Flex in the Canvas is the most commonly used containers, but the canvas is not the use of graphics makes them very comfortable to use. When the container used or set the backgroundColor of this attribute, the object re-use graphics to draw lines or to draw graphics on the will not be displayed because the graphics layer and backgroundColor using the same level, so graphics rendering will be blocked can not be displayed.
 
I have often posted out of the two solutions:
 
Method 1:
 
canvas of backgroundColor is not set, this is the most direct way, but if have to use the background color does not.
 
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Method 2:
 
You can use the UIComponent to solve this problem, although annoying points, but it is pretty good.
 
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