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


Answers

I've been unable to add a header view using constraints (in code). If I give my view a width and/or a height constraint, I get a crash with the message saying:

 "terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Auto Layout still required after executing -layoutSubviews. UITableView's implementation of -layoutSubviews needs to call super."

When I add a view in the storyboard to my table view, it shows no constraints, and it works fine as a header view, so I think that the placement of the header view isn't done using constraints. It doesn't seem to behave like a normal view in that regard.

The width is automatically the width of the table view, the only thing you need to set is the height -- the origin values are ignored, so it doesn't matter what you put in for those. For instance, this worked fine (as does 0,0,0,80 for the rect):

UIView *headerview = [[UIView alloc] initWithFrame:CGRectMake(1000,1000, 0, 80)];
headerview.backgroundColor = [UIColor yellowColor];
self.tableView.tableHeaderView = headerview;
Question

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

I made a subclass of UIView added everything (labels etc...) I wanted with their constraints, then I added this CustomView to the UITableView'tableHeaderView.

Everything works just fine except the UITableView always displays above the CustomView, by above I mean the CustomView is under the UITableView so it can't be seen !

It seems that no matter what I do, the height of the UITableView'tableHeaderView is always 0 (so is the width, x and y).

My question : is it possible at all to accomplish this without setting the frame manually ?

EDIT : The CustomView'subview that I'm using has these constraints :

_title = [[UILabel alloc]init];
_title.text = @"Title";
[self addSubview:_title];
[_title keep:[KeepTopInset rules:@[[KeepEqual must:5]]]]; // title has to stay at least 5 away from the supperview Top
[_title keep:[KeepRightInset rules:@[[KeepMin must:5]]]];
[_title keep:[KeepLeftInset rules:@[[KeepMin must:5]]]];
[_title keep:[KeepBottomInset rules:@[[KeepMin must:5]]]];

I'm using a handy library 'KeepLayout' because writing constraints manually takes forever and way too many line for one single constraint but the methods are self-explaining.

And the UITableView has these constraints :

_tableView = [[UITableView alloc]init];
_tableView.translatesAutoresizingMaskIntoConstraints = NO;
_tableView.delegate = self;
_tableView.dataSource = self;
_tableView.backgroundColor = [UIColor clearColor];
[self.view addSubview:_tableView];
[_tableView keep:[KeepTopInset rules:@[[KeepEqual must:0]]]];// These 4 constraints make the UITableView stays 0 away from the superview top left right and bottom.
[_tableView keep:[KeepLeftInset rules:@[[KeepEqual must:0]]]];
[_tableView keep:[KeepRightInset rules:@[[KeepEqual must:0]]]];
[_tableView keep:[KeepBottomInset rules:@[[KeepEqual must:0]]]];

_detailsView = [[CustomView alloc]init];
_tableView.tableHeaderView = _detailsView;

I don't know if I have to set some constraints directly on the CustomView, I think the height of the CustomView is determined by the constraints on the UILabel "title" in it.

EDIT 2: After another investigation it seems the height and width of the CustomView are correctly calculated, but the top of the CustomView is still at the same level than the top of the UITableView and they move together when I scroll.




An old post. But a good post. Here's my 2 cents.

Firstly, ensure that your header view has its constraints arranged so that it can support it's own intrinsic content size. Then do the following.

//ViewDidLoad
headerView.translatesAutoresizingMaskIntoConstraints = false
headerView.configure(title: "Some Text A")

//Somewhere else
headerView.update(title: "Some Text B)

private var widthConstrained = false

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    if widthConstrained == false {
        widthConstrained = true
        tableView.addConstraint(NSLayoutConstraint(item: headerView, attribute: .width, relatedBy: .equal, toItem: tableView, attribute: .width, multiplier: 1, constant: 0))
        headerView.layoutIfNeeded()
        tableView.layoutIfNeeded()
    }
}

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)
    coordinator.animate(alongsideTransition: { (context) in
        self.headerView.layoutIfNeeded()
        self.tableView.layoutIfNeeded()
    }, completion: nil)
}



Share my approach.

UITableView+XXXAdditions.m

- (void)xxx_setTableHeaderView:(UIView *)tableHeaderView layoutBlock:(void(^)(__kindof UIView *tableHeaderView, CGFloat *containerViewHeight))layoutBlock {
      CGFloat containerViewHeight = 0;
      UIView *backgroundView = [[UIView alloc] initWithFrame:CGRectZero];
      [backgroundView addSubview:tableHeaderView];
      layoutBlock(tableHeaderView, &containerViewHeight);

      backgroundView.frame = CGRectMake(0, 0, 0, containerViewHeight);

      self.tableHeaderView = backgroundView;
}

Usage.

[self.tableView xxx_setTableHeaderView:myView layoutBlock:^(__kindof UIView * _Nonnull tableHeaderView, CGFloat *containerViewHeight) {
    *containerViewHeight = 170;

    [tableHeaderView mas_makeConstraints:^(MASConstraintMaker *make) {
      make.top.equalTo(@20);
      make.centerX.equalTo(@0);
      make.size.mas_equalTo(CGSizeMake(130, 130));
    }];
  }];



Accepted answer is a only useful for tables with a single section. For multi-section UITableView just make sure that your header inherits from UITableViewHeaderFooterView and you will be fine.

As an alternative, just embed your current header in the contentView of a UITableViewHeaderFooterView. Exactly like UITableViewCell works.




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];
}



Code:

  extension UITableView {

          func sizeHeaderToFit(preferredWidth: CGFloat) {
            guard let headerView = self.tableHeaderView else {
              return
            }

            headerView.translatesAutoresizingMaskIntoConstraints = false
            let layout = NSLayoutConstraint(
              item: headerView,
              attribute: .Width,
              relatedBy: .Equal,
              toItem: nil,
              attribute:
              .NotAnAttribute,
              multiplier: 1,
              constant: preferredWidth)

            headerView.addConstraint(layout)

            let height = headerView.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
            headerView.frame = CGRectMake(0, 0, preferredWidth, height)

            headerView.removeConstraint(layout)
            headerView.translatesAutoresizingMaskIntoConstraints = true

            self.tableHeaderView = headerView
          }
  }



My table header view is a UIView subclass - I created a single contentView UIView within the initializer, with its bounds the same as the table header view's frame and added all my objects as a subview of that.

Then add the constraints for your objects within the table header view's layoutSubviews method rather than within the initializer. That solved the crash.

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:CGRectMake(0, 0, 0, 44.0)];
    if (self) {
        UIView *contentView = [[UIView alloc] initWithFrame:self.bounds];
        contentView.autoresizingMask = UIViewAutoresizingFlexibleWidth;

        // add other objects as subviews of content view

    }
    return self;
}

- (void)layoutSubviews
{
    [super layoutSubviews];

    // remake constraints here
}



I know this is an old post but After going through all the SO posts regarding this and passing a whole afternoon playing with this, I finally came up with a clean and yet very simple solution

First of all, My view hierarchy looks like this:

  1. Table View
    1. View tableHeaderView
      1. View with an outlet called headerView

Now inside the View (No.3), I set up all the constraints as I would normally including the bottom space to container. This will make the container (i.e. 3.View i.e. headerView) to size itself based on it's subviews and their constraints.

After that, I set the constraints between 3. View and 2. View to these:

  1. Top Space to container: 0
  2. Leading Space to container: 0
  3. Trailing Space to container: 0

Notice that I omit intentionally the bottom space intentionally.

Once all of this is done in the storyboard, everything that's left to do is paste those three lines of codes:

if (self.headerView.frame.size.height != self.tableView.tableHeaderView.frame.size.height) {
    UIView *header = self.tableView.tableHeaderView;
    CGRect frame = self.tableView.tableHeaderView.frame;
    frame.size.height = self.headerView.frame.size.height + frame.origin.y;
    header.frame = frame;
    self.tableView.tableHeaderView = header;
}



Strange things happens. systemLayoutSizeFittingSize works great for iOS9, but doesn't for iOS 8 in my case. So this problems solves quite easy. Just get link to the bottom view in header and in viewDidLayoutSubviews after super call update header view bounds by inserting height as CGRectGetMaxY(yourview.frame) + padding

UPD: The easiest solution ever: So, in header view place subview and pin it to left, right, top. In that subview place your subviews with auto-height constraints. After that give all the job to the autolayout (no calculation required)

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    CGFloat height = CGRectGetMaxY(self.tableView.tableHeaderView.subviews.firstObject.frame);
    self.tableView.tableHeaderView.bounds = CGRectMake(0, 0, CGRectGetWidth(self.tableView.bounds), height);
    self.tableView.tableHeaderView = self.tableView.tableHeaderView;
}

As a result subview is expanding/shrinking like it should, at the end it calls viewDidLayoutSubviews. At the time we know the actual size of the view, so set headerView height and update it by re-assigning. Works like a charm!

Also works for footer view.




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)
    }
  }



My AutoLayout is working very good:

CGSize headerSize = [headerView systemLayoutSizeFittingSize:CGSizeMake(CGRectGetWidth([UIScreen mainScreen].bounds), 0) withHorizontalFittingPriority:UILayoutPriorityRequired verticalFittingPriority:UILayoutPriorityFittingSizeLevel];
headerView.frame = CGRectMake(0, 0, headerSize.width, headerSize.height);
self.tableView.tableHeaderView = headerView;



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