拖放后将 PictureBox 捕捉到按钮

Question

我正在制作一款战舰游戏，我正在使用按钮作为网格（玩家面板）。我正在使用一个图片框作为船，我正在努力使图片框捕捉到它与之碰撞的按钮。

我已经完成了拖放和碰撞部分，但我正在努力处理捕捉到按钮的部分。图片框是两个按钮的大小。我试图通过使用 picturebox.left = button.left 将图片框与按钮对齐，但它选择了两个错误的按钮。

Dim Off As Point
Private Sub picDestroyer_MouseDown(sender As Object, e As MouseEventArgs) Handles picDestroyer.MouseDown
    Off.X = MousePosition.X - sender.Left 'Click and Drag ship
    Off.Y = MousePosition.Y - sender.Top
End Sub

Private Sub picDestroyer_MouseMove(sender As Object, e As MouseEventArgs) Handles picDestroyer.MouseMove
    If e.Button = MouseButtons.Left Then
        sender.Left = MousePosition.X - Off.X 'Click and Drag ship
        sender.Top = MousePosition.Y - Off.Y
    End If
End Sub
Private Sub picDestroyer_DoubleClick(sender As Object, e As EventArgs) Handles picDestroyer.DoubleClick
    If picDestroyer.Size = New Size(52, 21) Then 'Rotate Pic if double clicked
        picDestroyer.Size = New Size(21, 52)
    ElseIf picDestroyer.Size = New Size(21, 52) Then
        picDestroyer.Size = New Size(52, 21)
    End If
End Sub
Private Sub picDestroyer_MouseLeave(sender As Object, e As EventArgs) Handles picDestroyer.MouseLeave

    For Each button In Me.Controls
        If picDestroyer.Bounds.IntersectsWith(button.bounds) Then
            button.backcolor = Color.Red
            picDestroyer.BackColor = SystemColors.Control
        End If
        If picDestroyer.Bounds.IntersectsWith(button.bounds) And picDestroyer.Size = New Size(52, 21) Then
            picDestroyer.Top = button.top
        End If
        If picDestroyer.Bounds.IntersectsWith(button.bounds) And picDestroyer.Size = New Size(21, 52) Then
            picDestroyer.Left = button.left
        End If
    Next

Answer 1

要获取您想要对齐的按钮，您可以暂时禁用 PictureBox 并调用 GetChildAtPoint() on the form to get the child control at the location of the PictureBox, specifying GetChildAtPointSkip.Disabled 作为第二个参数，这样搜索就不会包括您禁用的 PictureBox 但所有其他控件 above/below 它。

之后，您只需将 PictureBox 的坐标设置为按钮的坐标即可。

还可以对您的代码进行一些改进：

您可以使用 MouseUp event 而不是 MouseLeave 来在您放下图片框后立即更新它的位置。
在对齐时为图片框设置X-和Y-coordinates（不只是其中一个，Left = X, Top = Y），以便在top-left 按钮的角。
在循环中遍历 Me.Controls.OfType(Of Button)() 而不仅仅是 Me.Controls，因为 OfType(Of TResult) 将获得只有控件某种类型（在本例中为 Buttons）。例如，仅迭代 Me.Controls 将包括 PictureBox 本身，这可能会在将来引起问题（也许这就是您每次将其 BackColor 设置为 Control 的原因？） .

综上所述，这段代码应该可以工作：

If e.Button = Windows.Forms.MouseButtons.Left Then

    picDestroyer.Enabled = False 'Temporarily disable the picture box so that it isn't included in the child search.
    Dim ChildBelowDestroyer As Control = Me.GetChildAtPoint(picDestroyer.Location, GetChildAtPointSkip.Disabled) 'Look for any child control that isn't disabled.
    picDestroyer.Enabled = True 'Re-enable the picture box.

    If ChildBelowDestroyer Is Nothing OrElse _
        ChildBelowDestroyer.GetType() IsNot GetType(Button) Then
        Return 'Do not continue if no child was found below the picture box, or if the child is not a button.
    End If

    picDestroyer.Location = ChildBelowDestroyer.Location 'Snap the picture box to the button (sets the X- and Y-coordinates).

    For Each button In Me.Controls.OfType(Of Button)() 'OfType() to only look for buttons.
        If picDestroyer.Bounds.IntersectsWith(button.Bounds) Then
            button.BackColor = Color.Red
            picDestroyer.BackColor = SystemColors.Control
        End If
    Next

End If

要记住的另一件事是使用 AndAlso instead of And, and OrElse instead of Or in If-statements since AndAlso and OrElse are short-circuited.

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