將項目添加到列表時出錯

Question

我正在嘗試使用vb制作游戲，所以我開設了此類：

    Imports Microsoft.VisualBasic.PowerPacks
    Module EntityI
    Public entities As List(Of Entity)
    Public Function getEntity(ByVal uuid As Guid) As Entity
    For i = 0 To entities.Count - 1
        If entities.Item(i).getUUID = uuid Then
            Return entities.Item(i)
        End If
    Next
    Return Nothing
End Function
    End Module
    Public Class Entity
Private uuid As Guid
Private location As Location
Private shape As OvalShape

Public Sub New()
    uuid = System.Guid.NewGuid
    Dim canvas As New PowerPacks.ShapeContainer
    canvas.Parent = Game
    shape = New OvalShape With {.Parent = canvas}
    shape.SetBounds(50, 50, 50, 50)
    save()
End Sub
Public Function getUUID() As Guid
    Return uuid
End Function
Public Function getLocation() As Location
    Return location
End Function
Public Sub teleport(ByVal location As Location)
    Me.location = location
End Sub
Private Sub save()
entities.add(Me)
End Sub
End Class

因此，這會在entities.add（Me）（NullRefernceException）處產生錯誤。 列表中有其他內容嗎？ 請幫助。

Answer 1

你需要

Public entities As New List(Of Entity)

Answer 2

您是新名單。 您僅將變量聲明為列表。 將Public entities As List(Of Entity)更改為Public entities As New List(Of Entity)