NullReferenceException in my Project

Hey guys,

At first, sorry for my English, I am German ;).
So, concering my project: I am trying to control an RC Car via Kinect, until now I got it working with key control only (eg WASD). So, I am using a Velleman K8055 Interface Board + the Kinect and VB Windows Forms. So far, so good, I created 4 Forms: menu, info, kinect-controls + wasdcontrols window. The error only occurs for my kinect-controls window (german name: Steuerung.vb) & that's my source code:

Code:

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Imports Microsoft.Research.Kinect.Nui
Imports System.Text
Imports Coding4Fun.Kinect.WinForm
Imports System.Xml.Serialization
Imports System.IO





Public Class Steuerung

    Private Pointer = PictureBox2
    Private Declare Function OpenDevice Lib "k8055d.dll" (ByVal CardAddress As Integer) As Integer
    Private Declare Function CloseDevice Lib "k8055d.dll" (ByVal CardAddress As Integer) As Integer
    Private Declare Sub SetDigitalChannel Lib "k8055d.dll" (ByVal Channel As Integer)
    Private Declare Sub ClearAllDigital Lib "k8055d.dll" (ByVal Channel As Integer)
    Private Declare Sub ClearDigitalChannel Lib "k8055d.dll" (ByVal Channel As Integer)
    Dim nui As New Runtime()





    Public Sub New()

        InitializeComponent()

    End Sub

    Private Sub Window_Loaded(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load


        nui.Initialize(RuntimeOptions.UseSkeletalTracking)
        SetupKinect()
        AddHandler nui.SkeletonFrameReady, AddressOf nui_SkeletonFrameReady
        AddHandler Runtime.Kinects.StatusChanged, AddressOf Kinects_StatusChanged
 End Sub       
    Private Sub SetupKinect()
        If Runtime.Kinects.Count = 0 Then
            Label2.Text = "Keine Kinect angeschlossen"
        Else
            'use first Kinect
            nui = Runtime.Kinects(0)
            nui.Initialize(RuntimeOptions.UseColor Or RuntimeOptions.UseDepthAndPlayerIndex Or RuntimeOptions.UseSkeletalTracking)
        End If
    End Sub
    Private Sub Kinects_StatusChanged(sender As Object, e As StatusChangedEventArgs)
        Dim message As String = "Status geändert: "
        Select Case e.Status
            Case KinectStatus.Connected
                message += "Verbunden"
                Exit Select
            Case KinectStatus.Disconnected
                message += "Getrennt"
                Exit Select
            Case KinectStatus.[Error]
                message += "Error"
                Exit Select
            Case KinectStatus.NotPowered
                message += "Keine Stromversorgung"
                Exit Select
            Case KinectStatus.NotReady
                message += "Nicht bereit"
                Exit Select
            Case Else
                If e.Status.HasFlag(KinectStatus.[Error]) Then
                    message += "Kinect Error"
                End If
                Exit Select
        End Select
        Label2.Text = message


    End Sub

   

    Private Sub nui_SkeletonFrameReady(ByVal sender As Object, ByVal e As SkeletonFrameReadyEventArgs)

        Dim allSkeletons As SkeletonFrame = e.SkeletonFrame

        Dim skeleton As SkeletonData = ( _
            From s In allSkeletons.Skeletons _
            Where s.TrackingState = SkeletonTrackingState.Tracked _
            Select s).FirstOrDefault()




        Dim HandRight = skeleton.Joints(JointID.HandRight).ScaleTo(320, 240, 0.5F, 0.5F)



        SetEllipsePosition(skeleton.Joints(JointID.HandRight))
    End Sub

    Private Sub SetEllipsePosition(ByVal joint As Joint)
        Dim scaledJoint = joint.ScaleTo(320, 240, 0.5F, 0.5F)

        PictureBox2.Left = scaledJoint.Position.X
        PictureBox2.Top = scaledJoint.Position.Y
    End Sub



    Private Sub Hauptmenübutton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Hauptmenübutton.Click
        Hauptmenü.Show()
        nui.Uninitialize()

        Label1.Text = "Nicht verbunden"

        Me.Hide()



    End Sub

    Private Sub Infobutton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Infobutton.Click
        Info.Show()
        Me.Hide()

    End Sub

    Private Sub Verbindenbutton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Verbindenbutton.Click
        Dim CardAddress As Integer
        Dim h As Integer
        CardAddress = 2

        h = OpenDevice(2)
        Label1.Text = "Karte " + Str(h) + " angeschlossen"
    End Sub



End Class

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So, my error is concerning this line in the bottom third:

Code:

---

Dim HandRight = skeleton.Joints(JointID.HandRight).ScaleTo(320, 240, 0.5F, 0.5F)

---

and it says:

NullReferenceException [wurde nicht von Benutzercode behandelt.] (means: unhandled by user code.)
Object reference not set to an instance of an object.

What I tried so far:

1) Re-creating & cleaning up my project files (was promised to be the solution when I googled this)
2) Defining Dim HandRight in my Declarations
3) Setting HandRight to "Nothing"

but however, nothing will help :/
By the way, I am using the Coding4Fun.Kinect.WinForm.dll & the Microsoft.Research.Kinect.dll


If I forgot to mention anything important, please tell me.


Kind regards,

alex

:wave:
If I'm understanding the question right...

It could be either the skeleton object or the skeleton.Joints(JointID.HandRight) object that are null references, or 'Nothing' as they are referred to in VB. When the code breaks at that line, highlight those objects and right click and choose 'immediate watch'. Once you know which object is null, then you'll have a better idea of what to do to fix it.

I think I can now say this error is definitely caused by skeleton.Joints(JointID.HandRight), immediate watch tells me the following

Code:

---

                HandRight = skeleton.Joints(JointID.HandRight)        Der =-Operator ist für die Typen "Microsoft.Research.Kinect.Nui.Joint" und "Microsoft.Research.Kinect.Nui.Joint" nicht definiert.

---

which means something like

Code:

---

The =-operator is not defined for type "Microsoft.Research.Kinect.Nui.Joint" and "Microsoft.Research.Kinect.Nui.Joint".

---

. Because this is the only line containing an error I would conclude that this is what causes my problem.. But what can I do to fix this? Sorry, but I am quite new to Visual Basic :/ If this says that for Microsoft.Research.Kinect.Nui.Joint I cannot use "=-", I do not know why this error occurs because I have not even once used this.

Thanks for your patience ;)


Kind regards,


alex

I'm confused. From the code it appears it's using the "=" operator, not the "=-" operator. I know why it would give you that error if you used it. That operator is a mathematical assignment operator - used to subtract one number from an existing number. For example:

Code:

---

Dim X as integer = 4

X =- 1

'X now equals 3

---

But it makes no sense to try to subtract an object from an object.

When you get this error, examine each object in turn. In that line, there are only a few of them:

1) HandRight, but this can't cause the error.
2) skeleton
3) skeleton.Joints(JointID.HandRight)

To examine them, highlight each in turn and press Shift+F9. One of them is Nothing, and that one is your problem. That's always the first step for the original error message. Once you determine which one is Nothing (it sounds like it is the third one, in this case), then the next step is to figure out why that is Nothing.

In that case, it appears like skeleton.Joints is a method that takes an identifier and returns an object (probably an object of type joint, but I don't know kinect). The object is nothing, which suggests that there isn't a joint with the identifier JointID.RightHand. So why not? I'm not sure that any of us can say.

Is it possible that the particular item shouldn't exist in the setting you are working with?

Ok, I now applied the immediate watch on skeleton.Joints only and the following came up confirming your statement that this is null.

Code:

---

                skeleton.Joints        Das referenzierte skeleton-Objekt hat den Wert "Nothing".        Microsoft.Research.Kinect.Nui.JointsCollection

---

means

Code:

---

skeleton.Joints    The referenced skeleton-object has the value "Nothing". Microsoft.Research.Kinect.Nui.JointsCollection

---

Quote:

---

Is it possible that the particular item shouldn't exist in the setting you are working with?

---

I think it should, but I am not completely sure about this. I found big fragments of this code here and used them for this program.

But as they are working in c sharp/ vb wpf I don't exactly know if this will work out for WinForms...


Kind regards,


alex