vb.net 教程 5-12 绘图实例之统计图 3 饼图

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继续上一期《绘图实例之统计图2》,继续讲解如何绘制饼图:

当按下“饼图”按钮时,调用三个函数,分别是绘制饼图、显示到窗口,由于不需要坐标轴,所以这里不再绘制坐标轴:

    Private Sub btnPie_Click(sender As Object, e As EventArgs) Handles btnPie.Click        Call DrawPie()        Call DrawToForm()    End Sub

DrawToForm()在之前已经介绍,以下是DrawPie的代码:

    '绘制饼图    Private Sub DrawPie()        '标注每个季度        Dim seasonValue(3) As Integer        seasonValue(0) = nudSeason1.Value        seasonValue(1) = nudSeason2.Value        seasonValue(2) = nudSeason3.Value        seasonValue(3) = nudSeason4.Value        Dim seasonName() As String = {"一季度", "二季度", "三季度", "四季度"}        '我们要获得4个季度总的盈利        Dim seasonSum As Integer = 0        For i As Integer = 0 To 3            seasonSum += seasonValue(i)        Next        '根据总赢利情况,来获得每个季度在饼图中所占的份额(角度)        '为了简化起见,这里直接取整数        Dim seasonAngle(4) As Integer        seasonAngle(0) = 0        seasonAngle(1) = seasonValue(0) * 360 \ seasonSum        seasonAngle(2) = seasonValue(1) * 360 \ seasonSum + seasonAngle(1)        seasonAngle(3) = seasonValue(2) * 360 \ seasonSum + seasonAngle(2)        seasonAngle(4) = 360        '分别用4种颜色表示不同季度的盈利--http://blog.csdn.net/uruseibest        Dim seasonColor() As Color = {Color.Red, Color.Blue, Color.Green, Color.GreenYellow}        For i As Integer = 0 To 3            g.FillPie(New SolidBrush(seasonColor(i)), New Rectangle(100, 100, 200, 200), seasonAngle(i), seasonAngle(i + 1) - seasonAngle(i))            '饼图中特别需要说明每个季度对应的颜色            g.FillRectangle(New SolidBrush(seasonColor(i)), New Rectangle(360, i * 50 + 80, 60, 40))            '标出每个季度            g.DrawString(seasonName(i), New Font("宋体", 12), New SolidBrush(Color.Black), New Point(450, i * 50 + 90))        Next    End Sub


按下“饼图”按钮时,如下图所示:

需要强调的是FillPie()最后两个关于角度的参数:
第1个角度参数(startAngle):扇形起始角度,是构成扇形的第一条边从x轴方向按照顺时针旋转的角度。
第2个角度参数(sweepAngle):扇形第二条边从第一条边按照顺时针方向旋转的角度



由于.net平台下C#和vb.NET很相似,本文也可以为C#爱好者提供参考。

学习更多vb.net知识,请参看vb.net 教程 目录


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