Question

这很有效。它在面板上绘制一个简单的矩形：

    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 - 但我如何引用这个ractangle？
我想在稍后在代码中创建一个椭圆时使用这个矩形作为参数之一（即在矩形中绘制椭圆） - 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它的值：

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

Graphics对象上的DrawRectangle method，不会返回任何值，因为它是Sub。

首先必须创建Rectangle的实例，稍后您可以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)

捕获一个矩形

2 个答案: