In Flex, how can I get the dimensions of a childless canvas component at runtime?

Question

One of my components looks like this:

<mx:Canvas id="grid" width="100%" height="100%"></mx:Canvas>

On creationComplete, I load some spirte that I want to scale and position based on the dimensions of the canvas to create a custom grid layout, but when I access the dimensions of 'grid' I get 0 and 0. Is there any way to get the dimensions without assigning absolute values?

Answer 1

I can't check this at the moment but can you access the measuredHeight and measuredWidth?

Answer 2

My understanding is that unless the Canvas contains one or more DisplayObject children, it will always report its width and height properties as 0, regardless of the percentage sizings you may have applied to it.

You could always add an empty dummy DisplayObject to the Canvas, but that wouldn't be very elegant. Depending on how you've planned to implement your custom grid, it's possible you'll have to rethink the design...

Answer 3

Is it possibly created but not yet displayed (e.g. visible)? Since final size and shape is derived, it doesn't happen until the thing actually needs to be drawn. Width and height are documented to be the values actually in use - there are even events for when they change.

Worst case, try trapping it out in the canvas Resize event.

Answer 4

This is driving me crazy too. I am adding a label and a datagrid to a VBox container. Both of them have height = 0, width = 0. And I Want to get their dimensions so that I can resize the parent container.

Answer 5

have you tried binding the width and height of the Canvas to its parent? If it is 100%, than it will have the same size as its parent and you could either bind or size your Sprite (UIComponent) based on the parent container of the Canvas.