添加textField到tableviewheader

需要给标题视图添加一个textField，但是不知道为什么代码执行之后无法看见textField。在使用label的时候正常。

代码：

-(UIView*) tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section{
       UIView *tableHeaderView = [[UIView alloc] initWithFrame:CGRectMake(40, 0, self.view.frame.size.width - 70, 30)];
    UITextField *sectionTitleTF1 = [[UITextField alloc] initWithFrame:CGRectMake(58, 0, 500, 30)];
    sectionTitleTF1.backgroundColor = [UIColor whiteColor];
    [sectionTitleTF1 becomeFirstResponder];
    [tableHeaderView addSubview:sectionTitleTF1];
return tableHeaderView;
}

 - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section{
return 30.0;
}

    -(UIView*) tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section{
    UIView *tableHeaderView = [[UIView alloc] initWithFrame:CGRectMake(40, 0, self.view.frame.size.width - 70, 30)];
    tableHeaderView.backgroundColor =[UIColor grayColor];
    UITextField *sectionTitleTF1 = [[UITextField alloc] initWithFrame:CGRectMake(58, 0, 500, 30)];
    sectionTitleTF1.backgroundColor = [UIColor whiteColor];
    [sectionTitleTF1 setBackgroundColor:[UIColor whiteColor]];
    [sectionTitleTF1 setFont:[UIFont boldSystemFontOfSize:15]];
    [sectionTitleTF1 setBorderStyle:UITextBorderStyleLine];
    [sectionTitleTF1 setTextAlignment:UITextAlignmentCenter];
    [sectionTitleTF1 setKeyboardType:UIKeyboardTypeNumbersAndPunctuation];
    [sectionTitleTF1 becomeFirstResponder];
    [tableHeaderView addSubview:sectionTitleTF1];
    return tableHeaderView;
    }