ios - when re-render layout of UIView, the draw function is not triggered -


i using xcode 8.1

i subclass uiview:

class drawingview: uiview {    override func draw(_ rect: cgrect) {         super.draw(rect)         print("drawing...")    }     override func touchesmoved(_ touches: set<uitouch>, event: uievent?) {       // re-renader layout when finger moves       setneedslayout()       super.touchesmoved(touches, with: event)    } }

when run app, draw(...) function above called once when app launching. (i saw print message)

then, finger move on screen, expected draw(...) should called every finger movement (since called setneedslayout()), draw(...) function never called. why?

to trigger view re-draw, call setneedsdisplay(), instead of setneedslayout()


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