UISearchBar 改变背景色

    UIView *backView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, _searchBar.size.width, _searchBar.size.height)];

    [backView setBackgroundColor:[UIColor colorWithRed:248/255.0 green:248/255.0 blue:248/255.0 alpha:1]];

    [_searchBar insertSubview:backView atIndex:1];