UISearchController自动弹出键盘，调用becomeFirstResponder变为第一响应事件

_searchCtrl.searchResultsUpdater = self;
_searchCtrl.delegate = self; //有三个代理这要是这个代理没设置，坑死了
_searchCtrl.searchBar.delegate = self;

-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
self.searchCtrl.active = true;  //把active设为yes
}

- (void)didPresentSearchController:(UISearchController *)searchController
{
  dispatch_async(dispatch_get_main_queue(), ^{
        [self.searchCtrl.searchBar becomeFirstResponder]; //放主线程执行这个
    });
}