Question

我使用Adorner类为我的控件创建旋转滑块。这是班级的相关部分：

Private initialAngle As Double
Private startVector As Vector
Private currentPoint, centerPoint As Point
Private rotateTransform As RotateTransform

Private RotateThumb As Thumb

Public Sub New(adornedElement As UIElement)
  MyBase.New(adornedElement)
  AddHandler RotateThumb.DragStarted, AddressOf HandleRotateStart
  AddHandler RotateThumb.DragDelta, AddressOf HandleRotate
End Sub

Private Sub HandleRotateStart(sender As Object, e As DragStartedEventArgs)
  Dim AE As FrameworkElement = TryCast(Me.AdornedElement, FrameworkElement)
  centerPoint = New Point(AE.Width / 2, AE.Height / 2)

  Dim startPoint As Point = Mouse.GetPosition(AE.Parent)
  startVector = Point.Subtract(centerPoint, startPoint)

  rotateTransform = TryCast(AE.RenderTransform, RotateTransform)
  If rotateTransform Is Nothing Then
    AE.RenderTransform = New RotateTransform(0, centerPoint.X, centerPoint.Y)
    initialAngle = 0
  Else
    initialAngle = rotateTransform.Angle
  End If
End Sub

Private Sub HandleRotate(sender As Object, e As DragDeltaEventArgs)
  Dim AE As FrameworkElement = TryCast(Me.AdornedElement, FrameworkElement)

  currentPoint = Mouse.GetPosition(AE.Parent)
  Dim deltaVector As Vector = Point.Subtract(centerPoint, currentPoint)

  Dim angle As Double = Vector.AngleBetween(deltaVector, startVector)

  Dim myrotateTransform = TryCast(AE.RenderTransform, RotateTransform)
  myrotateTransform.Angle = initialAngle + Math.Round(angle, 0)
  AE.InvalidateMeasure()
End Sub

Protected Overrides Sub OnRender(drawingContext As DrawingContext)
  MyBase.OnRender(drawingContext)

  If Mouse.LeftButton = MouseButtonState.Pressed Then
    drawingContext.DrawEllipse(New SolidColorBrush(Color.FromArgb(100, 0, 255, 0)), New Pen(Brushes.Green, 1), centerPoint, 10, 10)
    drawingContext.DrawEllipse(New SolidColorBrush(Color.FromArgb(100, 255, 0, 0)), New Pen(Brushes.Red, 1), currentPoint, 7, 7)
  End If
End Sub

虽然这样做（有点）旋转元素，问题是currentPoint似乎不是我的鼠标指针所在的位置（OnRender的红色椭圆不跟随鼠标正确）。我怀疑这可能与RenderTransform有关，我应用于影响DrawingContext的元素。或者它是关于我在这里做的数学？

旋转数学在WPF中无法正常工作

0 个答案: