How to flip a User Control added in a picturebox by 180 degrees?

问题

I'm adding a control to a picturebox. This control is a component, precisely it's a toggle switch posted here. I'd like this control to be vertical and not horizontal .

So, since objects can't be rotated or flipped, I found a way to flip the picturebox image with:

PictureBox1.Image.RotateFlip(RotateFlipType.Rotate180FlipNone)
    PictureBox1.Refresh()

The error I'm getting at RunTime is:

System.Windows.Forms.PictureBox.Image.get returned Nothing

Endeed the control is not an image so is there a way to flip the control inside of the picturebox by 180 degrees? Also, You think there is a way to know when the value of the toggle switch is on or off? Thanks

回答1:

As already mentioned above, extend the control to have it drawn either horizontally or vertically.

Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

Public Class ToggleSwitch
    Inherits CheckBox

    Public Sub New()
        MyBase.New

        SetStyle(ControlStyles.AllPaintingInWmPaint Or
                 ControlStyles.UserPaint, True)
        UpdateStyles()
        Padding = New Padding(6)
    End Sub

    Private _orientation As Orientation = Orientation.Horizontal
    Public Property Orientation As Orientation
        Get
            Return _orientation
        End Get
        Set(value As Orientation)
            _orientation = value

            Dim max = Math.Max(Width, Height)
            Dim min = Math.Min(Width, Height)

            If value = Orientation.Vertical Then
                Size = New Size(min, max)
            Else
                Size = New Size(max, min)
            End If
        End Set
    End Property

    'Fix by: @41686d6564
    <Browsable(False),
    Bindable(False),
    DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
    EditorBrowsable(EditorBrowsableState.Never)>
    Public Overrides Property AutoSize As Boolean
        Get
            Return False
        End Get
        Set(value As Boolean)
        End Set
    End Property

    Protected Overrides Sub OnPaint(e As PaintEventArgs)
        Dim g = e.Graphics

        g.Clear(BackColor)
        g.SmoothingMode = SmoothingMode.AntiAlias
        g.PixelOffsetMode = PixelOffsetMode.Half

        Dim p = Padding.All
        Dim r = 0
        Dim rec As Rectangle

        Using gp = New GraphicsPath
            If _orientation = Orientation.Vertical Then
                r = Width - 2 * p
                gp.AddArc(p, p, r, r, -180, 180)
                gp.AddArc(p, Height - r - p, r, r, 0, 180)
                r = Width - 1
                rec = New Rectangle(0, If(Checked, Height - r - 1, 0), r, r)
                'Or
                'rec = New Rectangle(0, If(Checked, 0, Height - r - 1), r, r)
                'To get the ON on top.
            Else
                r = Height - 2 * p
                gp.AddArc(p, p, r, r, 90, 180)
                gp.AddArc(Width - r - p, p, r, r, -90, 180)
                r = Height - 1
                rec = New Rectangle(If(Checked, Width - r - 1, 0), 0, r, r)
            End If

            gp.CloseFigure()

            g.FillPath(If(Checked, Brushes.DarkGray, Brushes.LightGray), gp)
            g.FillEllipse(If(Checked, Brushes.Green, Brushes.WhiteSmoke), rec)
        End Using
    End Sub

End Class

As for the second part of your question, please read CheckBox.Checked property and CheckBox.CheckedChanged event.

Impelemntation example:

Private Sub ToggleSwitch1_CheckedChanged(sender As Object, e As EventArgs) Handles ToggleSwitch1.CheckedChanged
    If ToggleSwitch1.Checked Then
        'ToDo with ON state...
    Else
        'ToDo with OFF state..
    End If
End Sub

来源：https://stackoverflow.com/questions/64236248/how-to-flip-a-user-control-added-in-a-picturebox-by-180-degrees