cpcircle.vb

苏金明编写的《用VB.NET和VC#.NET开发交互式CAD系统》一书的源代码

Imports System.Math

Public Class CPCircle
    Inherits DrawCircle

    Private m_Center, m_pCircle As PointF

    '圆心
    Public Property Center() As PointF
        Get
            Return m_Center
        End Get
        Set(ByVal newValue As PointF)
            m_Center = newValue
        End Set
    End Property

    '圆上一点
    Public Property pCircle() As PointF
        Get
            Return m_pCircle
        End Get
        Set(ByVal newValue As PointF)
            m_pCircle = newValue
        End Set
    End Property

    '半径属性，只读
    Public ReadOnly Property Radius() As Single
        Get
            Dim r As Single
            r = DistPtoP(m_Center, m_pCircle)
            Return r
        End Get
    End Property

    '无参构造函数
    Public Sub New()
    End Sub

    '构造函数，用已知的两点构造圆
    Public Sub New(ByVal pCenter As PointF, ByVal pCir As PointF)
        m_Center = pCenter
        m_pCircle = pCir
    End Sub

    '计算点与点之间的距离
    Private Function DistPtoP(ByVal p1 As PointF, _
                   ByVal p2 As PointF) As Single
        Dim dx As Single
        Dim dy As Single
        dx = p2.X - p1.X
        dy = p2.Y - p1.Y
        Return Sqrt((dx * dx) + (dy * dy))
    End Function

    '绘圆
    Public Overrides Sub Draw(ByVal g As Graphics)
        g.DrawEllipse(Pens.Red, m_Center.X - Radius, _
              m_Center.X - Radius, Radius * 2, Radius * 2)
    End Sub
End Class