捕获矩形

Question

这有效。它利用一个简单的矩形面板上：

Dim g As Graphics 
    Dim fPen As Pen 
    g = aPanel.CreateGraphics() 

    fPen = New Pen(Color.Blue) 
    Dim PointX As Point = New Point(10, 20) 
    Dim PointY As Point = New Point(50, 50) 

    g.DrawRectangle(fPen, PointY.X, PointY.Y, 50, 50) 

一切都是对象 - 但我如何引用这ractangle？
我希望在代码中稍后创建椭圆时（即在矩形中绘制椭圆）时，使用此矩形作为参数之一 - 为什么我不能执行以下操作？

Dim g As Graphics 
    Dim fPen As Pen 
    g = aPanel.CreateGraphics() 

    fPen = New Pen(Color.Blue) 
    Dim PointX As Point = New Point(10, 20) 
    Dim PointY As Point = New Point(50, 50) 

    Dim r As Rectangle 
    r = New Rectangle(g.DrawRectangle(fPen, PointY.X, PointY.Y, 50, 50)) '<<<errors here 
    g.DrawEllipse(fPen, r) 

Answer 1

声明你的矩形，并使用其值：

Dim r As New Rectangle(10, 50, 50, 50) 

g.DrawRectangle(fPen, r.Location.X, r.Location.Y, r.Width, r.Height) 
g.DrawEllipse(fPen, r) 

Answer 2

的Graphics对象上的DrawRectangle method，因为它是一个Sub不返回任何值。

您首先必须创建Rectangle的实例，您可以稍后使用该实例绘制矩形和椭圆。

Dim pointY As New Point(50, 50) 
Dim rectSize As New Size(50, 50) 
Dim rect As New Rectangle(pointY, rectSize) 

g.DrawRectangle(fPen, rect) 
g.DrawEllipse(fPen, rect)