为什么tableVieW:viewForHeaderInSection忽略UILabel的框架属性?

Basically I want to change the font and the color of my section header, so I implement tableVieW:viewForHeaderInSection. First I tried this code:

基本上，我想要改变section header的字体和颜色，所以我实现了tableVieW:viewForHeaderInSection。首先，我尝试了以下代码:

-(UIView *) tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    UILabel* headerLabel = [[[UILabel alloc] init] autorelease];
    headerLabel.frame = CGRectMake(10, 0, 300, 40);
    headerLabel.backgroundColor = [UIColor clearColor];
    headerLabel.textColor = [UIColor blackColor];
    headerLabel.font = [UIFont boldSystemFontOfSize:18];
    headerLabel.text = @"My section header";

    return headerLabel;
}

but for some reason the frame property is ignored (I'm talking about the 10px inset on the left). Now I use the following:

但是由于某种原因，frame属性被忽略(我说的是左边的10px inset)。现在我使用以下方法:

-(UIView *) tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    UIView* headerView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 40)] autorelease];

    UILabel* headerLabel = [[UILabel alloc] init];
    headerLabel.frame = CGRectMake(10, 0, 300, 40);
    headerLabel.backgroundColor = [UIColor clearColor];
    headerLabel.textColor = [UIColor blackColor];
    headerLabel.font = [UIFont boldSystemFontOfSize:18];
    headerLabel.text = @"My section header";

    [headerView addSubview:headerLabel];
    [headerLabel release];

    return headerView;
}

with the desired results. Can someone explain to me why the second approach works and the first doesn't?

与预期的结果。有人能解释一下为什么第二种方法有效，而第一种方法无效吗?

PS. In both cases I implement tableView:heightForHeaderInSection as well, returning 40.0

在这两种情况下，我都实现了tableView:heightForHeaderInSection，返回40.0。

2 个解决方案

#1

That's because the UITableView automatically sets the frame of the header view you provide to

这是因为UITableView会自动设置你提供给头视图的框架

(0, y, table view width, header view height)

(0, y，表视图宽度，页眉视图高度)

y is the computed position of the view and header view height is the value returned by tableView:heightForHeaderInSection:

y是视图的计算位置，头视图高度是tableView返回的值:heightForHeaderInSection:

#2

Maybe it's better do add a subview:

也许最好添加一个子视图:

func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
    let view = UIView(frame: CGRect(x: 0, y: 0, width: 20, height: 20))
    let label = UILabel(frame: CGRect(x: 15, y: 5, width: tableView.frame.width, height: 20))
    label.text = "\(sections[section].year)"
    view.addSubview(label)
    return view
}

#1