iOS UISearchBar改变搜索框的颜色

//搜索框
- (UISearchBar *)searchBar{
    if (_searchBar == nil) {
        _searchBar = [[UISearchBar alloc]initWithFrame:CGRectMake(0, 27, KScreenWidth, 30)];
        _searchBar.placeholder = @"请输入搜索内容";
        _searchBar.backgroundImage = [[UIImage alloc] init];
        _searchBar.delegate = self;
        _searchBar.tintColor =  LHColor(196, 196, 196);
        //取出textfield
        
        UITextField *searchField=[_searchBar valueForKey:@"_searchField"];
        
//        searchField.backgroundColor = [UIColor grayColor];
//        searchField.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageWithContentsOfFile:@"ic_map_topbar_search"]];
//        searchField.background = [UIImage imageNamed:@"ic_map_topbar_search"];
        //改变searcher的textcolor
        searchField.borderStyle = UITextBorderStyleNone;
//        searchField.background = [UIImage imageNamed:@"ic_top"];
        searchField.backgroundColor = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.3];
        searchField.layer.cornerRadius = 4.0;
        searchField.leftViewMode=UITextFieldViewModeNever;
        searchField.textColor=[UIColor whiteColor];
        //改变placeholder的颜色
        
        [searchField setValue:[UIColor whiteColor]forKeyPath:@"_placeholderLabel.textColor"];
    }
    return _searchBar;
}