty.screen.Screen;
    import de.lessvoid.nifty.screen.ScreenController;
    import java.util.logging.Level;
    import java.util.logging.Logger;
    
    
    
    public class GUI_Controller extends AbstractAppState implements ScreenController {
     
        private SimpleApplication app;
     
        private Node x = new Node("x");  // some custom class fields...    
        public Node getX(){ return x; }  // some custom methods... 
        
        NiftyJmeDisplay niftyJmeDisplay;
        Nifty nifty;
        
       public GUI_Controller(NiftyJmeDisplay ni, Nifty nif){
    this.niftyJmeDisplay = ni;
    this.nifty = nif;
    }
       
       
            public void startGame() {
    
        System.out.println("Du haettest ins Spiel gewechselt"); 
        
        
     //  nifty.gotoScreen("ingame");  // switch to another screen
        //    Screen ingame = new ScreenBuilder("ingame") {{nifty.fromXml("Interface/ingame.xml", "ingame");}}.build(nifty);
        
          
      //TEST 
   nifty.fromXml("Interface/xmltest.xml", "ingame");
       
        // start the game and do some more stuff...
      }
6

The ‘nifty’ field is null if that’s the line throwing the NPE.

7

Then I guess nifty only uses the default (empty) constructor so keep a static “nifty” around :stuck_out_tongue:

8

Most likely this is caused be letting nifty create the screen controller for you instead of passing it in or registering it with nifty. But your class doesn’t have a no-arg constructor so there is no way that it could be creating that.

Best check the inputs to your constructor as the caller seems to be passing null.

9

It works now! I have been searching for ages, but I had never thought, that my mistake was that simple and obvious. Thanks a lot!

10

You’re welcome. That’s why stack traces are important as this time it told you exactly what the problem was.

It’s just a shame that nifty chooses to display exceptions in such an obnoxious way. The guys who wrote nifty are otherwise super-smart guys but this exception logging is just dumb.

11

Oh, and btw, NiftyJmeProcessor has a method that returns a Nifty. So, you can simply ask for a NiftyJmeDisplay in the constructor and get the Nifty object from it:

public GUI_Controller(NiftyJmeDisplay ni){
    this.niftyJmeDisplay = ni;
    this.nifty = niftyJmeDisplay.getNifty();
}
12

I had a discussion with them on their old site about the log format and logging in general - I know the logging has been changed in later versions of nifty so it might be better now. I haven’t actually checked but one can always hope :slight_smile: