Is it possible to use AutoLayout with UITableView's tableHeaderView?

Question

Since I discovered AutoLayout I use it everywhere, now I\'m trying to use it with a tableHeaderView.

I made a subclass of

Answer 1

I have figured out a workaround. wrap your autolayout wrriten xib header view in an empty uiview wrapper, and assign the header view to tableView's tableViewHeader property.

    UIView *headerWrapper = [[UIView alloc] init];
    AXLHomeDriverHeaderView *headerView = [AXLHomeDriverHeaderView loadViewFromNib];
    [headerWrapper addSubview:headerView];
    [headerView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(headerWrapper);
    }];
    self.tableView.tableHeaderView = headerView;

Answer 2

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
        header.setNeedsLayout()
        header.layoutIfNeeded()
        header.frame.size = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize)
        self.tableHeaderView = header
    }
}

Usage:

let header = SCAMessageView()
header.titleLabel.text = "Warning"
header.subtitleLabel.text = "Warning message here."
tableView.setAndLayoutTableHeaderView(header)

Answer 3

Updated for Swift 4.2

extension UITableView {

    var autolayoutTableViewHeader: UIView? {
        set {
            self.tableHeaderView = newValue
            guard let header = newValue else { return }
            header.setNeedsLayout()
            header.layoutIfNeeded()
            header.frame.size = 
            header.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize)
            self.tableHeaderView = header
        }
        get {
            return self.tableHeaderView
        }
    }
}

Answer 4

You can get autolayout to provide you with a size by using the systemLayoutSizeFittingSize method.

You can then use this to create the frame for your application. This technique works whenever you need to know the size of a view that uses autolayout internally.

The code in swift looks like

//Create the view
let tableHeaderView = CustomTableHeaderView()

//Set the content
tableHeaderView.textLabel.text = @"Hello world"

//Ask auto layout for the smallest size that fits my constraints    
let size = tableHeaderView.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize)

//Create a frame    
tableHeaderView.frame = CGRect(origin: CGPoint.zeroPoint, size: size)

//Set the view as the header    
self.tableView.tableHeaderView = self.tableHeaderView

Or in Objective-C

//Create the view
CustomTableHeaderView *header = [[CustomTableHeaderView alloc] initWithFrame:CGRectZero];

//Set the content
header.textLabel.text = @"Hello world";

//Ask auto layout for the smallest size that fits my constraints
CGSize size = [header systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];

//Create a frame
header.frame = CGRectMake(0,0,size.width,size.height);

//Set the view as the header  
self.tableView.tableHeaderView = header

It should also be noted that in this particular instance, overriding requiresConstraintBasedLayout in your subclass, does result in a layout pass being performed, however the results of this layout pass are ignored and the system frame set to the width of the tableView and 0 height.

Answer 5

Another solution is to dispatch the header view creation to the next main thread call:

- (void)viewDidLoad {
    [super viewDidLoad];

    // ....

    dispatch_async(dispatch_get_main_queue(), ^{
        _profileView = [[MyView alloc] initWithNib:@"MyView.xib"];
        self.tableView.tableHeaderView = self.profileView;
    });
}

Note: It fix the bug when the loaded view has a fixed height. I haven't tried when the header height only depends on its content.

EDIT :

You can find a cleaner solution to this problem by implementing this function, and calling it in viewDidLayoutSubviews

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    [self sizeHeaderToFit];
}

Answer 6

Here is how you can do in your UIViewController

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    if headerView.frame.size.height == 0 {
      headerView.label.preferredMaxLayoutWidth = view.bounds.size.width - 20
      let height = headerView.systemLayoutSizeFitting(UILayoutFittingCompressedSize).height

      headerView.frame.size = CGSize(width: tableView.bounds.size.width, height: height)
    }
  }