Chapter 14, p483

ozPATT · September 21st, 2005, 03:30 AM

Hello!

Quick question.. I have been working through this book - I think it is really brialliant! - but I am getting an error that I can't solve on the above mentioned page. Your code says:

Code:

Else
            'display the color dialog
            If dlgColor.ShowDialog = DialogResult.OK Then
                'add the new color
                AddColor(dlgColor.Color)
                'resize the palette to show the dialog
                OnResize(New EventArgs)
            End If
        End If

I have put this in, and when I run the problem, I can left click, right click, and draw no problems. When I click on the background to add a custom colour though, I get the following error...

Quote:

quote:An unhandled exception of type 'System.NullReferenceException' occurred in PatrickPaint.exe

Additional information: Object reference not set to an instance of an object.

my full code is as follows: (hope this is ok to post it...)

Code:

Protected Overrides Sub OnMouseUp(ByVal e As System.Windows.Forms.MouseEventArgs)
        'find the button we clicked on
        Dim button As ColorPaletteButton = GetButtonAt(e.X, e.Y)
        If Not button Is Nothing Then
            'select this color
            If e.Button = MouseButtons.Left Then
                'make sure this button is not the current right
                If Not button Is rightButton Then
                    'set the color
                    LeftColor = button.Color
                    'clear the existing selection
                    If Not leftButton Is Nothing Then leftButton.ButtonAssignment = _
                        ColorPaletteButton.ButtonAssignments.None
                    Invalidate(leftButton.Rectangle)
                End If
                'mark the button
                button.ButtonAssignment = ColorPaletteButton.ButtonAssignments.LeftButton
                Invalidate(button.Rectangle)
                leftButton = button
                'fire the event
                RaiseEvent LeftClick(Me, New EventArgs)
            End If
            'did we click with the right?
            If e.Button = MouseButtons.Right Then
                'make sure the button is not the current left
                If Not button Is leftButton Then
                    'set right colour
                    RightColor = button.Color
                    'clear the existing selection
                    If Not rightButton Is Nothing Then
                        rightButton.ButtonAssignment = _
                            ColorPaletteButton.ButtonAssignments.None
                        Invalidate(rightButton.Rectangle)
                    End If
                    'mark the button
                    button.ButtonAssignment = ColorPaletteButton.ButtonAssignments.RightButton
                    Invalidate(button.Rectangle)
                    rightButton = button
                    'fire the event
                    RaiseEvent RightClick(Me, New EventArgs)
                End If
            End If
        Else
            'display the color dialog
            If dlgColor.ShowDialog = DialogResult.OK Then
                'add the new color
                AddColor(dlgColor.Color)
                'resize the palette to show the dialog
                OnResize(New EventArgs)
            End If
        End If
    End Sub

could someone let me know what I am doing wrong here?

Thanks

Patrick

Visit my site: http://www.drybonesuk.com

Thearon · October 30th, 2005, 10:25 PM

Patrick,

Have you downloaded the code for the book and try to run this program? Have you compared your code against the sample downloaded code? Try these two things and see if it doesn't help.

Thearon