What control events start and end highlight state of UIButton

Question

I am creating piano-like view with UIButton as piano keys. What UIControlEvents should I listen for to get callbacks when button gets and loses highlighted state?

I tried to make subclass of UIButton and add property observer for highlighted and it was working fine. However sometimes I need to set highlighted state manually from code and that really messes it up as there is no way to tell whether event was user or app initiated.

Do you think you will get any callback to even listen to `AllEvents` when modified highlighted state from code? — zc246, Jan 12 '16 at 13:25
If I understand your problem right I think you should use UIControlEventTouchUpInside and UIControlEventTouchUpOutside event — Martin Makarsky, Jan 12 '16 at 13:29
Maybe use a `boolean` as an on/off toggle to keep track of the state... — l'L'l, Jan 12 '16 at 13:33

score 20 · Accepted Answer · edited Mar 01 '18 at 01:25

20

To mimic piano key behavior I used the following UIControlEvents:

self.addTarget(self, action: "pressed", forControlEvents: [.touchDown])
self.addTarget(self, action: "released", forControlEvents: [.touchDragExit, .touchUpInside, .touchUpOutside, .touchCancel])

edited Mar 01 '18 at 01:25

Richard Topchii

7,075
8
48
115

answered Jan 16 '16 at 14:37

Kirsteins

27,065
8
76
78

2

You may also want `touchDragEnter` to trigger `pressed` – Andrew Hershberger Sep 14 '18 at 16:52
You also probably don't need `touchUpOutside` since it necessarily happens after `touchDragExit` – Andrew Hershberger Sep 14 '18 at 16:56

score 2 · Answer 2 · answered Jan 12 '16 at 15:46

2

gets highlighted state:UIControlEventTouchDown

lose highlighted state:UIControlEventTouchDragOutside

answered Jan 12 '16 at 15:46

jiangjiefs

149
11

What control events start and end highlight state of UIButton

2 Answers2

Linked