如果我的Canvas元素的DataContext中有以下四个属性
Point Center
double Radius
double StartAngle
double EndAngle
我可以在没有任何额外代码的情况下绘制弧线吗？
答案 0 :(得分：24)
提供自定义组件是最佳解决方案。我在我的代码
中使用它<Controls:Arc Center="{Binding Path=PreviousMousePositionPixels}"
Stroke="White"
StrokeDashArray="4 4"
SnapsToDevicePixels="True"
StartAngle="0"
EndAngle="{Binding Path=DeltaAngle}"
SmallAngle="True"
Radius="40" />
SmallAngle当true呈现点之间的小角度时，无论StartAngle和EndAngle的顺序如何。当SmallAngle为false时，弧线会逆时针呈现。
实施
using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Media;
using System.Windows.Shapes;
public sealed class Arc : Shape
{
public Point Center
{
get => (Point)GetValue(CenterProperty);
set => SetValue(CenterProperty, value);
}
// Using a DependencyProperty as the backing store for Center. This enables animation, styling, binding, etc...
public static readonly DependencyProperty CenterProperty =
DependencyProperty.Register(nameof(Center), typeof(Point), typeof(Arc),
new FrameworkPropertyMetadata(new Point(), FrameworkPropertyMetadataOptions.AffectsRender));
public double StartAngle
{
get => (double)GetValue(StartAngleProperty);
set => SetValue(StartAngleProperty, value);
}
// Using a DependencyProperty as the backing store for StartAngle. This enables animation, styling, binding, etc...
public static readonly DependencyProperty StartAngleProperty =
DependencyProperty.Register(nameof(StartAngle), typeof(double), typeof(Arc),
new FrameworkPropertyMetadata(0.0, FrameworkPropertyMetadataOptions.AffectsRender));
public double EndAngle
{
get => (double)GetValue(EndAngleProperty);
set => SetValue(EndAngleProperty, value);
}
// Using a DependencyProperty as the backing store for EndAngle. This enables animation, styling, binding, etc...
public static readonly DependencyProperty EndAngleProperty =
DependencyProperty.Register(nameof(EndAngle), typeof(double), typeof(Arc),
new FrameworkPropertyMetadata(Math.PI / 2.0, FrameworkPropertyMetadataOptions.AffectsRender));
public double Radius
{
get => (double)GetValue(RadiusProperty);
set => SetValue(RadiusProperty, value);
}
// Using a DependencyProperty as the backing store for Radius. This enables animation, styling, binding, etc...
public static readonly DependencyProperty RadiusProperty =
DependencyProperty.Register(nameof(Radius), typeof(double), typeof(Arc),
new FrameworkPropertyMetadata(10.0, FrameworkPropertyMetadataOptions.AffectsRender));
public bool SmallAngle
{
get => (bool)GetValue(SmallAngleProperty);
set => SetValue(SmallAngleProperty, value);
}
// Using a DependencyProperty as the backing store for SmallAngle. This enables animation, styling, binding, etc...
public static readonly DependencyProperty SmallAngleProperty =
DependencyProperty.Register(nameof(SmallAngle), typeof(bool), typeof(Arc),
new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.AffectsRender));
static Arc() => DefaultStyleKeyProperty.OverrideMetadata(typeof(Arc), new FrameworkPropertyMetadata(typeof(Arc)));
protected override Geometry DefiningGeometry
{
get
{
double a0 = StartAngle < 0 ? StartAngle + 2 * Math.PI : StartAngle;
double a1 = EndAngle < 0 ? EndAngle + 2 * Math.PI : EndAngle;
if (a1 < a0)
a1 += Math.PI * 2;
SweepDirection d = SweepDirection.Counterclockwise;
bool large;
if (SmallAngle)
{
large = false;
d = (a1 - a0) > Math.PI ? SweepDirection.Counterclockwise : SweepDirection.Clockwise;
}
else
large = (Math.Abs(a1 - a0) < Math.PI);
Point p0 = Center + new Vector(Math.Cos(a0), Math.Sin(a0)) * Radius;
Point p1 = Center + new Vector(Math.Cos(a1), Math.Sin(a1)) * Radius;
List<PathSegment> segments = new List<PathSegment>
{
new ArcSegment(p1, new Size(Radius, Radius), 0.0, large, d, true)
};
List<PathFigure> figures = new List<PathFigure>
{
new PathFigure(p0, segments, true)
{
IsClosed = false
}
};
return new PathGeometry(figures, FillRule.EvenOdd, null);
}
}
}
答案 1 :(得分：3)
我可以提供略有不同的解决方案吗？
class ArcII:FrameworkElement
{
/// <summary>
/// Center point of Arc.
/// </summary>
[Category("Arc")]
public Point Center
{
get { return (Point)GetValue(CenterProperty); }
set { SetValue(CenterProperty, value); }
}
// Using a DependencyProperty as the backing store for Center. This enables animation, styling, binding, etc...
public static readonly DependencyProperty CenterProperty =
DependencyProperty.Register("Center", typeof(Point), typeof(ArcII), new FrameworkPropertyMetadata(new Point(0, 0), FrameworkPropertyMetadataOptions.AffectsRender));
/// <summary>
/// Forces the Arc to the center of the Parent container.
/// </summary>
[Category("Arc")]
public bool OverrideCenter
{
get { return (bool)GetValue(OverrideCenterProperty); }
set { SetValue(OverrideCenterProperty, value); }
}
// Using a DependencyProperty as the backing store for OverrideCenter. This enables animation, styling, binding, etc...
public static readonly DependencyProperty OverrideCenterProperty =
DependencyProperty.Register("OverrideCenter", typeof(bool), typeof(ArcII), new FrameworkPropertyMetadata((bool)false, FrameworkPropertyMetadataOptions.AffectsRender));
/// <summary>
/// Start angle of arc, using standard coordinates. (Zero is right, CCW positive direction)
/// </summary>
[Category("Arc")]
public double StartAngle
{
get { return (double)GetValue(StartAngleProperty); }
set { SetValue(StartAngleProperty, value); }
}
// Using a DependencyProperty as the backing store for StartAngle. This enables animation, styling, binding, etc...
public static readonly DependencyProperty StartAngleProperty =
DependencyProperty.Register("StartAngle", typeof(double), typeof(ArcII), new FrameworkPropertyMetadata(0.0, FrameworkPropertyMetadataOptions.AffectsRender));
/// <summary>
/// Length of Arc in degrees.
/// </summary>
[Category("Arc")]
public double SweepAngle
{
get { return (double)GetValue(SweepAngleProperty); }
set { SetValue(SweepAngleProperty, value); }
}
// Using a DependencyProperty as the backing store for SweepAngle. This enables animation, styling, binding, etc...
public static readonly DependencyProperty SweepAngleProperty =
DependencyProperty.Register("SweepAngle", typeof(double), typeof(ArcII), new FrameworkPropertyMetadata((double)180, FrameworkPropertyMetadataOptions.AffectsRender));
/// <summary>
/// Size of Arc.
/// </summary>
[Category("Arc")]
public double Radius
{
get { return (double)GetValue(RadiusProperty); }
set { SetValue(RadiusProperty, value); }
}
// Using a DependencyProperty as the backing store for Radius. This enables animation, styling, binding, etc...
public static readonly DependencyProperty RadiusProperty =
DependencyProperty.Register("Radius", typeof(double), typeof(ArcII), new FrameworkPropertyMetadata(10.0, FrameworkPropertyMetadataOptions.AffectsRender));
[Category("Arc")]
public Brush Stroke
{
get { return (Brush)GetValue(StrokeProperty); }
set { SetValue(StrokeProperty, value); }
}
// Using a DependencyProperty as the backing store for Stroke. This enables animation, styling, binding, etc...
public static readonly DependencyProperty StrokeProperty =
DependencyProperty.Register("Stroke", typeof(Brush), typeof(ArcII), new FrameworkPropertyMetadata((Brush)Brushes.Black,FrameworkPropertyMetadataOptions.AffectsRender));
[Category("Arc")]
public double StrokeThickness
{
get { return (double)GetValue(StrokeThicknessProperty); }
set { SetValue(StrokeThicknessProperty, value); }
}
// Using a DependencyProperty as the backing store for StrokeThickness. This enables animation, styling, binding, etc...
public static readonly DependencyProperty StrokeThicknessProperty =
DependencyProperty.Register("StrokeThickness", typeof(double), typeof(ArcII), new FrameworkPropertyMetadata((double)1,FrameworkPropertyMetadataOptions.AffectsRender));
protected override void OnRender(DrawingContext dc)
{
base.OnRender(dc);
Draw(dc);
}
private void Draw(DrawingContext dc)
{
Point center = new Point();
if (OverrideCenter)
{
Rect rect = new Rect(RenderSize);
center = Polar.CenterPointFromRect(rect);
}
else
{
center = Center;
}
Point startPoint = Polar.PolarToCartesian(StartAngle, Radius, center);
Point endPoint = Polar.PolarToCartesian(StartAngle + SweepAngle, Radius, center);
Size size = new Size(Radius, Radius);
bool isLarge = (StartAngle + SweepAngle) - StartAngle > 180;
List<PathSegment> segments = new List<PathSegment>(1);
segments.Add(new ArcSegment(endPoint, new Size(Radius, Radius), 0.0, isLarge, SweepDirection.Clockwise, true));
List<PathFigure> figures = new List<PathFigure>(1);
PathFigure pf = new PathFigure(startPoint, segments, true);
pf.IsClosed = false;
figures.Add(pf);
Geometry g = new PathGeometry(figures, FillRule.EvenOdd, null);
dc.DrawGeometry(null, new Pen(Stroke,StrokeThickness), g);
}
}
用法：
<!--Centerd on Parent-->
<local:ArcII Center="0,0"
OverrideCenter="True"
StartAngle="150"
SweepAngle="240"
Radius="100"
Stroke="Red"
StrokeThickness="3"
/>
<!--Centerd on Parent-->
<local:ArcII Center="0,0"
OverrideCenter="True"
StartAngle="150"
SweepAngle="240"
Radius="95"
Stroke="Red"
StrokeThickness="3"
/>
<!--Centerd on Parent-->
<local:ArcII Center="0,0"
OverrideCenter="True"
StartAngle="150"
SweepAngle="240"
Radius="90"
Stroke="Red"
StrokeThickness="3"
/>
<!--Centerd on Point-->
<local:ArcII Center="0,150"
OverrideCenter="False"
StartAngle="270"
SweepAngle="180"
Radius="100"
/>
<!--Centerd on Point-->
<local:ArcII Center="525,150"
OverrideCenter="False"
StartAngle="90"
SweepAngle="180"
Radius="100"
/>
注意： A）这不会做360 SweepAngle，因为使用椭圆。 B）OverrideCenter：这将Arc的中心放在其父级的中心。请注意，像Grid这样可以分区的元素仍然有一个中心，可能不是Arc所在的列或行。