送分问题!!!我在窗体上利用鼠标动态的画矩形,就像QQ截图的矩形选框那样.可是怎么清除之前画的矩形留下的痕迹?
我试着用me.refresh()清除痕迹,是能清除,但是窗体(加载过背景图片的)却闪烁的十分严重!
我是在MOUSEMOVE事件下画矩形的,鼠标每动一点就闪得很厉害!
请问有什么方法可以解决这个闪烁问题?
或者有什么好的方法,敬请高手指教.
初学VB.NET,请大家务必解释详细点!谢谢!
[解决办法]
Public Class Form1
Private rectList As New List(Of Rectangle)
Private pt As Point
Private bmpOld As Bitmap
Private Sub Form1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown
pt.X = e.X
pt.Y = e.Y
End Sub
Private Sub Form1_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseMove
If e.Button = Windows.Forms.MouseButtons.Left Then
Dim g As Graphics = Graphics.FromImage(Me.BackgroundImage)
'擦除之前绘制的内容
Dim brush As New SolidBrush(Me.BackColor)
g.FillRectangle(brush, Me.ClientRectangle)
brush.Dispose()
'绘制之前的，包括当前的内容
Dim x, y, w, h As Integer
x = Math.Min(pt.X, e.X)
y = Math.Min(pt.Y, e.Y)
w = Math.Abs(pt.X - e.X)
h = Math.Abs(pt.Y - e.Y)
For i As Integer = 0 To rectList.Count - 1
g.DrawRectangle(Pens.Blue, rectList(i))
Next
g.DrawRectangle(Pens.Blue, x, y, w, h)
g.Dispose()
g = Me.CreateGraphics()
g.DrawImage(Me.BackgroundImage, 0, 0)
g.Dispose()
End If
End Sub
Private Sub Form1_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseUp
Dim x, y, w, h As Integer
x = Math.Min(pt.X, e.X)
y = Math.Min(pt.Y, e.Y)
w = Math.Abs(pt.X - e.X)
h = Math.Abs(pt.Y - e.Y)
rectList.Add(New Rectangle(x, y, w, h))
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.BackgroundImage = New Bitmap(Width, Height)
End Sub
Private Sub Form1_ResizeEnd(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.ResizeEnd
If bmpOld Is Nothing Then Return
Me.BackgroundImage = New Bitmap(Width, Height)
Dim g As Graphics = Graphics.FromImage(Me.BackgroundImage)
g.DrawImage(bmpOld, 0, 0)
g.Dispose()
bmpOld.Dispose()
bmpOld = Nothing
End Sub
Private Sub Form1_ResizeBegin(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.ResizeBegin
If BackgroundImage Is Nothing Then Return
bmpOld = Me.BackgroundImage
End Sub
Private Sub Form1_Resize(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Resize
Me.BackgroundImage = Nothing
End Sub
Private Sub Form1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint
If bmpOld Is Nothing Then Return
e.Graphics.DrawImage(bmpOld, 0, 0)
End Sub
End Class
