Showing drawings on a canvas

[wdegler]

I have something like the following in a loop (containing much activity):

Canvas1.DrawPath(Path1,Colors.Yellow,False,1).

None of the paths appear until the loop is finished. I have tried using DoEvents although this does not seem to involve an event. I don't know what I would apply "Invalidate" to in case that is what is needed.

How can I make the paths appear immediately after the DrawPath calls during each pass?

 

[stevel05]

You need to invalidate the object that you attached the canvas to.

 

[wdegler]

I have tried it but ...

Thank you, Steve, for your response.

I attached Cnv (the canvas) to Activity and then passed Cnv to the code module where the drawing takes place. However, I am not able to invalidate Activity from there. I have tried attaching Cnv to a panel and even to a label and passing these along with Cnv to the code module. The only time I see ANY drawing is when I use Activity and then, only AFTER the loop is finished.
I could put all this code into the Activity module but it is large already.

Suggestions?

 

[stevel05]

You should be able to pass the activity to the sub module in the same way. Then invalidate that in the module.

Steve

 

[wdegler]

This suggestion helped ...

Thank you. Your suggestion helped:

I passed something like
Act as Activity
to my code module and then used Act.Invalidate there to force drawing. This works!

Now, all I need is to later remove all drawing. I have tried the following to no avail:

1) Redrawing in the background color (works for DrawPath but not DrawText).

2)
For I = 0 To Activity.NumberOfViews - 1
Dim V As View
V = Activity.GetView(I)
V.Visible = False
Next

3)
For I = 0 To Activity.NumberOfViews - 1
Activity.RemoveViewAt(I)
next

4)
I even tried calling Activity_Create(False) but that involves some
ugly additional steps.

Can you help with this?

 

[klaus]

What do you want to do, remove the drawings or remove the views ?
Remove the drawings:

Dim rect1 As Rect
rect1.Initialize(0, 0, 100%x, 100%y)
Canvas1.DrawRect(rect1, BackgroundColor, True , 1)

Remove all views:

For I = Activity.NumberOfViews - 1 To 0 Step -1 
  Activity.RemoveViewAt(I)
Next

 

[wdegler]

Your first method works! Thanks for your help

Your first suggestion, to blot out the drawings, works well so I am using it. I forgot that rectangles are easily filled.

I had already tried your second suggestion but that didn't work for DrawText and it would only work for DrawPath when I had a breakpoint set between drawing and erasing with the background color; neither delays nor timers helped.

Thanks for your help; I'm moving forward again!