表头图片覆盖状态栏，这样状态栏的背景白色条就不会太难看

//表头

    self.tableView.tableHeaderView =[[UIView alloc]initWithFrame:CGRectMake(0, -20, SCREEN_WIDTH, 180)];

    self.tableView.tableHeaderView.backgroundColor = [UIColor orangeColor];

    UIImageView*imageV = [[UIImageView alloc]initWithFrame:CGRectMake(0, -20, SCREEN_WIDTH, 200)];

    imageV.image = [UIImage imageNamed:@"portalbg.png"];

    [self.tableView.tableHeaderView addSubview:imageV];

    self.tableView.scrollEnabled = YES;