objective-c - How does uipickerView get the method to start scrolling?

Question

My needs are as follows:
Address selector, if the province slides very fast, then click the OK button. A certain province - Beijing city - Dongcheng District
appeared. So what I want is to get the start and end scrolling method of uipickerView to limit the OK button.
I don’t know if there is a better way. Ask God for answers. Thank you