关于在PictureBox中绘图，当窗口被掩盖时窗口无法重绘的问题

Question

我用的是vb.net 2010窗体中有一个PictureBox控件和一个Button控件，窗体启动后按Button控件会在PictureBox控件中绘一些线框，当这个窗口被掩盖或窗口尺寸改变后，以前绘的东西都不见了，如何解决？

下面是窗体中的代码，请高手给指点一下哪里有问题，谢谢。

Imports System.Drawing.Drawing2D
Public Class Form1
    Dim BlackPen As Pen
    Dim gr As Graphics
    Dim bm As New Bitmap(880, 100)
    Dim gPath1 As GraphicsPath
    Dim graph As Graphics
    Dim tempArray(19) As Boolean
    Dim myArray As Point()
    Sub New()
        ' 此调用是设计器所必需的。
        InitializeComponent()
        ' 在 InitializeComponent() 调用之后添加任何初始化。
        gr = PictureBox1.CreateGraphics
        BlackPen = New Pen(Brushes.Red, 1.7)
        graph = Graphics.FromImage(bm)
        graph.SmoothingMode = SmoothingMode.AntiAlias
    End Sub
    Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        PlotData()
    End Sub
    Private Sub PlotData()
        graph.FillRectangle(Brushes.WhiteSmoke, 0, 0, 880, 100) '清除画布
        Dim pen1 As Pen = New Pen(Color.Green, 1.5) '实线
        Dim pen2 As Pen = New Pen(Color.Green, 0.01) '实线
        Dim gPath1 As GraphicsPath = New GraphicsPath '路径1
        Dim gPath2 As GraphicsPath = New GraphicsPath '路径2
        Dim pathRect As New Rectangle '矩形路径
        For i As Integer = 20 To 850 Step 42 '循环20次
            pathRect = New Rectangle(i, 20, 42, 26) '创建矩形路径的尺寸
            gPath1.AddRectangle(pathRect) '添加矩形
            gPath2.AddEllipse(i + 6, 24, 7, 7) '添加左边圆形
            gPath2.AddEllipse(i + 29, 24, 7, 7) '添加右边圆形
            graph.DrawLine(pen1, i + 7, 38, i + 12, 38) '画正号 横
            graph.DrawLine(pen1, CSng(i + 9.5), CSng(35.5), CSng(i + 9.5), CSng(40.5)) '画正号 负
            graph.DrawLine(pen1, i + 30, 38, i + 35, 38) '画负号
            graph.DrawPath(pen1, gPath1) '画路径1
            graph.DrawPath(pen2, gPath2) '画路径2
        Next
        PictureBox1.CreateGraphics.DrawImage(bm, 0, 0)
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        PlotData()
    End Sub
End Class

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myriceme

Answer 1

将这一行：PictureBox1.CreateGraphics.DrawImage(bm, 0, 0)

替换为下面一行即可

PictureBox1.Image = bm

是这样的吗？

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学无止境

Answer 2

谢谢 学无止境 的指点，问题解决。

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myriceme