ReDim 结构化数组

Question

我创建了一个有趣的结构“列表”。这些结构包含一些数组（动态），我想重新调整它们。但我收到一个错误：
    “在 3D Cube.exe 中发生了‘System.NullReferenceException’类型的第一次机会异常”和
    “对象引用未设置为对象的实例。”。
这就是代码的样子（你可以看到它看起来像 opengl）：

模块：

Public Module _3DDefinitions
    Public Pen1 As New System.Drawing.Pen(Color.White, 2)


    Public Structure VertexesObjects
        Dim Face() As Faces
        Dim FaceCount As Double
        Dim Position As DPoint  ''Translated Position
        Dim NPPF As Integer     ''NumberofPointsPerFace
    End Structure
    Public Structure Faces
        Dim PointVertexes() As _3DDefinitions.DPoint
        Dim PointCount As Double
        Dim FaceColor As Color
    End Structure
    Public Structure DPoint
        Dim X As Single
        Dim Y As Single
        Dim Z As Single
    End Structure

    Enum GL_LoadAction As Byte
        GL_Start = 1   ''Start- equivalent of GlBegin
        GL_End = 2     ''End-equivalent of GlEnd 
    End Enum

    Enum GL_EnableAction As Byte
        GL_UseDefaultUnit = 1
        GL_UseOwnUnit = 2
        GL_Translation = 4
    End Enum
End Module

类（我没有包括类的第一部分以及许多子类和函数）：

Private Objects() As _3DDefinitions.VertexesObjects,
    ObjectsIndex As Double, FacesIndex As Double, PointsIndex As Double,
    GL_NPPF As Integer = 4, GL_COLOR As Color = Color.Brown,
    GL_Status As _3DDefinitions.GL_LoadAction = GL_LoadAction.GL_Start, GL_TranslatePosition As _3DDefinitions.DPoint,
    GL_Settings As _3DDefinitions.GL_EnableAction = GL_EnableAction.GL_UseDefaultUnit,
    GL_DrawingInitialized As Boolean = False, GL_GraphicsInitialized As Boolean = False,
    GL_Unit As Double = 300


Public Sub GL_LoadVertexes(ByVal Operation As _3DDefinitions.GL_LoadAction)
    GL_Status = Operation
    If Operation = _3DDefinitions.GL_LoadAction.GL_Start And Not GL_DrawingInitialized Then
        GL_DrawingInitialized = True
        GL_GraphicsInitialized = False

        ReDim Preserve Objects(ObjectsIndex)

        FacesIndex = 0
        PointsIndex = 0

    ElseIf Operation = GL_LoadAction.GL_End And GL_GraphicsInitialized And GL_DrawingInitialized Then
        GL_DrawingInitialized = False
        ObjectsIndex = ObjectsIndex + 1

        Draw()

    End If
End Sub

Public Sub LoadVertex3D(ByVal X As Single, ByVal Y As Single, ByVal Z As Single)

    If GL_Status = GL_LoadAction.GL_Start Then
        GL_GraphicsInitialized = True

        ReDim Preserve Objects(ObjectsIndex).Face(FacesIndex).PointVertexes(PointsIndex)''<--Here is the error

        If FindBit(GL_Settings, GL_EnableAction.GL_UseOwnUnit) Then
            With Objects(ObjectsIndex).Face(FacesIndex).PointVertexes(PointsIndex)
                .X = X
                .Y = Y
                .Z = Z
            End With

        ElseIf FindBit(GL_Settings, GL_EnableAction.GL_UseDefaultUnit) Then
            With Objects(ObjectsIndex).Face(FacesIndex).PointVertexes(PointsIndex)
                .X = X * GL_Unit / 10
                .Y = Y * GL_Unit / 10
                .Z = Z * GL_Unit / 10
            End With

        End If

        If PointsIndex = GL_NPPF - 1 Then
            FacesIndex = FacesIndex + 1
            PointsIndex = 0
        Else

            PointsIndex = PointsIndex + 1

        End If

    End If
End Sub

子 LoadVertex3D 只是加载内存中的一些点（坐标）（使用结构），子 GL_LoadVertexes 告诉类用户想要加载 3d 对象的点.我真的需要这些结构，因为例如我想创建一个新的“对象”，所以我必须再次使用“对象”特殊变量。但是当我这样做时，FacesIndex 和 PointsIndex（它们只是计数器）将被重置。
      唯一保持不变的变量是 ObjectsIndex。这就是为什么我需要这些结构，因为在这些结构中我可以保存创建的面和点的数量（在 FaceCount 和 PointCount 变量中）。
       有什么问题？或者如果您知道更好的解决方案来满足我的需求，可以告诉我吗？

Answer 1

你的问题真的在这里：

FacesIndex = FacesIndex + 1

您增加索引而不对其引用的数组进行 redim。然后，当您重新调整您的PointVertexes 数组时，您将获得空引用，因为Face 数组中不存在索引。要解决此问题，您应该执行以下操作：

    If PointsIndex = GL_NPPF - 1 Then
        FacesIndex = FacesIndex + 1
        ReDim Preserve Objects(ObjectsIndex).Face(FacesIndex)
        PointsIndex = 0
        ... and then create the inner array, etc...