vb.net GDI+

当然是全部重画。

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层只不过是制图软件弄出来的一个方便的东西而已。

就像你画画，画上去如果你要擦掉当然是擦到底色咯。（当然GDI+也可以像你画画一样只擦一部分）

GDI+时钟我写过一个VB6的。代码详见我博客。地址显然百度不让贴上= =。所以你可以看下我的资料。

你可以模拟层，就是把所有绘制信息都保存起来。你的流程应当是：

如果要绘制了，更新绘制信息（可以是数组啥的。），交给一个Draw过程

Draw过程：根据绘制信息，全部绘制。

By vIstaswx ,before junior school graduation exam.

vb.net开发简单的时钟程序？？高手救救我！

就

是

这

个

了

！

Hand类的代码：

Public MustInherit Class Hand

Protected gp As GraphicsPath = New GraphicsPath()

Protected gpBase As GraphicsPath = Nothing

Protected midX As Integer = 150 ‘默认的窗体

Protected midY As Integer = 150 ‘中心位置

‘构造器，得到窗体中心位置

Public Sub New(ByVal theForm As Form1)

midX = (theForm.ClientRectangle.Left + theForm.ClientRectangle.Right) / 2

midY = (theForm.ClientRectangle.Top + theForm.ClientRectangle.Bottom) / 2

End Sub

MustOverride Sub Transform(ByVal d As DateTime)

‘绘制指针路径

Overridable Sub Draw(ByVal g As Graphics)

Dim aPen As Pen = New Pen(Brushes.Black, 4F)

g.DrawPath(aPen, gp)

g.FillPath(Brushes.Black, gp)

aPen.Dispose()

End Sub

‘使用矩阵实现路径（gp）的旋转

Public Sub Rotate(ByVal angle As Double)

gp = CType(gpBase.Clone(), GraphicsPath)

Dim mTransform As Matrix = New Matrix()

mTransform.RotateAt(CType(angle,Single),NewPointF(midX,midY))

gp.Transform(mTransform)

End Sub

End Class

为了节省篇幅，上面的代码省略了引入命名空间的语句。

下面是分针（MinuteHand）类的定义：

Public Class MinuteHand

Inherits Hand

‘构造器，生成绘制分针的路径（gp）

Public Sub New(ByVal myForm As Form1)

MyBase.New(myForm)

gp.AddLine(midX, midY, midX, 45)

gp.AddLine(midX, 45, midX - 3, 50)

gp.AddLine(midX - 3, 50, midX + 3, 50)

gp.AddLine(midX + 3, 50, midX, 45)

gpBase = CType(gp.Clone(), GraphicsPath)

End Sub

‘Transform方法取得系统当前时间，并旋转时钟指针。

Public Overrides Sub Transform(ByVal d As DateTime)

Dim minuteTime As Double = (CDbl(d.Minute) + CDbl(d.Second / 60))

Dim angle As Double = (CDbl(minuteTime) / 60) * 360

Rotate(angle)

End Sub

End Class

对所有的指针旋转的方法都是相同的，因此在基类中实现。由于时针和秒针的实现与分针相似，所不同者，只在于构造器中绘制的指针路径不同和Transform方法中转动的角度不同，在这里就不在赘述了。

另外还需要提一下的是画时钟表面的代码，时钟表面用ClockFace类来实现。这个类首先画一个圆代表时钟，然后画上米老鼠的图案，最后在相应的位置画上数字1～12代表12个小时。

Public Sub Draw(ByVal g As Graphics)

DrawClockFace(g)

DrawImage(g)

DrawNumbers(g)

DrawPin(g)

End Sub

下面是ClockFace类的属性：

Private ClockRectangle As Rectangle

Private ClockFont As Font = New Font("Arial", 12)

Private midPoint As Point

Private ClockImage As Bitmap

Private Const IMAGEX As Integer = 50

Private Const IMAGEY As Integer = 50

DrawClockFace方法用来画时钟表面：

Private Sub DrawClockFace(ByVal g As Graphics)

g.FillEllipse(Brushes.White, ClockRectangle.Left + 10, ClockRectangle.Top + 10, ClockRectangle.Width - 20, ClockRectangle.Height - 20)

g.DrawEllipse(Pens.Black, ClockRectangle.Left + 10, ClockRectangle.Top + 10, ClockRectangle.Width - 20, ClockRectangle.Height - 20)

End Sub

然后用Graphics对象的DrawImage方法画出米老鼠的图片：

Private Sub DrawImage(ByVal g As Graphics)

Dim nWidth As Integer = ClockImage.Width

Dim nHeight As Integer = ClockImage.Height

Dim destRect As Rectangle = New Rectangle(midPoint.X - IMAGEX / 2, midPoint.Y - IMAGEY / 2, IMAGEX, IMAGEY)

g.DrawImage(ClockImage, destRect)

End Sub

数字在时钟上的位置是用sin和cos函数计算的：

Private Sub DrawNumbers(ByVal g As Graphics)

Dim count As Integer = 1

Dim a As Double

For a = 0 To 2 * Math.PI Step 2 * Math.PI / 12

Dim x As Double = (ClockRectangle.Width - 70) / 2 * Math.Cos(a - Math.PI / 3) + (ClockRectangle.Width - 70) / 2 + 25

Dim y As Double = (ClockRectangle.Width - 70) / 2 * Math.Sin(a - Math.PI / 3) + (ClockRectangle.Width - 70) / 2 + 20

g.DrawString(Convert.ToString(count), ClockFont, Brushes.Black, CType(x, Single), CType(y, Single), New StringFormat())

count += 1

Next

End Sub

最后是窗体文件（Form1.vb）:

Public Class Form1

Inherits System.Windows.Forms.Form

Private MyMinuteHand As MinuteHand

Private MyHourHand As HourHand

Private MySecondHand As SecondHand

Private TheClockFace As ClockFace

Private FirstTick As Boolean = False

‘在窗体的OnPaint事件中取得Graphics对象

Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)

If (FirstTick = False) Then Exit Sub

Dim g As Graphics = e.Graphics

TheClockFace.Draw(g)

MyHourHand.Draw(g)

MyMinuteHand.Draw(g)

MySecondHand.Draw(g)

TheClockFace.DrawPin(g)

End Sub

‘计时器事件

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

MySecondHand.Transform(DateTime.Now)

MyHourHand.Transform(DateTime.Now)

MyMinuteHand.Transform(DateTime.Now)

FirstTick = True

Invalidate()

怎样用vb.net作一个指针转动的钟表?(可设置时间日期,有闹铃功能)

你需要会用GDI+,也就是那个System.Drawing命名空间下的类.

给你说个思路,设Timer,到时间就用Form.Invalidate()函数重画窗口,在重画窗口的Form_Paint事件下面编写代码得到当前时间,再根据当前时间用GDI+画时钟.

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