self.searchController = [[UISearchController alloc] initWithSearchResultsController:nil];
UISearchController.barTintColor = DEFAULT_BGCOLOR; // 设置背景颜色
self.searchController.dimsBackgroundDuringPresentation = NO; 开始搜索时背景是否显示
self.searchController.hidesNavigationBarDuringPresentation = YES; 搜索时，是否隐藏导航栏
self.searchController.searchResultsUpdater = self;设置搜索更新时调用的代理
self.searchController.searchBar.placeholder = @"请搜索人名";
self.searchController.searchBar.searchBarStyle = UISearchBarStyleProminent;
自定义搜索框的颜色 加上下面的话，就可以避免使用iOS8系统obscuresBackgroundDuringPresentation属性引起的崩溃问题
UIImageView *barImageView = [[[self.searchController.searchBar.subviews firstObject] subviews] firstObject];
barImageView.layer.borderColor = RGBCOLOR(238, 238, 238).CGColor; // 设置边框颜色
barImageView.layer.borderWidth = 1; 设置边框大小
self.searchController.searchBar.tintColor = kCommonColor; // 设置取消按钮的颜色
[self.searchController.searchBar sizeToFit]; 设置搜索框,自适应，否则搜索框无法显示
[lineView addSubview:self.searchController.searchBar];