Private Sub Form_Load()
    Me.Move 0, 0, Screen.Width, Screen.Height
    'Me.Move (Screen.Width - Me.Width) / 2, (Screen.Height - Me.Height) / 2 设置窗体居中
End Sub

Dim SW As Long, SH As Long
Private Sub Form_Load()
   SW = Screen.Width
   SH = Screen.Height
   Me.Move 0, 0, SW, SH
   Timer1.Interval = 500
   Timer1.Enabled = True
End Sub

Private Sub Timer1_Timer()
   If SW <> Screen.Width And SH <> Screen.Height Then
      SW = Screen.Width
      SH = Screen.Height
      Me.Move 0, 0, SW, SH
   End If
End Sub

Option Explicit
Private Declare Function LockWindowUpdate Lib "user32" (ByVal hwndLock As Long) As Long

' if True, also fonts are resized
'是否缩放字体
Public ResizeFont As Boolean
' if True, form's height/width ratio is preserved
'是否保持比例
Public KeepRatio As Boolean

Private Type TcontrolInfo
    ctrl        As Control
    Left        As Single
    Top         As Single
    Width       As Single
    Height      As Single
    FontSize    As Single
End Type

' this array holds the original position
' and size of all controls on parent form
'保存父窗体内所有控件的初始位置与大小
Dim Controls() As TcontrolInfo

' a reference to the parent form
'父窗体事件
Private WithEvents ParentForm As Form

' parent form's size at load time
'载入时父窗体的大小
Private ParentWidth As Single
Private ParentHeight As Single

' ratio of original height/width
'初始高宽比例
Private HeightWidthRatio As Single

Private Sub ParentForm_Load()
    ' the ParentWidth variable works as a flag
    ParentWidth = 0
    ' save original ratio
    '保存初始比例
    HeightWidthRatio = ParentForm.Height / ParentForm.Width
End Sub

Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
    ResizeFont = PropBag.ReadProperty("ResizeFont", False)
    KeepRatio = PropBag.ReadProperty("KeepRatio", False)
    If Ambient.UserMode = False Then Exit Sub
    ' store a reference to the parent form and
    ' start receiving events
    Set ParentForm = Parent
End Sub

Private Sub UserControl_WriteProperties(PropBag As PropertyBag)
    PropBag.WriteProperty "ResizeFont", ResizeFont, False
    PropBag.WriteProperty "KeepRatio", KeepRatio, False
End Sub

Private Sub UserControl_Resize()
    ' refuse to resize
    '限制大小
    Size 420, 420
End Sub
' trap the parent form's Resize event
' this include the very first resize event
' that occurs soon after form's load
Private Sub ParentForm_Resize()
    'MsgBox "A"
    LockWindowUpdate ParentForm.hwnd
    If ParentWidth = 0 Then
        Rebuild
    Else
        Refresh
    End If
    LockWindowUpdate 0
    'MsgBox "B"
End Sub

' save size and position of all controls on parent form
' you should manually invoke this method each time you
' add a new control to the form
' (through Load method of a control array)
'
Sub Rebuild()
' rebuild the internal table
    Dim I As Integer, ctrl As Control
    ' this is necessary for controls that don't support
    ' all properties (e.g. Timer controls)
    On Error Resume Next
    If Ambient.UserMode = False Then Exit Sub
    ' save a reference to the parent form
    ' and its initial size
    Set ParentForm = UserControl.Parent
    ParentWidth = ParentForm.ScaleWidth
    ParentHeight = ParentForm.ScaleHeight
    ' read the position of all controls on the parent form
    ReDim Controls(ParentForm.Controls.count - 1) As TcontrolInfo
    For I = 0 To ParentForm.Controls.count
        With Controls(I)
            Set .ctrl = ParentForm.Controls(I)
            .Left = ParentForm.Controls(I).Left
            .Top = ParentForm.Controls(I).Top
            .Width = ParentForm.Controls(I).Width
            .Height = ParentForm.Controls(I).Height
            .FontSize = ctrl.Font.Size
        End With
    Next
End Sub

' update size and position of controls on parent form
'更新父窗体内控件的大小与位置
Sub Refresh()
    Dim I As Integer, ctrl As Control
    Dim widthFactor As Single, heightFactor As Single
    Dim minFactor As Single '比例因子
    ' inhibits recursive calls if KeepRatio = True
    Static executing As Boolean
    If executing Then Exit Sub
    '如果不是运行时,则退出
    If Ambient.UserMode = False Then Exit Sub
    If KeepRatio Then
       executing = True
       ' we must keep original ratio
       If ParentForm.WindowState <> 2 And ParentForm.WindowState <> 1 Then ParentForm.Height = HeightWidthRatio * ParentForm.Width
       executing = False
    End If
    ' this is necessary for controls that don't support
    ' all properties (e.g. Timer controls)
    '错误处理,不能调整所有控件的大小,比如 Timer 控件
    On Error Resume Next
    widthFactor = ParentForm.ScaleWidth / ParentWidth
    heightFactor = ParentForm.ScaleHeight / ParentHeight
    ' take the lesser of the two
    If widthFactor < heightFactor Then
       minFactor = widthFactor
    Else
       minFactor = heightFactor
    End If
    ' this is a regular resize
    For I = 0 To UBound(Controls)
       With Controls(I)
        ' the change of font must occur *before* the
        ' resizing to account for companion scrollbar
        ' of listbox and other similar controls
        If ResizeFont Then
            .ctrl.Font.Size = .FontSize * minFactor
        End If
        ' move and resize the controls - we can't use a
        ' Move method because some controls do not
        ' support the change of all the four properties
        ' (eg. Height with comboboxes)
            '.ctrl.Left = .Left * widthFactor
            '.ctrl.Top = .Top * heightFactor
            '.ctrl.Width = .Width * widthFactor
            '.ctrl.Height = .Height * heightFactor
            If InStr(UCase(.ctrl.Name), UCase("combo")) <> 0 Then
                .ctrl.Left = .Left * widthFactor
                .ctrl.Top = .Top * heightFactor
            Else
                .ctrl.Move .Left * widthFactor, .Top * heightFactor, .Width * widthFactor, .Height * heightFactor
            End If
       End With
    Next
    
End Sub