制作洪水填充动画 vb return object is currently used elsewhere using thread.sleep

Question

我尝试在 vb 中使用睡眠制作动画洪水填充（扫描线算法）。所以它会显示像素被着色的顺序。它会工作一点点，但随后会 return object is currently used elshere

这是我的代码

Sub AnimatedRFRecursive(ByVal P As Point, ByVal C0 As Color, ByVal C1 As Color)

    Dim i, xL, xR As Integer
    Dim a As Point
    i = P.X
    While (i >= 0 AndAlso BMP.GetPixel(i, P.Y) = C0)
        Thread.Sleep(10)
        BMP.SetPixel(i, P.Y, C1)
        PictureBox1.Invoke(New Action(Sub() PictureBox1.Image = BMP))
        i -= 1
    End While
    xL = i + 1
    i = P.X + 1
    While (i < 500 AndAlso BMP.GetPixel(i, P.Y) = C0)
        Thread.Sleep(10)
        BMP.SetPixel(i, P.Y, C1)
        PictureBox1.Invoke(New Action(Sub() PictureBox1.Image = BMP))
    End While
    xR = i - 1
    For i = xL To xR
        If (P.Y < 349 AndAlso BMP.GetPixel(i, P.Y + 1) = C0) Then
            a.X = i
            a.Y = P.Y + 1

            AnimatedRFRecursive(a, C0, C1)
        End If
        If (P.Y > 0 AndAlso BMP.GetPixel(i, P.Y - 1) = C0) Then
            a.X = i
            a.Y = P.Y - 1
            AnimatedRFRecursive(a, C0, C1)
        End If
    Next
End Sub

我是这样称呼它的

Dim thr As New Threading.Thread(Sub() AnimatedRFRecursive(point, C, Color))
thr.Start()

请告诉我我哪里做错了，或者如果你有任何其他有效的方法也可以。谢谢

Answer 1

您有多个线程需要访问同一个对象 (BMP)。这将要求您同步对 BMP 对象的访问。

请注意，您的原始代码有两个幻数（500 和 349），我假设它们对应于位图的宽度和高度。如果此假设不正确，请更改以下代码中变量的用法。

Private BMP As Bitmap
Private BMPKey As New Object
Private Sub UpdatePictureBox()
    PictureBox1.Invoke(Sub()
                                SyncLock BMPKey
                                    Dim oldBM As Image = PictureBox1.Image
                                    PictureBox1.Image = New Bitmap(BMP)
                                    If oldBM IsNot Nothing Then oldBM.Dispose()
                                End SyncLock

                                End Sub)

End Sub

Private Function GetBMPPixel(x As Int32, y As Int32) As Color
    SyncLock BMPKey
        Return BMP.GetPixel(x, y)
    End SyncLock
End Function

Private Sub SetBMPPixel(x As Int32, y As Int32, c As Color)
    SyncLock BMPKey
        BMP.SetPixel(x, y, c)
    End SyncLock
End Sub

Sub AnimatedRFRecursive(ByVal P As Point, ByVal C0 As Color, ByVal C1 As Color)

     Dim i, xL, xR As Integer
     Dim a As Point
     i = P.X
     Dim width As Int32
     Dim height As Int32
     SyncLock BMPKey
        width = BMP.Width       ' original code magic number of 500 
        height = BMP.Height ' original code magic number of 349  
     End SyncLock
     While (i >= 0 AndAlso GetBMPPixel(i, P.Y).ToArgb = C0.ToArgb)
          Thread.Sleep(10)
          SetBMPPixel(i, P.Y, C1)
          UpdatePictureBox()
          i -= 1
     End While
     xL = i + 1
     i = P.X + 1
     While (i < width - 1 AndAlso GetBMPPixel(i, P.Y).ToArgb = C0.ToArgb)
          Thread.Sleep(10)
          SetBMPPixel(i, P.Y, C1)
          UpdatePictureBox()
     End While
     xR = i - 1
     For i = xL To xR
          If (P.Y < height - 1 AndAlso GetBMPPixel(i, P.Y + 1).ToArgb = C0.ToArgb) Then
                a.X = i
                a.Y = P.Y + 1

                AnimatedRFRecursive(a, C0, C1)
          End If
          If (P.Y > 0 AndAlso GetBMPPixel(i, P.Y - 1).ToArgb = C0.ToArgb) Then
                a.X = i
                a.Y = P.Y - 1
                AnimatedRFRecursive(a, C0, C1)
          End If
     Next
End Sub

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