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


Answers

I really battled with this one and plonking the setup into viewDidLoad didn't work for me since the frame is not set in viewDidLoad, I also ended up with tons of messy warnings where the encapsulated auto layout height of the header was being reduced to 0. I only noticed the issue on iPad when presenting a tableView in a Form presentation.

What solved the issue for me was setting the tableViewHeader in viewWillLayoutSubviews rather than in viewDidLoad.

func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        if tableView.tableViewHeaderView == nil {
            let header: MyHeaderView = MyHeaderView.createHeaderView()
            header.setNeedsUpdateConstraints()
            header.updateConstraintsIfNeeded()
            header.frame = CGRectMake(0, 0, CGRectGetWidth(tableView.bounds), CGFloat.max)
            var newFrame = header.frame
            header.setNeedsLayout()
            header.layoutIfNeeded()
            let newSize = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize)
            newFrame.size.height = newSize.height
            header.frame = newFrame
            self.tableView.tableHeaderView = header
        }
    }
Question

I'm been smashing my head against the wall with this for last 3 or 4 hours and I can't seem to figure it out. I have a UIViewController with a full screen UITableView inside of it (there's some other stuff on the screen, which is why I can't use a UITableViewController) and I want to get my tableHeaderView to resize with autolayout. Needless to say, it's not cooperating.

See screenshot below.

Because the overviewLabel (e.g. the "List overview information here." text) has dynamic content, I'm using autolayout to resize it and it's superview. I've got everything resizing nicely, except for the tableHeaderView, which is right below Paralax Table View in the hiearchy.

The only way I've found to resize that header view is programatically, with the following code:

CGRect headerFrame = self.headerView.frame;
headerFrame.size.height = headerFrameHeight;
self.headerView.frame = headerFrame;
[self.listTableView setTableHeaderView:self.headerView];

In this case, headerFrameHeight is a manual calculation of the tableViewHeader height as follows (innerHeaderView is the white area, or the second "View", headerView is tableHeaderView):

CGFloat startingY = self.innerHeaderView.frame.origin.y + self.overviewLabel.frame.origin.y;
CGRect overviewSize = [self.overviewLabel.text
                       boundingRectWithSize:CGSizeMake(290.f, CGFLOAT_MAX)
                       options:NSStringDrawingUsesLineFragmentOrigin
                       attributes:@{NSFontAttributeName: self.overviewLabel.font}
                       context:nil];
CGFloat overviewHeight = overviewSize.size.height;
CGFloat overviewPadding = ([self.overviewLabel.text length] > 0) ? 10 : 0; // If there's no overviewText, eliminate the padding in the overall height.
CGFloat headerFrameHeight = ceilf(startingY + overviewHeight + overviewPadding + 21.f + 10.f);

The manual calculation works, but it's clunky and prone to error if things change in the future. What I want to be able to do is have the tableHeaderView auto-resize based on the provided constraints, like you can anywhere else. But for the life of me, I can't figure it out.

There's several posts on SO about this, but none are clear and ended up confusing me more. Here's a few:

It doesn't really make sense to change the translatesAutoresizingMaskIntoConstraints property to NO, since that just causes errors for me and doesn't make sense conceptually anyway.

Any help would really be appreciated!

EDIT 1: Thanks to TomSwift's suggestion, I was able to figure it out. Instead of manually calculating the height of the overview, I can have it calculated for me as follows and then re-set the tableHeaderView as before.

[self.headerView setNeedsLayout];
[self.headerView layoutIfNeeded];
CGFloat height = [self.innerHeaderView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height + self.innerHeaderView.frame.origin.y; // adding the origin because innerHeaderView starts partway down headerView.

CGRect headerFrame = self.headerView.frame;
headerFrame.size.height = height;
self.headerView.frame = headerFrame;
[self.listTableView setTableHeaderView:self.headerView];

Edit 2: As others have noted, the solution posted in Edit 1 doesn't seem to work in viewDidLoad. It does, however, seem to work in viewWillLayoutSubviews. Example code below:

// Note 1: The variable names below don't match the variables above - this is intended to be a simplified "final" answer.
// Note 2: _headerView was previously assigned to tableViewHeader (in loadView in my case since I now do everything programatically).
// Note 3: autoLayout code can be setup programatically in updateViewConstraints.
- (void)viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];

    [_headerWrapper setNeedsLayout];
    [_headerWrapper layoutIfNeeded];
    CGFloat height = [_headerWrapper systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

    CGRect headerFrame = _headerWrapper.frame;
    headerFrame.size.height = height;
    _headerWrapper.frame = headerFrame;
    _tableView.tableHeaderView = _headerWrapper;
}



It is quite possible to use generic AutoLayout-based UIView with any AL inner subview structure as a tableHeaderView.

The only thing one needs is to set a simple tableFooterView before!

Let self.headerView is some constraint-based UIView.

- (void)viewDidLoad {

    ........................

    self.tableView.tableFooterView = [UIView new];

    [self.headerView layoutIfNeeded]; // to set initial size

    self.tableView.tableHeaderView = self.headerView;

    [self.tableView.leadingAnchor constraintEqualToAnchor:self.headerView.leadingAnchor].active = YES;
    [self.tableView.trailingAnchor constraintEqualToAnchor:self.headerView.trailingAnchor].active = YES;
    [self.tableView.topAnchor constraintEqualToAnchor:self.headerView.topAnchor].active = YES;

    // and the key constraint
    [self.tableFooterView.trailingAnchor constraintEqualToAnchor:self.headerView.trailingAnchor].active = YES;
}

If self.headerView changes height under UI rotation one have to implement

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

    [coordinator animateAlongsideTransition: ^(id<UIViewControllerTransitionCoordinatorContext> context) {
        // needed to resize header height
        self.tableView.tableHeaderView = self.headerView;
    } completion: NULL];
}

One can use ObjC category for this purpose

@interface UITableView (AMHeaderView)
- (void)am_insertHeaderView:(UIView *)headerView;
@end

@implementation UITableView (AMHeaderView)

- (void)am_insertHeaderView:(UIView *)headerView {

    NSAssert(self.tableFooterView, @"Need to define tableFooterView first!");

    [headerView layoutIfNeeded];

    self.tableHeaderView = headerView;

    [self.leadingAnchor constraintEqualToAnchor:headerView.leadingAnchor].active = YES;
    [self.trailingAnchor constraintEqualToAnchor:headerView.trailingAnchor].active = YES;
    [self.topAnchor constraintEqualToAnchor:headerView.topAnchor].active = YES;

    [self.tableFooterView.trailingAnchor constraintEqualToAnchor:headerView.trailingAnchor].active = YES;
}
@end

And also Swift extension

extension UITableView {

    func am_insertHeaderView2(_ headerView: UIView) {

        assert(tableFooterView != nil, "Need to define tableFooterView first!")

        headerView.layoutIfNeeded()

        tableHeaderView = headerView

        leadingAnchor.constraint(equalTo: headerView.leadingAnchor).isActive = true
        trailingAnchor.constraint(equalTo: headerView.trailingAnchor).isActive = true
        topAnchor.constraint(equalTo: headerView.topAnchor).isActive = true

        tableFooterView?.trailingAnchor.constraint(equalTo: headerView.trailingAnchor).isActive = true
    }
}



This solution resizes the tableHeaderView and avoids infinite loop in the viewDidLayoutSubviews() method I was having with some of the other answers here:

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    if let headerView = tableView.tableHeaderView {
        let height = headerView.systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
        var headerFrame = headerView.frame

        // comparison necessary to avoid infinite loop
        if height != headerFrame.size.height {
            headerFrame.size.height = height
            headerView.frame = headerFrame
            tableView.tableHeaderView = headerView
        }
    }
}

See also this post: https://.com/a/34689293/1245231




Your solution using systemLayoutSizeFittingSize: works if the header view is just updated once on each view appearance. In my case, the header view updated multiple times to reflect status changes. But systemLayoutSizeFittingSize: always reported the same size. That is, the size corresponding to the first update.

To get systemLayoutSizeFittingSize: to return the correct size after each update I had to first remove the table header view before updating it and re-adding it:

self.listTableView.tableHeaderView = nil;
[self.headerView removeFromSuperview];