Invalidating Canvas in a outside class

Getting Started
1

Hi, i’m new in xojo. does anyone know how can i invalidate my canvas from another class?

2

Hi Amin,
You should have no trouble calling Invalidate on a canvas:

Canvas1.Invalidate( False )

What problem are you actually having?

3

this is great that u r answering my question. im trying to create an animator timer class. but i cant refresh the canvas in my timer class actully i cant pass it to my animator class

4

I actually did a 4-part series on the Xojo blog about building such animations:

5

something like ur animate canvas but more flexible
ive done it before in wxpython

6

actually i read it completely before. ur r using the action event in ur canvas
but my timer is a class inherited from timer that can change the objectvalues using easing time graphs

7

All of that can be easily decoupled from the canvas. My GraffitiAnimator for Desktop is a standalone class that provides updates that can be applied anywhere via events, for instance.

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Alot of the code is the same, it’s just repackaged in a reusable manner. And there’s no shortage of built-in easing functions:

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8

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Great but i have done all this before and converted the python codes to Xojo.

9

OK, well, all you need to do is invalidate your canvas as your animation progresses. Not sure how else I can help, then.

10

my question is how can i invalidate this switchbutton canvas in animator class?

11

Well, you could pass it in as part of your animation operation when you start, make it a property of the animator class, or create an event definition for the animation progress that your Canvas component receives using AddHandler.

12

thanks a lot. but how can i pass it to animator when i try it like this i get nilexceptionerror
animator.MainParent = Me

13

You would set it to an instance of your Animator class. I assume you are creating an instance, so it should look something like this:

var myAnimator as new Animator '// If you don't create a new instance and are instead just declaring a variable or property, it will be nil.
myAnimator.MainParent = me
myAnimator.RunMode = Timer.RunModes.Multiple
14

i have done this all before but i get error. i defined a property of my animator class. should i use New for it in open event?

15

You could instantiate as needed, when you get ready to perform an operation:

if animator = Nil then
  animator = new Animator
end

You could do it in your Canvas subclass’ Opening event:

animator = new Animator

I’d encourage you to use a different name for your property, though.

1 Like
16

thanks alot… i should New it
.thanks for ur support and ur great article that helped me alot getting familiar with this kind of VB like coding

17

Happy to help! Please mark a solution so that others can easily find it in the future, should they need to.

1 Like