vb.net 在屏幕或父级上居中表单
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Center form on screen or on parent
提问by Wine Too
Since built in functionality for positioning forms in VB.NET are not always suitable to use I try to make my sub to do that.
由于 VB.NET 中用于定位表单的内置功能并不总是适合使用，因此我尝试让我的子程序做到这一点。
But I missed something...
但我错过了一些东西......
Public Sub form_center(ByVal frm As Form, Optional ByVal parent As Form = Nothing)
Dim x As Integer
Dim y As Integer
Dim r As Rectangle
If Not parent Is Nothing Then
r = parent.ClientRectangle
x = r.Width - frm.Width + parent.Left
y = r.Height - frm.Height + parent.Top
Else
r = Screen.PrimaryScreen.WorkingArea
x = r.Width - frm.Width
y = r.Height - frm.Height
End If
x = CInt(x / 2)
y = CInt(y / 2)
frm.StartPosition = FormStartPosition.Manual
frm.Location = New Point(x, y)
End Sub
How to get this sub to place form correctly in the middle of the screen or other form if is defined?
如果已定义，如何让这个 sub 将表单正确地放置在屏幕或其他表单的中间？
回答by mike100111
I know this is an old post and this doesn't directly answer the question, but for anyone else who stumbles upon this thread, centering a form can be done simply without requiring you to write your own procedure.
我知道这是一篇旧帖子，这并没有直接回答问题，但是对于偶然发现此线程的任何其他人，可以简单地将表单居中，而无需您编写自己的程序。
The System.Windows.Forms.Form.CenterToScreen()and System.Windows.Forms.Form.CenterToParent()allow you to center the a form in reference to the screen or in reference to the parent form depending on which one you need.
在 System.Windows.Forms.Form.CenterToScreen()和System.Windows.Forms.Form.CenterToParent()允许您居中表格中提到的屏幕或引用具体取决于您需要的父窗体。
One thing to note is that these procedures MUSTbe called before the form is loaded. It is best to call them in the form_load event handler.
需要注意的一件事是，必须在加载表单之前调用这些过程。最好在 form_load 事件处理程序中调用它们。
EXAMPLE CODE:
示例代码：
Private Sub Settings_Load(sender As Object, e As EventArgs) Handles Me.Load
Me.CenterToScreen()
'or you can use
Me.CenterToParent()
End Sub
回答by Hans Passant
The code is just wrong. It is also essential that this code runs late enough, the constructor is too early. Be sure to call it from the Load event, at that time the form is properly auto-scaled and adjusted for the user's preferences, the StartPosition property no longer matters then. Fix:
只是代码错了。这段代码运行得足够晚也很重要，构造函数太早了。一定要从 Load 事件中调用它，那时表单会根据用户的偏好正确自动缩放和调整，然后 StartPosition 属性不再重要。使固定：
Public Shared Sub CenterForm(ByVal frm As Form, Optional ByVal parent As Form = Nothing)
'' Note: call this from frm's Load event!
Dim r As Rectangle
If parent IsNot Nothing Then
r = parent.RectangleToScreen(parent.ClientRectangle)
Else
r = Screen.FromPoint(frm.Location).WorkingArea
End If
Dim x = r.Left + (r.Width - frm.Width) \ 2
Dim y = r.Top + (r.Height - frm.Height) \ 2
frm.Location = New Point(x, y)
End Sub
Incidentally, one of the very few reasons to actually implement the Load event handler.
顺便说一下，这是实际实现 Load 事件处理程序的极少数原因之一。
回答by user3012629
This might also be of use:
这也可能有用：
myForm.StartPosition = FormStartPosition.CenterParent
myForm.ShowDialog()
You can also use FormStartPosition.CenterScreen
您还可以使用 FormStartPosition.CenterScreen
回答by Marco Sanchez
I had the problem with StartPosition = CenterParentnot working. I solved it calling the form with .ShowDialog()instead of .Show():
我遇到了StartPosition = CenterParent无法工作的问题。我解决了它调用表单.ShowDialog()而不是.Show()：
' first you should set your form's Start Position as Center Parent
Private Sub button_Click(sender As Object, e As EventArgs) Handles button.Click
MyForm.ShowDialog()
End Sub
