您需要将当前鼠标位置 m2 与缓存鼠标位置 m1 之间的差异添加到 缓存控件位置 c1 给你当前的控制位置c2。
c2 = (c1 + (m2 - m1))
类似这样的：
sender.Location = New Point(
(cachedControlLocation.X + (e.X - startX)),
(cachedControlLocation.Y + (e.Y - startY))
)
这是一个示例表单，向您展示它是如何工作的：
Public Class Form1
Public Sub New()
Me.InitializeComponent()
Me.ClientSize = New Size(800, 600)
Me.panel1 = New Panel() With {.Bounds = New Rectangle(10, 10, 300, 300), .BackColor = Color.Red}
Me.panel2 = New Panel() With {.Bounds = New Rectangle(10, 10, 200, 200), .BackColor = Color.Green}
Me.panel3 = New Panel() With {.Bounds = New Rectangle(10, 10, 100, 100), .BackColor = Color.Blue}
Me.panel2.Controls.Add(Me.panel3)
Me.panel1.Controls.Add(Me.panel2)
Me.Controls.Add(Me.panel1)
End Sub
Private Sub HandleDraggableControlMouseDown(sender As Object, e As MouseEventArgs) Handles panel1.MouseDown, panel2.MouseDown, panel3.MouseDown
Dim target As Control = TryCast(sender, Control)
If (Not target Is Nothing) Then
Dim pt As Point = Me.PointToClient(target.PointToScreen(Point.Empty))
target.Parent = Me
target.BringToFront()
target.Location = pt
Me.isMouseDown = True
Me.cachedControlPos = pt
Me.cachedMousePos = Control.MousePosition
End If
End Sub
Private Sub HandleDraggableControlMouseMove(sender As Object, e As MouseEventArgs) Handles panel1.MouseMove, panel2.MouseMove, panel3.MouseMove
If (Me.isMouseDown) Then
Dim target As Control = TryCast(sender, Control)
If (Not target Is Nothing) Then
Dim x As Integer = (Me.cachedControlPos.X + (Control.MousePosition.X - Me.cachedMousePos.X))
Dim y As Integer = (Me.cachedControlPos.Y + (Control.MousePosition.Y - Me.cachedMousePos.Y))
target.Location = New Point(x, y)
'c2 = (c1 + (m2 - m1))
End If
End If
End Sub
Private Sub HandleDraggableControlMouseUp(sender As Object, e As MouseEventArgs) Handles panel1.MouseUp, panel2.MouseUp, panel3.MouseUp
Me.cachedControlPos = Point.Empty
Me.cachedMousePos = Point.Empty
Me.isMouseDown = False
End Sub
Private cachedMousePos As Point
Private cachedControlPos As Point
Private isMouseDown As Boolean
Private WithEvents panel1 As Panel
Private WithEvents panel2 As Panel
Private WithEvents panel3 As Panel
End Class
更新 1
在更改父级并将其移到前面后设置新位置很重要。
target.Parent = Me
target.BringToFront()
target.Location = pt '<---
更新 2
所以我已将其范围缩小到导致此问题的原因，结果是Selectable control style。您可以通过子类化按钮类并删除构造函数中的样式来验证这一点。
Public Class UIButton
Inherits Button
Public Sub New()
MyBase.SetStyle(ControlStyles.Selectable, False)
End Sub
End Class
那么我们该如何解决这个问题呢？好吧，AFAIK 没有简单的解决方案。可以预料，可选择的控件将以不同于那些不能的方式处理鼠标消息的方式。我能想到的唯一方法（它可能是一种肮脏的方法）是将控件子类化并拦截鼠标消息。以下代码不是最终解决方案，因此请谨慎使用。
Public Class UIButton
Inherits Button
Protected Overrides Sub WndProc(ByRef m As Message)
Select Case m.Msg
Case WM.LBUTTONDOWN
Dim dw As New DWORD With {.value = m.LParam}
Dim vk As Integer = m.WParam.ToInt32()
MyBase.OnMouseDown(New MouseEventArgs(Windows.Forms.MouseButtons.Left, 0, dw.loword, dw.hiword, 0))
Debug.WriteLine("X={0}, Y={1}", dw.loword, dw.hiword)
Exit Select
Case WM.MOVE
Dim dw As New DWORD With {.value = m.LParam}
Dim vk As Integer = m.WParam.ToInt32()
If (vk = Keys.LButton) Then
MyBase.OnMouseMove(New MouseEventArgs(Windows.Forms.MouseButtons.Left, 0, dw.loword, dw.hiword, 0))
Debug.WriteLine("X={0}, Y={1}", dw.loword, dw.hiword)
End If
Exit Select
Case WM.LBUTTONUP
Dim dw As New DWORD With {.value = m.LParam}
Dim vk As Integer = m.WParam.ToInt32()
MyBase.OnMouseUp(New MouseEventArgs(Windows.Forms.MouseButtons.Left, 0, dw.loword, dw.hiword, 0))
Debug.WriteLine("X={0}, Y={1}", dw.loword, dw.hiword)
Exit Select
End Select
MyBase.WndProc(m)
End Sub
Private Enum WM As Integer
MOVE = &H200
LBUTTONDOWN = &H201
LBUTTONUP = &H202
End Enum
<StructLayout(LayoutKind.Explicit)> _
Private Structure DWORD
<FieldOffset(0)> Public value As Integer
<FieldOffset(0)> Public loword As Short
<FieldOffset(2)> Public hiword As Short
End Structure
End Class