Question

我遇到了一些问题。我在我的应用程序中有mdi表单我有第一个表单，我使用按钮单击。我想如果点击这个按钮我的第二个表格（如果它打开）提高它的方法。请注意，第二种形式不是第一种形式的孩子（然后我将传递给它的构造函数），但在这里它们是分开的。怎么做？到目前为止我尝试的是：

第一种形式：

Public Class FrmFirst

    Public Event Start(ByVal sender As Object, ByVal e As System.EventArgs)

    Public Sub btnAdd_Click(sender As System.Object, e As System.EventArgs) Handles btnAdd.Click
        Some code...
            RaiseEvent Start(Me, e)  'raise event
    End Sub

第二种形式：

Public Class FrmSecond

'Static
    Public WithEvents MySender As FrmFirst

'method which should be executed
 Public Sub alejaja(sender As System.Object, e As System.EventArgs) Handles MySender.Start
        ReloadGrid()
End Sub

更新

可以从toolsstrip标签打开FrmFirst：

  Private Sub ToolStripLabelFrmFirst _Click(sender As System.Object, e As System.EventArgs) Handles ToolStripLabelFrmFirst.Click
        Dim First As New FrmFirst 
            First.MdiParent = Me
            First.Show()
    End Sub

FrmSecond可以从其他toolsstriplabel中以相同的方式打开：

   Private Sub ToolStripLabelFrmSecond_Click(sender As System.Object, e
As System.EventArgs) Handles ToolStripLabelFrmSecond.Click
         Dim Second As New FrmSecond()
             Second.MdiParent = Me
             Second.Show()
     End Sub

Answer 1

您的 MySender 变量始终为Nothing，您永远不会对其进行初始化。所以它也不会发现任何事件。你在这里违反了设计模式，一个表格类别不应该对另一个表格类别有任何了解。除了您的MDI父类之外，它必须知道所有这些，因为它创建了它们的实例。

通过将ReloadGrid（）方法设为public来开始修复此问题。在您的MDI父表单中，编写用于跟踪FrmFirst生命周期的代码，以便您可以在必要时正确更新它。像这样：

Private FrmFirst First;

Private Sub ToolStripLabelFrmFirst _Click(sender As System.Object, e As System.EventArgs) Handles ToolStripLabelFrmFirst.Click
    If First IsNot Nothing Then
        First.WindowState = FormWindowState.Normal
    Else
        First = New FrmFirst 
        First.MdiParent = Me
        AddHandler First.FormClosed, Sub(s, ea)
                                         First = Nothing
                                     End Sub
    End Sub
    First.Show()
End Sub

现在，您可以使用第二种形式触发的事件更新网格：

Private Sub ToolStripLabelFrmSecond_Click(sender As System.Object, e As System.EventArgs) Handles ToolStripLabelFrmSecond.Click
    Dim Second As New FrmSecond()
    Second.MdiParent = Me
    AddHandler Second.Start, Sub(s, ea)
                                 If First IsNot Nothing Then First.ReloadGrid()
                             End Sub
    Second.Show()
End Sub

未经测试，应该关闭。

Answer 2

您应该为从FrmFirst实例接收事件的事件创建一个“hub”，并将它们分派到FrmSecond个实例。我们可以使用主窗体，因为它在两个类中都有引用。

在您的主表单中，为您创建的每个Start实例添加Start事件并处理FrmFirst事件：

Public Event Start(ByVal sender As Object, ByVal e As System.EventArgs)

' Start events raised from every FrmFirst instance will invoke this method
Private Sub First_Start(ByVal sender As Object, ByVal e As System.EventArgs)
    ' And this will invoke every FrmSecond instance's event handlers
    RaiseEvent Start(sender, e)
End Sub

Private Sub ToolStripLabelFrmFirst _Click(sender As System.Object, e As System.EventArgs) Handles ToolStripLabelFrmFirst.Click
    Dim First As New FrmFirst 
    First.MdiParent = Me
    AddHandler First.Start , AddressOf First_Start
    First.Show()
End Sub

然后在创建FrmSecond实例时为此新事件添加处理程序：

Private Sub ToolStripLabelFrmSecond_Click(sender As System.Object, _
             e As System.EventArgs) Handles ToolStripLabelFrmSecond.Click
     Dim Second As New FrmSecond()
     Second.MdiParent = Me
     AddHandler Me.Start, AddressOf Second.alejaja ' This will make the object receive Start events from FrmMain

     Second.Show()
End Sub

当然，您应该在Forms的Closed事件上使用RemoveHandler来防止内存泄漏。这是FrmSecond内部的方式：

Private Sub Form_Closed(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles MyBase.Closed

    ' Replace Form1 with your Mdi parent form's class name
    RemoveHandler CType(Me.MdiParent, Form1).Start, AddressOf Me.alejaja 
End Sub

其他表单操作后调用表单方法

2 个答案: