Using becomeFirstResponder causes cancel button to not work

问题

I have a UISearchDisplayController (searchDisplayCtr) and a UISearchBar (searchBar). I am trying to give focus to the search bar and bring up the keyboard when I click the search icon in the alphabet scroll on the right. If I include,

[self.searchDisplayCtr setActive:YES];
[self.searchDisplayCtr.searchBar becomeFirstResponder];

It brings up the keyboard and selects the search bar but the cancel button does not work consistently. I have tried resigning first responder, setting active to NO and both in searchDisplayControllerWillEndSearch, but it doesn't help. The cancel button will work only if no other letters on the alphabet scroll have been clicked yet.

回答1:

It is apparently necessary to scroll up to the top of the table before setting first responder. The code ended up being

[tableView setContentOffset:CGPointMake(0, 0) animated:NO];
[self.searchBar  becomeFirstResponder];

来源：https://stackoverflow.com/questions/21007059/using-becomefirstresponder-causes-cancel-button-to-not-work