is there a uipickerview delegate method like scrollviewDidScroll?

Question

I have a customized UIPickerview and I do not want to use a datepicker. I want to implement the feature where when a user scrolls down/up the hours, the AM/PM component swi

Answer 1

Unfortunately, the above solutions (setting a flag when data source methods such as titleForRow are called and resetting it when didSelectRow is called) are sketchy and won't work in many cases. The data source methods may be called in many cases where there is no scrolling by the user - such as UI changes resulting in changing view layouts, and also may be called immediately after didSelectRow - you have no control over when these methods are called.

In relation to this particular question, these solutions may work, since these methods are always called when scrolling - just not ONLY when scrolling. However, care needs to be taken not to assume that the user MUST be scrolling in these cases. Also, if you manage a state machine with this flag (like disabling some button when scrolling and enabling it after), you'll get in trouble.

Finally, this only allows detecting a scroll (with the above caveats), but it won't tell you the speed or current values - so it would be difficult to tell when to switch the AM/PM label.

The only way I was able to reliably detect a scroll was through a mess of flags that I set when UI changes are made and other ugly hacks (like waiting 100 ms after a didSelectRow before trying to detect scrolls again, because I noticed calls to the data source immediately after didSelectRow). Adding willScroll/didScroll methods to the delegate seems like an obvious thing Apple neglected to add.