如何安排在WPF自定義Adorner中的線的拇指

Question

我正在使用WPF繪圖程序中的線的裝飾者。該線是在代碼後面繪製，然後用我的定製裝飾者LineAdorner裝飾。我設法使用Thumb作爲線的起點和終點。我的問題是拇指關於開始和結束點的安排。我認爲問題出在ArrangeOverride的方法中，其中應該用起點和終點排列拇指。我找不到在RectX和Y參數中減去或添加的正確數量。我怎麼能找到這些值總是安排拇指與線的點？ 從我的自定義裝飾器的代碼是這樣的：

 
 

public class LineAdorner : Adorner 
{ 
    private Point start; 
    private Point end; 
    private Thumb startThumb; 
    private Thumb endThumb; 
    private Line selectedLine; 
    private VisualCollection visualChildren; 

    // Constructor 
    public LineAdorner(UIElement adornedElement) : base(adornedElement) 
    { 
     visualChildren = new VisualCollection(this); 

     startThumb = new Thumb { Cursor = Cursors.Hand, Width = 10, Height = 10, Background = Brushes.Green }; 
     endThumb = new Thumb { Cursor = Cursors.Hand, Width = 10, Height = 10, Background = Brushes.BlueViolet }; 

     startThumb.DragDelta += StartDragDelta; 
     endThumb.DragDelta += EndDragDelta; 

     visualChildren.Add(startThumb); 
     visualChildren.Add(endThumb); 

     selectedLine = AdornedElement as Line; 
    } 

    // Event for the Thumb Start Point 
    private void StartDragDelta(object sender, DragDeltaEventArgs e) 
    { 
     Point position = Mouse.GetPosition(this); 

     selectedLine.X1 = position.X; 
     selectedLine.Y1 = position.Y; 
    } 

    // Event for the Thumb End Point 
    private void EndDragDelta(object sender, DragDeltaEventArgs e) 
    { 
     Point position = Mouse.GetPosition(this); 

     selectedLine.X2 = position.X; 
     selectedLine.Y2 = position.Y; 
    } 

    protected override int VisualChildrenCount { get { return visualChildren.Count; } } 
    protected override Visual GetVisualChild(int index) { return visualChildren[index]; } 

    protected override void OnRender(DrawingContext drawingContext) 
    { 
     if (AdornedElement is Line) 
     { 
      selectedLine = AdornedElement as Line; 
      start = new Point(selectedLine.X1, selectedLine.Y1); 
      end = new Point(selectedLine.X2, selectedLine.Y2); 
      } 
    } 

    protected override Size ArrangeOverride(Size finalSize) 
    { 
     var startRect = new Rect(selectedLine.X1, selectedLine.Y1, ActualWidth, ActualHeight); 
     startThumb.Arrange(startRect); 

     var endRect = new Rect(selectedLine.X2, selectedLine.Y2, ActualWidth, ActualHeight); 
     endThumb.Arrange(endRect); 

     return finalSize; 
    } 
    } 

Answer 1

在ArrangeOverride試試這個。你可以擺脫「開始」和「結束」變量，並且你不需要重寫OnRender，因爲如果你告訴它們他們需要的位置，你的拇指就會自己渲染自己。

protected override Size ArrangeOverride(Size finalSize) 
{ 
    selectedLine = AdornedElement as Line; 

    double left = Math.Min(selectedLine.X1, selectedLine.X2); 
    double top = Math.Min(selectedLine.Y1, selectedLine.Y2); 

    var startRect = new Rect(selectedLine.X1 - (startThumb.Width/2), selectedLine.Y1 - (startThumb.Width/2), startThumb.Width, startThumb.Height); 
    startThumb.Arrange(startRect); 

    var endRect = new Rect(selectedLine.X2 - (endThumb.Width/2), selectedLine.Y2 - (endThumb.Height/2), endThumb.Width, endThumb.Height); 
    endThumb.Arrange(endRect); 

    return finalSize; 
} 

您正在拇指上設置顯式大小，因此必須在排列中進行維護。此外，您需要減去拇指的寬度和高度的一半以集中終點。

由於Canvas和Shapes的特性，您需要減去該行的「真實」左值和上值，因爲與Line不同，裝飾者不會從左上角帆布。除了使用Canvasses之外，這不是必需的。