CODEWITHSUNDEEP
iosobjective-ctouch
George
George

Reputation: 949

iOS touchesMoved delay between first and second calls

I have some problems in my iOS app.

I have checked timestamps in the touchesMoved with clock() function and use difference between current and previous values. Difference between 1st and 2nd events is greater than others.

Have you any ideas?

Upvotes: 0

Views: 675

Answers (1)

ipmcc
ipmcc

Reputation: 29886

iOS is not a hard-realtime OS. There is generally no expectation that touch events will be delivered with regular frequency/uniform periods. You should not structure your app to depend on that. Events are delivered via the main thread, which could be delayed by other processing (drawing, etc.)

EDIT: If you're seeing huge differences in periods between the 1st and 2nd touches (relative to the periods between subsequent touch events), the first step would be to run the app in Instruments' Profiler template to see if some work that you're doing on the main thread in response to the first touch is causing the delay. If the delay is of your own doing, then fixing that is the first order of business.

Beyond that, you could try using various signal processing approaches to re-sample your data into uniform periodic data, but the problem is that any of those algorithms won't be able to deliver the first re-quantized point until at LEAST the 2nd (and more likely the 3rd or even later) event comes in, so if the principal problem is "The 2nd event doesn't come as soon as you'd like", then this won't help you.

Another good test: Try making an empty single-view sample app that does nothing but log the events as they come in -- if you see the same "odd" delay between 1st and 2nd touches in that trivial sample app, then that's just "how it is," and you can stop wasting time trying to change the OS behavior and move on to some different approach/solution.

Upvotes: 2

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