I asked and answered a similar question here. In summary, I add the header once and use it to find the required height. That height can then be applied to the header, and the header is set a second time to reflect the change.
- (void)viewDidLoad
{
[super viewDidLoad];
self.header = [[SCAMessageView alloc] init];
self.header.titleLabel.text = @"Warning";
self.header.subtitleLabel.text = @"This is a message with enough text to span multiple lines. This text is set at runtime and might be short or long.";
//set the tableHeaderView so that the required height can be determined
self.tableView.tableHeaderView = self.header;
[self.header setNeedsLayout];
[self.header layoutIfNeeded];
CGFloat height = [self.header systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
//update the header's frame and set it again
CGRect headerFrame = self.header.frame;
headerFrame.size.height = height;
self.header.frame = headerFrame;
self.tableView.tableHeaderView = self.header;
}
If you have multi-line labels, this also relies on the custom view setting the preferredMaxLayoutWidth of each label:
- (void)layoutSubviews
{
[super layoutSubviews];
self.titleLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.titleLabel.frame);
self.subtitleLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.subtitleLabel.frame);
}
or perhaps more generally:
override func layoutSubviews() {
super.layoutSubviews()
for view in subviews {
guard let label = view as? UILabel where label.numberOfLines == 0 else { continue }
label.preferredMaxLayoutWidth = CGRectGetWidth(label.frame)
}
}
Update January 2015
Unfortunately this still seems necessary. Here is a swift version of the layout process:
tableView.tableHeaderView = header
header.setNeedsLayout()
header.layoutIfNeeded()
header.frame.size = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize)
tableView.tableHeaderView = header
I’ve found it useful to move this into an extension on UITableView:
extension UITableView {
//set the tableHeaderView so that the required height can be determined, update the header's frame and set it again
func setAndLayoutTableHeaderView(header: UIView) {
self.tableHeaderView = header
self.tableHeaderView?.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
header.widthAnchor.constraint(equalTo: self.widthAnchor)
])
header.setNeedsLayout()
header.layoutIfNeeded()
header.frame.size = header.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize)
self.tableHeaderView = header
}
}
Usage:
let header = SCAMessageView()
header.titleLabel.text = "Warning"
header.subtitleLabel.text = "Warning message here."
tableView.setAndLayoutTableHeaderView(header)