self.definesPresentationContext = YES;
-----
_searchController = [[UISearchController alloc]initWithSearchResultsController:nil];
_searchController.dimsBackgroundDuringPresentation = NO;
_searchController . hidesNavigationBarDuringPresentation = NO;
_searchController.searchBar.frame = CGRectMake(self.searchController.searchBar.frame.origin.x, self.searchController.searchBar.frame.origin.y, self.searchController.searchBar.frame.size.width, 44.0);
_searchController.searchBar.placeholder=@"搜索店铺地址";
_searchController.searchBar.returnKeyType = UIReturnKeySearch;
_searchController.searchBar.delegate = self;;
_tbvw.tableHeaderView = self.searchController.searchBar;
self.definesPresentationContext = YES;