Question

我有一个带有picturecontrol的表单（默认为black bg），下面有一个flowlayoutpanel。在表单的加载上，它循环浏览图像文件夹，并在flowlayoutpanel内创建缩略图（picturecontrol）。我想要做的是动态添加一个click事件，让用户使用其中一个缩略图更改主picturecontrol图像。

Private Sub TabImageLoad()
    Dim apppath As String = Application.StartupPath()
    Dim strFileSize As String = ""
    Dim di As New IO.DirectoryInfo(apppath + "\images")
    Dim aryFi As IO.FileInfo() = di.GetFiles("*.*")
    Dim fi As IO.FileInfo

    For Each fi In aryFi
        If fi.Extension = ".jpg" Or fi.Extension = ".jpeg" Or fi.Extension = ".gif" Or fi.Extension = ".bmp" Then
            Dim temp As New PictureBox
            temp.Image = Image.FromFile(di.ToString + "\" + fi.ToString)
            temp.Width = 100
            temp.Height = 75
            temp.Name = fi.ToString
            temp.Visible = True
            temp.SizeMode = PictureBoxSizeMode.StretchImage
            AddHandler temp.Click, AddressOf Me.temp_click
            FlowLayoutPanel1.Controls.Add(temp)
        End If
    Next
End Sub
Private Sub temp_click(ByVal sender As System.Object, ByVal e As System.EventArgs)
    PictureBox1.Image = temp.Image
End Sub

这是我获取图像的子代码（注意addhandler尝试）和链接到addhandler的子代码。你可能已经猜到了addhandler不能正常工作，因为temp_click子中没有声明“temp”。

有什么建议吗？

Answer 1

sender参数始终是触发事件的控件，在本例中为PictureBox：

Private Sub temp_click(ByVal sender As System.Object, ByVal e As System.EventArgs)
    Dim pb As PictureBox = DirectCast(sender, PictureBox)
    PictureBox1.Image = pb.Image
End Sub

Answer 2

我建议您使用：

Private Sub temp_click(ByVal sender As System.Object, ByVal e As System.EventArgs)
Dim pbDynamic as PictureBox = trycast(sender,Picturebox)

然后用

验证

if pbDynamic IsNot Nothing Then
    PictureBox1.Image = pbDynamic.image
end if

这样可以避免运行时错误和空指针异常

如何从动态控件中获取值？

2 个答案: