On Jan 22, 2017, at 18:27 , Eric Dolecki <[email protected]> wrote: > > Does anyone have a control (knob) that you can turn with a horizontal swipe, > but snaps to detents. It doesn't travel 360 degrees, but you can throw it and > it rubber bands at its minimum or maximum detent values. I can't seem to get > my head around getting all of it and I'm frustrated. An example range would > be 0-15 with 8 degrees between each detent value. So throw, slow turning, > both with snapping to avoid value (always an Int). > The knob will be quite large so the snapping will make sense.
The snapping behavior seems like an independent problem — once you’ve decided where the continuous motion would end, you can apply the snapping decision. The throwing part probably requires knowing the acceleration of the finger movement, and I don’t think there’s any existing API that will give this to you. You would have to track the touches as reported to you over time, using the positional differences to estimate a velocity, and using velocity differences to estimate an acceleration, and then apply a heuristic to decide whether an acceleration exceeds a threshold for recognition as a “throw”. However, given that your range of values is small (the table-view throwing has to deal with both short and long tables), you might be able to get away with a UIPanGestureRecognizer, if you aren’t going to require circular motion of the touches. It reports the velocity of the gesture, and you could try using a velocity threshold instead of an acceleration threshold — a fast movement throws to the extreme values, a slower movement tracks the finger — perhaps in conjunction with a minimum distance requirement. Circular rubber banding is likely something you’re going to have to invent for yourself. You’re probably going to have to look up a formula for spring dampening to get it to look natural, and implement a custom animation timing curve. _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
