[Ikvm-developers] NoClassDefFoundError occurred

[Frank B. <fbergman@u.washington.edu>]

Hello, 

First of all let me say how much I appreciate all the hard work you do with
ikvm it is simply amazing and has changed the way we will deploy our
software from now on. However, I am facing problems and it would be great if
you could help me out. 

I'm using ikvmc generated assemblies that allow me to access the qtjambi
framework:

http://code.google.com/p/qt4dotnet/

and mostly things work just fine, at least as long as I confine myself to
never use .Net objects in a class used by qtjambi. However for my current
project I'm stumped. I need to define my own object inherited from
QGraphicsScene, which works great up to the point where qtjambi is using it
(here in a custom QGraphicsItem::itemChange method). So I was hoping you
could tell me what I could do to make it work. I think I saw on the IKVM
website that it should be possible to refer to CLI objects. Here the error I
get: 


public class MyItem: QGraphicsItemGroup
{
public override object itemChange(QGraphicsItem.GraphicsItemChange change,
object value)
        {
            if (change ==
QGraphicsItem.GraphicsItemChange.ItemPositionChange)
            {
                UpdateTheItem();

                return value;
            }

            return base.itemChange(change, value); //<---- BOOOOM
        }

....
}

The Exception: 

Java.lang.NoClassDefFoundError {"cli/MyGraphicsScene"}

   at IKVM.Runtime.JNI.Frame.Leave()
   at
com.trolltech.qt.gui.QGraphicsItemGroup.__qt_itemChange_GraphicsItemChange_O
bject(Int64 , Int32 , Object )
   at com.trolltech.qt.gui.QGraphicsItemGroup.itemChange(GraphicsItemChange
change, Object value)
   at BenZaiTenQt.GraphicItems.QSpeciesItem.itemChange(GraphicsItemChange
change, Object value) in MyItem.cs:line 167


and here the definition of the scene: 

public class MyGraphicsScene : QGraphicsScene
    {
        
        
        public MyGraphicsScene(QObject parent)
            : base(parent)
        {
            Initialize();
        }
        public MyGraphicsScene(QRectF sceneRect, QObject parent)
            : base(sceneRect, parent)
        {
            Initialize();
        }
        public MyGraphicsScene(double x, double y, double width, double
height, QObject parent)
            : base(x, y, width, height, parent)
        {
            Initialize();
        }
        public MyGraphicsScene(QRectF sceneRect)
            : base(sceneRect)
        {
            Initialize();
        }
        public MyGraphicsScene(double x, double y, double width, double
height)
            : base(x, y, width, height)
        {
            Initialize();
        }
        protected internal MyGraphicsScene(QtJambiObject.QPrivateConstructor
p)
            : base(p)
        {
            Initialize();
        }

        private void Initialize()
        {
            
        }
         
    }

Also things like the following seem to fail, I wonder why: 

public class MyVeryImportantClass { public MyVeryImportantClass () {} } 

public class MyDialog : QDialog { public MyDialog(MyVeryImportantClass var1)
{ _var1 = var1; } 
		public MyVeryImportantClass Helper { get { return _var1; }
set { _var1 = value;} } }

where a CLI class is referenced will just fail with a
NullReferenceException:

*** exception in native code ***
System.NullReferenceException: Object reference not set to an instance of an
object.
   at __<Getter>(Object )
   at
IKVM.NativeCode.sun.reflect.ReflectionFactory.FieldAccessorImplBase.FastObje
ctFieldAccessor.get(Object obj)
   at IKVM.Runtime.JNIEnv.GetObjectField(JNIEnv* pEnv, IntPtr obj, IntPtr
fieldID)
   at com.trolltech.qt.gui.QDialog.__qt_QDialog_QWidget_WindowFlags(Int64 ,
Int32 )
*** exception in native code ***
System.NullReferenceException: Object reference not set to an instance of an
object.
   at __<Getter>(Object )
   at
IKVM.NativeCode.sun.reflect.ReflectionFactory.FieldAccessorImplBase.FastObje
ctFieldAccessor.get(Object obj)
   at IKVM.Runtime.JNIEnv.GetObjectField(JNIEnv* pEnv, IntPtr obj, IntPtr
fieldID)
   at com.trolltech.qt.core.QObject.__qt_toString(Int64 )


Thank you so much 
Best
frank