Table Header View Height Is Wrong When Using Auto Layout, Ib, and Font Sizes

UITableView: Set table header view height based on screen size

Unfortunately, table header views cannot be sized using auto layout. You can use auto layout for elements inside the header but you have to specify the header's size by explicitly setting its frame. If the header's height is static and known at compile time you can use IB. However, if the height is dynamic or depends on the device (as in your case), you have to set it in code.

A quite flexible solution would be to create a custom subclass of UITableView and adapt the header's frame in the layoutSubviews method. This way the header's size gets automatically adjusted when the table view is resized. You have to be careful, however, to only re-apply the header's frame when a change is actually needed to avoid an infinite loop.

Here's what it would look like in Objective-C:

@interface MyTableView : UITableView
@end

@implementation MyTableView : UITableView

- (void)layoutSubviews {
    [super layoutSubviews];

    if (self.tableHeaderView) {
        UIView *header = self.tableHeaderView;
        CGRect rect = CGRectMake(0, 0, self.bounds.size.width,
                                 self.bounds.size.height / 2);

        // Only adjust frame if needed to avoid infinite loop
        if (!CGRectEqualToRect(self.tableHeaderView.frame, rect)) {
            header.frame = rect;

            // This will apply the new header size and trigger another
            // call of layoutSubviews
            self.tableHeaderView = header;
        }
    }
}

@end

The Swift version looks like this:

class MyTableView: UITableView {

    override func layoutSubviews() {
        super.layoutSubviews()

        if let header = tableHeaderView {
            let rect = CGRectMake(0, 0, bounds.size.width, bounds.size.height / 2)

            // Only adjust frame if needed to avoid infinite loop
            if !CGRectEqualToRect(header.frame, rect) {
                header.frame = rect

                // This will apply the new header size and trigger 
                // another call of layoutSubviews
                tableHeaderView = header
            }
        }
    }

}

Note that the above snippets use the bounds of the table view rather than the screen size to calculate the header size.

Update: Note that sometimes an additional call to layoutIfNeeded is needed after setting the tableHeaderView property. I ran into an issue where section headers were drawn above the header view without calling layoutIfNeeded.

tableHeaderView with Autolayout not working correctly

In order to make it work you'll need some magic or migrate away from table header view. I've already answered on a similar question here. The trick is to magically reset tableHeaderView after evaluating it's height via autolayout. I've created sample project for that: TableHeaderView+Autolayout.

Strange behavior when setting height of a table header view

When using auto layout, iOS will keep a 600 * 600 screen size until func viewDidLayoutSubviews() is called. Hence you should do your dynamic adjustment of layouts in viewDidLayoutSubviews() rather than viewDidLoad().

I put the print(tableHeader.frame.size) in viewDidLayoutSubviews() as well and the result is (374.0, 501.0). And when I adjust header height in this function it all turned out correct.

How do I set the height of tableHeaderView (UITableView) with autolayout?

You need to use the UIView systemLayoutSizeFittingSize: method to obtain the minimum bounding size of your header view.

I provide further discussion on using this API in this Q/A:

How to resize superview to fit all subviews with autolayout?

Using autolayout in a tableHeaderView

My own best answer so far involves setting the tableHeaderView once and forcing a layout pass. This allows a required size to be measured, which I then use to set the frame of the header. And, as is common with tableHeaderViews, I have to again set it a second time to apply 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;
}

For multiline labels, this also relies on the custom view (the message view in this case) setting the preferredMaxLayoutWidth of each:

- (void)layoutSubviews
{
    [super layoutSubviews];

    self.titleLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.titleLabel.frame);
    self.subtitleLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.subtitleLabel.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()
let height = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
var frame = header.frame
frame.size.height = height
header.frame = frame
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()
        let height = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
        var frame = header.frame
        frame.size.height = height
        header.frame = frame
        self.tableHeaderView = header
    }
}

Usage:

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

Sizing of table view cell and table view header view

Your custom cell "starts with" a ContentView, which uses uses the table view's insets to set its width...

So, if you have a bunch of elements / objects that you are adding to the content view...

Your best bet is to probably first add a standard UIView as a "container view"... (just my naming of it)...

Then, set the constraints on that "containing view" to be 0.9 of the width of the contentView...

All of the elements you add to that "containing view" will be constrained relative to it and thus will all stay inside the 0.9-width overall...

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

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)

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