允许最终用户移动控件

Question

我找到了一个很好的示例 这里，但我有一些问题。 1. 由于控件太大，没有将控件放置到鼠标离开的正确位置。

2. 它可以被推出屏幕。我希望它应该保持在屏幕边界内。

这是我的代码：

   Public Sub Form1_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyControl.MouseMove
    If Not _capturingMoves Then
        Return
    End If
    X = e.X
    Y = e.Y
End Sub

Public Sub Form1_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs) Handles MyControl.MouseUp
    If _capturingMoves Then
        ' Do any final placement
        MyControl.Location = New Point(X, Y)
        _capturingMoves = False
    End If
End Sub

Answer 1

我写了这样的东西来在网页上拖动div...

一般方法是保存 mousedown 上的坐标，获取 mouseup 上的坐标，然后根据差异移动对象的位置。

下面是一些示例代码：

我创建了一个 DragInfo 类，用于保留初始鼠标坐标和初始位置。然后，我在 mousedown 事件上将其中一个存储在控件的 Tag 中：

Public Class DragInfo
    Public Property InitialMouseCoords As Point
    Public Property InitialLocation As Point

    Public Sub New(ByVal MouseCoords As Point, ByVal Location As Point)
        InitialMouseCoords = MouseCoords
        InitialLocation = Location
    End Sub

    Public Function NewLocation(ByVal MouseCoords As Point) As Point
        Dim loc As New Point(InitialLocation.X + (MouseCoords.X - InitialMouseCoords.X), InitialLocation.Y + (MouseCoords.Y - InitialMouseCoords.Y))
        Return loc
    End Function
End Class

我的测试控件只是我从工具箱中放入的一个面板。我猜它可能是任何东西。以下是面板 (Panel1) 的 mousedown、mousemove 和 mouseup 事件处理程序：

Private Sub Panel1_MouseDown(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseDown
    Panel1.Tag = New DragInfo(Form.MousePosition, Panel1.Location)
End Sub

Private Sub Panel1_MouseMove(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseMove
    If Panel1.Tag IsNot Nothing Then
        Dim info As DragInfo = CType(Panel1.Tag, DragInfo)
        Dim newLoc As Point = info.NewLocation(Form.MousePosition)
        If Me.ClientRectangle.Contains(New Rectangle(newLoc, Panel1.Size)) Then Panel1.Location = newLoc
    End If
End Sub

Private Sub Panel1_MouseUp(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseUp
    Panel1.Tag = Nothing
End Sub

就是这样！那行得通。请注意，mousemove 方法检查控件是否位于窗体的 clientrectangle 内。

或者，一种更通用的方法：

Private Sub MakeDraggable(ByVal Control As Control)
    AddHandler Control.MouseDown, Sub(sender As Object, e As MouseEventArgs) StartDrag(Control)
    AddHandler Control.MouseMove, Sub(sender As Object, e As MouseEventArgs) Drag(Control)
    AddHandler Control.MouseUp, Sub(sender As Object, e As MouseEventArgs) StopDrag(Control)
End Sub
Private Sub StartDrag(ByVal Control As Control)
    Control.Tag = New DragInfo(Form.MousePosition, Control.Location)
End Sub
Private Sub Drag(ByVal Control As Control)
    If Control.Tag IsNot Nothing AndAlso TypeOf Control.Tag Is DragInfo Then
        Dim info As DragInfo = CType(Control.Tag, DragInfo)
        Dim newLoc As Point = info.NewLocation(Form.MousePosition)
        If Me.ClientRectangle.Contains(New Rectangle(newLoc, Control.Size)) Then Control.Location = newLoc
    End If
End Sub
Private Sub StopDrag(ByVal Control As Control)
    Control.Tag = Nothing
End Sub

现在您可以使用 MakeDraggable(Panel1) 或任何其他控件来使其可拖动！

编辑：两个示例现在都可以防止控件被拖出边界。