在DrawingVisual上绘制圆形的进度条，类似于IOS系统风格。

1.说明：在WPF中，文件下载时需要显示下载进度，由于系统自带的条型进度条比较占用空间，改用圆形的进度条,需要在DrawingVisual上呈现。

运行的效果如图：

               private Point GetPointOnCir(Point CenterPoint, double r, double angel){Point p = new Point();p.X = Math.Sin(angel * Math.PI / 180) * r + CenterPoint.X;p.Y = CenterPoint.Y - Math.Cos(angel * Math.PI / 180) * r;return p;}private Geometry drawingArc(Point bigCirclefirstPoint, Point bigCirclesecondPoint, Point smallCirclefirstPoint, Point smallCirclesecondPoint, double bigCircleRadius, double smallCircleRadius,bool  isLargeArc){PathFigure pathFigure = new PathFigure { IsClosed = true };pathFigure.StartPoint = bigCirclefirstPoint;pathFigure.Segments.Add(new ArcSegment{Point = bigCirclesecondPoint,IsLargeArc = isLargeArc,Size = new Size(bigCircleRadius, bigCircleRadius),SweepDirection = SweepDirection.Clockwise});pathFigure.Segments.Add(new LineSegment { Point = smallCirclesecondPoint });pathFigure.Segments.Add(new ArcSegment{Point = smallCirclefirstPoint,IsLargeArc = isLargeArc,Size = new Size(smallCircleRadius, smallCircleRadius),SweepDirection = SweepDirection.Counterclockwise});PathGeometry pathGeometry = new PathGeometry();pathGeometry.Figures.Add(pathFigure);return pathGeometry;}//根据已保存的大小和文件总大小来计算下载进度百分比private Geometry GetGeometry(){bool isLargeArc =false;double percent = double.Parse(Convert.ToString(savedSize)) / double.Parse(Convert.ToString(fileSize));PercentString = string.Format("{0}%",Math.Round(percent*100,0));double angel = percent * 360D;if(angel>180)isLargeArc=true;//double angel = 45;double bigR = 16;double smallR = 13;Point centerPoint = vl.StartPoint;//new Point(100, 300);Point firstpoint = GetPointOnCir(centerPoint, bigR, 0);Point secondpoint = GetPointOnCir(centerPoint, bigR, angel);Point thirdpoint = GetPointOnCir(centerPoint, smallR, 0);Point fourpoint = GetPointOnCir(centerPoint, smallR, angel);return drawingArc(firstp, secondpoint, thirdpoint, fourpoint, bigR, smallR, isLargeArc);}

 

画圆形的进度条，实际上是动态画两个同心圆，根据文件保存的百分比来计算画弧形的角度的大小，需要7个参数：大圆的半径bigR 、小圆的半径smallR 、同心圆的圆心centerPoint 、大圆的起始点firstpoint 、大圆的结束点secondpoint 、小圆的起始点thirdpoint、小圆的结束点fourpoint

 

 

最后需要使用DrawingContext把圆给画出来：

                public Visual drawShape(){DrawingVisual drawingWordsVisual = new DrawingVisual();DrawingContext drawingContext = drawingWordsVisual.RenderOpen();try{if (savedSize != fileSize){

                                        drawingContext.DrawEllipse(null, new Pen(Brushes.Gray, 3), vl.StartPoint, 13, 13);drawingContext.DrawGeometry(vs.VisualBackgroundBrush, vs.VisualFramePen, GetGeometry());FormattedText formatWords = new FormattedText(PercentString, System.Globalization.CultureInfo.CurrentCulture, FlowDirection.LeftToRight, new Typeface(vs.WordsFont.Name), vs.WordsFont.Size, currentStyle.VisualBackgroundBrush);formatWords.SetFontWeight(FontWeights.Bold);Point startPoint = new Point(vl.StartPoint.X - formatWords.Width / 2, vl.StartPoint.Y - formatWords.Height / 2);drawingContext.DrawText(formatWords, startPoint);}else{drawingContext.DrawEllipse(null, new Pen(Brushes.Green, 3), vl.StartPoint, 16, 16);FormattedText formatWords = new FormattedText("Open", System.Globalization.CultureInfo.CurrentCulture, FlowDirection.LeftToRight, new Typeface(vs.WordsFont.Name), vs.WordsFont.Size, Brushes.Red);formatWords.SetFontWeight(FontWeights.Bold);Point startPoint = new Point(vl.StartPoint.X - formatWords.Width / 2, vl.StartPoint.Y - formatWords.Height / 2);drawingContext.DrawText(formatWords, startPoint);}}catch (Exception ex){new SaveExceptionInfo().SaveLogAsTXTInfoex(ex.Message);}finally{drawingContext.Close();}return drawingWordsVisual;}