我对winforms中的Graphics类没有多少经验。
我只是在草绘阶段（也是我添加的代码）。
我的问题是我正在尝试创建一个面板：clockPanel上面有一些图形，没有抛出异常，但面板（我在UI中可以看到）上没有图形。试图寻找例子但我无法在我的代码中找到错误或遗漏的东西。对于那些有图形经验的人来说，这可能很简单。
谢谢你的时间考虑。
VB代码： 通过实例将'clockpanel'面板添加到其他面板（'secondaryPannel'）到GoalsClock类
Public Class ManagersTab
...
Public Sub BuiledDashBoard()
...
Dim p As GoalsClock = New GoalsClock(100, 100, 0.8)
p.Create()
p.clockPanel.Location = New Point(200, 100)
secondaryPannel.Controls.Add(p.clockPanel)
...
End Sub
...
End Class
Create（）方法是最相关的部分：
Class GoalsClock
Private Gclock As Graphics
Private clockWidth As Int16
Private clockHeight As Int16
Private xPos As Int16
Private yPos As Int16
Public clockPanel As Panel
Private panelColor As Color
Private PercentTextColor As Color
' rectangles to store squares
Protected OuterRect As Rectangle
Protected InnerRect As Rectangle
Protected InnerStringBrush As Brush
Protected InnerStringColor As Color
Protected InnerStringFontSize As Byte
' inner square
Private InnerSquarePen As Pen
Private InnerSquarePen_Color As Color
Private InnerSquarePen_Width As Byte
' outer square
Private OuterSquarePen As Pen
Private OuterSquarePen_Color As Color
Private OuterSquarePen_Width As Byte
Private _PercentOfGoals As Single ' to calculate the goals deg arc
Public Property PercentOfGoals() As Single
Get
Return _PercentOfGoals * 100
End Get
Private Set(ByVal value As Single)
If value <= 1.0F Then
_PercentOfGoals = value
Else
value = 0
End If
End Set
End Property
Sub New(ByVal clockWidth As Int16, ByVal clockHeight As Int16, ByVal GoalsPercent As Single)
Me.clockWidth = clockWidth
Me.clockHeight = clockHeight
PercentOfGoals = GoalsPercent
' values for test
xPos = 0
yPos = 0
InnerStringFontSize = 12
OuterSquarePen = New Pen(Color.Gray)
InnerSquarePen = New Pen(Color.Cyan)
OuterSquarePen_Width = 23
InnerSquarePen_Width = 15
End Sub
''' <summary>
'''
''' create graphics of the goals clock on clockPanel
''' </summary>
''' <remarks></remarks>
Public Sub Create()
' panel
clockPanel = New Panel()
clockPanel.Size = New Size(clockWidth, clockHeight)
clockPanel.BackColor = Color.Beige
Gclock = clockPanel.CreateGraphics()
' create outer rectangle
OuterRect = New Rectangle(xPos, yPos, clockWidth, clockHeight)
' create inner rectangle
Dim w, h, x, y As Integer
getInnerRectSizeAndLocation(w, h, x, y)
InnerRect = New Rectangle(x, y, w, h)
' draw goals string inside inner rect
InnerStringBrush = Brushes.Cyan
Gclock.DrawString(getPercentString(), New Font("ARIAL", InnerStringFontSize, FontStyle.Bold), InnerStringBrush, InnerRect)
' create outer square
OuterSquarePen = New Pen(OuterSquarePen_Color, OuterSquarePen_Width)
Gclock.DrawArc(OuterSquarePen, OuterRect, 1.0F, 360.0F)
' create inner square
InnerSquarePen = New Pen(InnerSquarePen_Color, InnerSquarePen_Width)
Dim sweepAngle As Short = getSweepAngleFromGoalsPercent()
Gclock.DrawArc(InnerSquarePen, OuterRect, -90.0F, sweepAngle)
End Sub
Private Sub getInnerRectSizeAndLocation(ByRef w As Integer, ByRef h As Integer, ByRef x As Integer, ByRef y As Integer)
' values for test
w = 40
h = 40
x = 64
y = 65
End Sub
Private Function getPercentString() As String
Return PercentOfGoals.ToString() & "%"
End Function
Private Function getSweepAngleFromGoalsPercent() As Single
' value for test
Return 0.0F
End Function
End Class
答案 0 :(得分：1)
您必须订阅小组Paint event并在那里执行所有绘图。 AddHandler statement用于动态订阅事件。
<HTML>
<HEAD>
<TITLE>Unauthorized</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF" TEXT="#000000">
<H1>Unauthorized</H1>
<H2>Error 401</H2>
</BODY>
</HTML>
课程不会存储您绘制的内容的任何信息，因此当您的面板重新绘制时，您之前绘制的所有内容都将消失，除非您再次绘制它。这就是Graphics事件发挥作用的地方：每次重新绘制面板时都会引发它，在Paint中传递Graphics类的实例，这样你就可以将你的东西绘制到小组再次。
PaintEventArgs正如您也可能已经看到我在Public Sub Create()
' panel
clockPanel = New Panel()
clockPanel.Size = New Size(clockWidth, clockHeight)
clockPanel.BackColor = Color.Beige
' subscribe to the panel's paint event
AddHandler clockPanel.Paint, AddressOf clockPanel_Paint
End Sub
Private Sub clockPanel_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs)
Dim Gclock As Graphics = e.Graphics 'Local variable only, as the Graphics object might change.
' create outer rectangle
OuterRect = New Rectangle(xPos, yPos, clockWidth, clockHeight)
' create inner rectangle
Dim w, h, x, y As Integer
getInnerRectSizeAndLocation(w, h, x, y)
InnerRect = New Rectangle(x, y, w, h)
' draw goals string inside inner rect
InnerStringBrush = Brushes.Cyan
Gclock.DrawString(getPercentString(), New Font("ARIAL", InnerStringFontSize, FontStyle.Bold), InnerStringBrush, InnerRect)
' create outer square
OuterSquarePen = New Pen(OuterSquarePen_Color, OuterSquarePen_Width)
Gclock.DrawArc(OuterSquarePen, OuterRect, 1.0F, 360.0F)
' create inner square
InnerSquarePen = New Pen(InnerSquarePen_Color, InnerSquarePen_Width)
Dim sweepAngle As Short = getSweepAngleFromGoalsPercent()
Gclock.DrawArc(InnerSquarePen, OuterRect, -90.0F, sweepAngle)
End Sub
事件中不断重新声明新的Gclock变量。这是因为用于绘制面板的Paint实例可能会发生变化，因此您不应该将其存储时间超过Graphics事件持续时间（因此我强烈建议您删除声明在你班上的顶部）。