[VB.NET] Form Redraw?

[Pox]

this is probably extremely easy to fix, but here goes.

i'm using a graphicspen to draw on a picturebox. however, every time i minimize/move another window oveer it, it disappears. i seem to remember a .ReDraw property in VB6, but it's not there. What's the .Net equivelant?

(Visual Basic, VS.NET 2003)

[$phinX]

  AMDPOX said:

this is probably extremely easy to fix, but here goes.

i'm using a graphicspen to draw on a picturebox.  however, every time i minimize/move another window oveer it, it disappears.  i seem to remember a .ReDraw property in VB6, but it's not there.  What's the .Net equivelant?

(Visual Basic, VS.NET 2003)

586306143[/snapback]

.Paint() usually forces whatever component it is to redraw itself.

[Max-Eclipse]

  AMDPOX said:

this is probably extremely easy to fix, but here goes.

i'm using a graphicspen to draw on a picturebox.? however, every time i minimize/move another window oveer it, it disappears.? i seem to remember a .ReDraw property in VB6, but it's not there.? What's the .Net equivelant?

(Visual Basic, VS.NET 2003)

586306143[/snapback]

.Invalidate() forces a redraw

If you use .Paint() you calling the sub directly, which isn't a good idea in this situation. It shouldn't hurt anything, but it's just better practice to use .Invalidate().

[Pox]

i've tried:

    Private Sub Form1_LocationChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.LocationChanged
        pD.Invalidate()
    End Sub

    Private Sub Form1_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.LostFocus
        pD.Invalidate()
    End Sub

and

    Private Sub Form1_LocationChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.LocationChanged
        Form1.Invalidate()
    End Sub

    Private Sub Form1_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.LostFocus
        Form1.Invalidate()
    End Sub

where pD is the picturebox. But it appears that b the Invalidate are simply clearing the the picturebox. Paint() seems to be an event, not a method....?

[azcodemonkey]

  AMDPOX said:

this is probably extremely easy to fix, but here goes.

i'm using a graphicspen to draw on a picturebox.  however, every time i minimize/move another window oveer it, it disappears.  i seem to remember a .ReDraw property in VB6, but it's not there.  What's the .Net equivelant?

(Visual Basic, VS.NET 2003)

586306143[/snapback]

Are you drawing on the picture box during its paint event? If not, do so. Then, in your form's resize and/or move event, invalidate the picturebox.

Edited August 2, 2005 by weenur

[Pox]

i have the drawing commands in the MouseDown and MouseMove events... i dont see how i could put them in .Paint() and leave the functionality the same.. :(

[Linkinfamous]

Either refresh or invalidate/update should work, right?

Edited August 2, 2005 by Dayon

[azcodemonkey]

  AMDPOX said:

i have the drawing commands in the MouseDown and MouseMove events... i dont see how i could put them in .Paint() and leave the functionality the same.. :(

586311835[/snapback]

Ah, ok. Makes sense now.

You need to draw to an image to preserve state. Create a class member variable that is an Image or Bitmap, and base it on the pictureBox.

Do this in the form constructor(New sub)

Dim g1 as Graphics = Graphics.FromHwnd(picturebox1.Handle)

' declared at the class level
picImg = new Bitmap(pictureBox1.ClientRectangle.Width, pictureBox1.ClientRectangle.Height, g1)

Handle the paint event for your picturebox and use the Graphics object to draw the image.

private sub PicPaint(sender as object, e as PaintEventArgs) handles pictureBox1.Paint

  e.Graphics.DrawImage(picImg, 0, 0)

end sub

Then in your mouse handler(up, i assume), draw on the image

  	end = new PointF(e.X, e.Y);

  	dim g2 as Graphics = Graphics.FromImage(picImg)
  	g2.DrawLine(Pens.Black, begin, end) ' or whatever
  	pictureBox1.Invalidate(false)

[benj]

I'm a newbie and pretty confused at this point. I have searched quite a bit for a solution to the same problem and have not been able to understand the code you posted.

I have a form with PictureBox1 and Button1 on it. My code looks like this:

Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button5.Click
     g = PictureBox1.CreateGraphics() 
     Dim g As Graphics
     Dim pRed As New Pen(Color.Red, 2)
     g.DrawLine(pRed, x1, y1, x2, y2)
End Sub

with x1, y1, x2, y2 being coordinates of the start and end of the line. That part works, but much like AMDPOX describes, when I minimize the window, the line disappears. I see that weenur has given him a reply with some code, but I guess I don't fully understand it.

When you say

  Quote

Do this in the form constructor(New sub)

I understand what the form constructor is, but not sure how I should make the New sub.

Also, I'm not sure what you mean by

  Quote

' declared at the class level

.

Could you show me what I should do with my code, and maybe paste the entire code of the form from top to bottom? I think that would help me understand the placement of each piece of code.

Again, I'm a newbie, so thank you for your patience with my 'newbieness' :)