vb.net DrawArc 不会在 Picturebox 中刷新

Question

我正在尝试显示在图片框中绘制的动画弧线。我无法在每个循环（每 100 度）处绘制弧线。油漆仅在子例程结束时触发，最终弧度为 300 度。如何在每个循环中强制刷新图片框？这是我的代码和表格。

 Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint

    Dim pen As New Pen(Color.Red, 1)
    Dim r As Integer = 100

    'Delay(2)

    Do Until r > 300
        e.Graphics.DrawArc(pen, 50, 50, 50, 50, 270, r)           ' pen style, x position, y postion, width, height, start point degrees, arc degrees
        ListBox1.Items.Add(r)
        ListBox1.SelectedIndex = ListBox1.Items.Count - 1
        r = r + 100
        Delay(1)
    Loop

    e.Dispose()
    pen.Dispose()
    ListBox1.Items.Add("Done")

End Sub

我试过在循环中使用 picturebox1.refresh()、update()、invalidate() 但没有成功。

Answer 1

如果改用计时器会怎样？

Imports System.Timers.Timer

Public Class Form1
Dim tmr1 As New Timer
Dim r As Int32 = 0

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
    Me.DoubleBuffered = True

    AddHandler tmr1.Tick, AddressOf tmr1_Tick
    With tmr1
        .Interval = 1000
        .Start()
    End With
End Sub

Private Sub tmr1_Tick(ByVal sender As Object, ByVal e As EventArgs)
    If r < 300 Then
        r += 100
        ListBox1.Items.Add(r)
        ListBox1.SelectedIndex = ListBox1.Items.Count - 1
        Me.PictureBox1.Invalidate()
    Else
        ListBox1.Items.Add("Done")
        tmr1.Stop()
    End If
End Sub

Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
    Dim pen As New Pen(Color.Red, 1)
    Dim g As Graphics = e.Graphics
    Debug.WriteLine("PictureBox1: " & r)
    g.DrawArc(pen, 50, 50, 50, 50, 270, r)           ' pen style, x position, y postion, width, height, start point degrees, arc degrees

    pen.Dispose()
End Sub
End Class

vb.net DrawArc 不会在 Picturebox 中刷新

vb.net DrawArc won't refresh in Picturebox

vb.net

drawing

picturebox