VB.net透明控制问题

Question

Public Class HighlightKey
    Inherits Control
    Private m_fillColor As Color = Color.White
    Private m_opacity As Integer = 100
    Private alpha As Integer
    Private m_image As Image

    Public Sub New()

        SetStyle(ControlStyles.SupportsTransparentBackColor, True)
        SetStyle(ControlStyles.Opaque, True)
        Me.BackColor = Color.Transparent
        Console.WriteLine("new Highlight key ")
    End Sub

    Public Property Image() As Image
        Get
            Return m_image
        End Get
        Set(ByVal value As Image)
            m_image = value
        End Set
    End Property

    Protected Overloads Overrides ReadOnly Property CreateParams() As CreateParams
        Get
            Dim cp As CreateParams = MyBase.CreateParams
            cp.ExStyle = cp.ExStyle Or &H20
            Return cp
        End Get
    End Property

    Protected Overloads Overrides Sub OnBackColorChanged(ByVal e As EventArgs)
        If Me.Parent IsNot Nothing Then
            Parent.Invalidate(Me.Bounds, True)
        End If
        MyBase.OnBackColorChanged(e)
    End Sub

    Protected Overloads Overrides Sub OnParentBackColorChanged(ByVal e As EventArgs)
        Me.Invalidate()
        MyBase.OnParentBackColorChanged(e)
    End Sub


    Protected Overrides Sub OnPaintBackground(ByVal pevent As System.Windows.Forms.PaintEventArgs)
        MyBase.OnPaintBackground(pevent)
    End Sub

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)

        Dim g As Graphics = e.Graphics
        Dim brush As New SolidBrush(Me.ForeColor)
        Dim StringSize As New SizeF

        alpha = (m_opacity * 255) / 100

        If m_image IsNot Nothing Then
            StringSize = g.MeasureString(Me.Text, Me.Font)
            Dim x As Integer = (CInt(Me.m_image.Width) - CInt(StringSize.Width)) / 2
            g.DrawImage(m_image, 0, 0, m_image.Width, m_image.Height)
            g.DrawString(Me.Text, Me.Font, brush, x, 20)
        End If

        brush.Dispose()
        g.Dispose()
        MyBase.OnPaint(e)
    End Sub

    Public Function SetImgOpacity(ByVal imgPic As Image, ByVal imgOpac As Single) As Image


        Dim bmpPic As New Bitmap(imgPic.Width, imgPic.Height)

        Dim gfxPic As Graphics = Graphics.FromImage(bmpPic)

        Dim cmxPic As New ColorMatrix()
        cmxPic.Matrix33 = imgOpac

        Dim iaPic As New ImageAttributes()
        iaPic.SetColorMatrix(cmxPic, ColorMatrixFlag.[Default], ColorAdjustType.Bitmap)

        gfxPic.DrawImage(imgPic, New Rectangle(0, 0, bmpPic.Width, bmpPic.Height), 0, 0, imgPic.Width, imgPic.Height, _
         GraphicsUnit.Pixel, iaPic)

        gfxPic.Dispose()
        Return bmpPic
    End Function

    Private Sub HighlightKey_LocationChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.LocationChanged
        Me.Refresh()
    End Sub

    Private Sub HighlightKey_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.TextChanged
        Me.Refresh()
    End Sub
End Class

我已经创建了一个如上所述的控件，这个控件允许我导入一个带有alpha通道和随机形状的png。然后它可以显示在任何其他控件之上，即文本框，图片框等。并且背景应始终显示其下的内容，而不是仅显示其父控件。

它是否有效，如果它是静态模式，即在表格中静止不动。但是当我试图拖动/移动它时，控件不会正确渲染，也会在其他控件下面。

Answer 1

移动背景时背景不再正确。控件不知道它，你必须通过调用它的Invalidate（）方法告诉它。

它在控件下面浸渍是一个Z阶问题。如果表单包含任何嵌套容器控件（如Panels，UserControls或GroupBoxes），则可能难以修复。你不能把它显示在那些之上。但是只要所有内容都具有父级的形式，然后在控件上调用BringToFront（）将确保它始终位于顶部。

更通用的解决方案是覆盖原始表单并将其TransparencyKey属性设置为BackColor的表单，以使其完全透明。您在该表单上的任何控件将始终位于顶部。我在this thread的代码演示了叠加的想法。

如果您正在创建自己的设计师，那么您将需要阅读this article。