在窗体上绘制一条对角线，在调整窗体大小时重绘

Posted 2023-03-29

【中文标题】在窗体上绘制一条对角线，在调整窗体大小时重绘

【英文标题】：Draw a diagonal line across form that redraws when the form is resized

【发布时间】：2015-12-22 07:30:06

【问题描述】：

我刚开始使用 GDI - 第一行没问题 - 但第二行...... 我想画一条从 (0,0) 到 (MaxWidth,MaxHeight) 的简单对角线。

这是我的代码：

Public Class Form1
    Dim g As Graphics = Me.CreateGraphics
    Dim stift As New Pen(Brushes.Black, 3)

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim x1 = 0, y1 = 0, x2 = Me.Size.Width, y2 = Me.Size.Height
        g.DrawLine(stift, x1, y1, x2, y2)
    End Sub
End Class

但是该行在第一个未更改的表单的 MaxWidth 和 MaxHeight 处结束。 有人知道吗？

【问题讨论】：

摆脱 CreateGraphics 并使用 Paint 事件。此外，使用 ClientSize 作为宽度和高度。

【参考方案1】：

在 Paint() 事件中绘制线条并允许使用 Button 切换的快速示例：

Public Class Form1

    Private x1 As Integer = 0
    Private y1 As Integer = 0
    Private x2 As Integer = 0
    Private y2 As Integer = 0

    Private DrawLine As Boolean = False
    Private stift As New Pen(Brushes.Black, 3)

    Public Sub New()
        InitializeComponent()

        x2 = Me.ClientSize.Width
        y2 = Me.ClientSize.Height
    End Sub

    Private Sub Form1_SizeChanged(sender As Object, e As EventArgs) Handles MyBase.SizeChanged
        x2 = Me.ClientSize.Width
        y2 = Me.ClientSize.Height
        Me.Refresh()
    End Sub

    Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles MyBase.Paint
        If DrawLine Then
            Dim g As Graphics = e.Graphics
            g.DrawLine(stift, x1, y1, x2, y2)
        End If
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        DrawLine = Not DrawLine
        Me.Refresh()
    End Sub

End Class

这种方法允许您从其他地方更改坐标并调用 Refresh() 来更新屏幕。对于不止一行，请考虑使用包含坐标信息的 List()，然后在 Paint() 事件中对其进行迭代。