Not sure there's really any good solution for doing this. But first of all, why are you disabling a canvas (especially if you need a button in it to still work?)
i have a map component(canvas). on the map comp i had a map control panel.
user shud not select anything on the map unless he searches for a location on the control panel.Once he searches for location and clicks on ok, the map canvas will be enabled..
Okay, that makes more sense. My first thought is taking that child out of the parent. Can you make the control panel a popup? You could also "overlap" the control panel by putting it in the same parent container as the canvas and using an absolute layout (you'd place the canvas tag first in the mxml file), but I tend to avoid doing that sort of thing. This would be the easiest/fastest solution but you lose a little flexibility resorting to an absolute layout (this may or may not be a big deal for you).