自定义UISearchBar

UISearchBar *searchBar = [[UISearchBar alloc]initWithFrame:_topView.bounds];
searchBar.placeholder = @"请输入您要搜索的商品";

-(void)searchBarTextDidBeginEditing:(UISearchBar *)searchBar{
    searchBar.showsCancelButton = YES;
    for(UIView *view in  [[[searchBar subviews] objectAtIndex:0] subviews]) {
        if([view isKindOfClass:[NSClassFromString(@"UINavigationButton") class]]) {
            UIButton * cancel =(UIButton *)view;
            [cancel setTitle:@"取消" forState:UIControlStateNormal];
            [cancel setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
            cancel.titleLabel.font = [UIFont systemFontOfSize:14];
        }
    }
}

UIView *backView = [[UIView alloc]initWithFrame:searchBar.bounds];
backView.backgroundColor = [UIColor colorWithRed:37/255.0 green:205/255.0 blue:120/255.0 alpha:1];
[searchBar insertSubview:backView atIndex:1];

UITextField *searchField = [searchBar valueForKey:@"_searchField"];
searchField.backgroundColor = [UIColor colorWithWhite:0.0 alpha:0.1];
searchField.clearButtonMode = UITextFieldViewModeNever;

UITextField *searchField = [searchBar valueForKey:@"_searchField"];
searchField.textColor = [UIColor whiteColor];
[searchField setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];

UITextField *searchField = [searchBar valueForKey:@"_searchField"];
UIImageView *iconView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"icon_search"]];
iconView.frame = CGRectMake(0, 0, 15 , 15);
searchField.leftView = iconView;