使用给定的大小和 X/Y POS 在 VB.NET 中绘制一个圆会产生意想不到的结果

编程问答 2022-05-27

问题描述

我正在制作一个应用程序，当给定直径的输入以及圆的 X 和 Y 通孔的中心点时，该应用程序会绘制一个圆。 PictureBox 中的 TextBox。

当我运行应用程序并输入恒定的 X 和 Y 但缓慢增加/减小圆的直径时，即使 X 和 Y 位置不变，圆也开始随机移动位置。有时，如果我在任何变量（X Pos、Y Pos 和直径）未更改时刷新 PictureBox，即使没有任何更改，圆圈也会无缘无故地移动...

这是要重现的代码：

这些变量已经声明：

    Dim beginSCircleXPos As Integer 'What the user put into as the circle's center for X
    Dim beginSCircleYPos As Integer 'What the user put into as the circle's center for y

    Dim sCircleXPos As Integer 'Top-Left point of the circle in X
    Dim sCircleYPos As Integer 'Top-Left point of the circle in Y
    Dim sCircleDiameter As Integer 'The diameter that user put into.


    Dim sCenterPointX As Integer 'Variables will be updated later
    Dim sCenterPointY As String

PictureBox 的 Paint 事件

beginSCircleXPos = TextBox1.Text
        beginSCircleYPos = TextBox2.Text

        sCircleXPos = beginSCircleXPos - sCircleDiameter / 2
        sCircleYPos = beginSCircleYPos - sCircleDiameter / 2


        sCircleDiameter = TextBox3.Text


        Using path As New GraphicsPath
            path.AddEllipse(sCircleXPos,sCircleYPos,sCircleDiameter,sCircleDiameter)
            sCenterPointX = sCircleXPos + sCircleDiameter / 2
            sCenterPointY = sCircleYPos + sCircleDiameter / 2

            Using brush As New PathGradientBrush(path)
                brush.CenterPoint = New PointF(sCenterPointX,sCenterPointY) 
                brush.CenterColor = Color.FromArgb(0,Color.Orange)
                brush.SurroundColors = {Color.Orange}
                brush.FocusScales = PointF.Empty

                e.Graphics.FillRectangle(brush,sCircleXPos,sCircleDiameter)
            End Using
        End Using

值得注意的是，PictureBox 是通过点击带有 PictureBox1.Refresh() 命令的按钮来刷新的。

我该如何解决这个问题，以便中心点的输入和 X/Y 值每次都能得到正确且恒定的答案？

编辑：

  beginSCircleXPos = Convert.ToSingle(TextBox1.Text)
        beginSCircleYPos = Convert.ToSingle(TextBox2.Text)


        sCircleXPos = beginSCircleXPos - sCircleDiameter / 2
        sCircleYPos = beginSCircleYPos - sCircleDiameter / 2


        sCircleDiameter = Convert.ToSingle(TextBox3.Text)






        Using path As New GraphicsPath
            path.AddEllipse(sCircleXPos,sCircleDiameter)
            End Using
        End Using
    ```
Variables:

将 beginSCircleXPos 调暗为单个 Dim beginSCircleYPos 为单个

Dim sCircleXPos As Single
Dim sCircleYPos As Single
Dim sCircleDiameter As Single


Dim sCenterPointX As Single
Dim sCenterPointY As Single

解决方法

我没有仔细看你的代码。我仍然有我提供的代码来回答你之前的问题，所以我用它作为基础，只是像我自己那样修改它。我使用 Timer 每秒重新绘制一次 PictureBox 以使其更简单。这就是我最终的结果：

Private Sub PictureBox1_Paint(sender As Object,e As PaintEventArgs) Handles PictureBox1.Paint
    Dim centreX As Single
    Dim centreY As Single
    Dim diameter As Single

    If Single.TryParse(TextBox1.Text,centreX) AndAlso
       Single.TryParse(TextBox2.Text,centreY) AndAlso
       Single.TryParse(TextBox3.Text,diameter) Then
        Dim radius = diameter / 2.0F
        Dim bounds As New RectangleF(centreX - radius,centreY - radius,diameter,diameter)

        Using path As New GraphicsPath
            path.AddEllipse(bounds)

            Using brush As New PathGradientBrush(path) With {.CenterPoint = New PointF(centreX,centreY),.CenterColor = Color.FromArgb(0,Color.Orange),.SurroundColors = {Color.Orange},.FocusScales = PointF.Empty}
                e.Graphics.FillRectangle(brush,bounds)
            End Using
        End Using
    End If
End Sub

Private Sub Timer1_Tick(sender As Object,e As EventArgs) Handles Timer1.Tick
    PictureBox1.Invalidate()
End Sub

它似乎对我来说正如预期的那样工作。如果 TextBoxes 中的一个或多个不包含有效数字，则不会绘制任何内容，否则会在预期的位置和方式绘制分级圆。如果我设置中心坐标，然后改变直径，绘制的圆将保持一个恒定的中心，但会按预期增长和缩小。

如果需要，您显然可以使用 Button.Click 而不是 Timer.Tick。

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