Building a titleView programmatically with constraints (or generally constructing a view with constraints)

I really needed constraints, so played around with it today. What I found that works is this:

    let v  = UIView()
    v.translatesAutoresizingMaskIntoConstraints = false
    // add your views and set up all the constraints

    // This is the magic sauce!
    v.layoutIfNeeded()
    v.sizeToFit()

    // Now the frame is set (you can print it out)
    v.translatesAutoresizingMaskIntoConstraints = true // make nav bar happy
    navigationItem.titleView = v

Works like a charm!


an0's answer is correct. However, it doesn't help you getting the desired effect.

Here's my recipe for building title views that automatically have the right size:

  • Create a UIView subclass, for instance CustomTitleView that will be later used as the navigationItem's titleView.
  • Use auto layout inside CustomTitleView. If you want to have your CustomTitleView being always centered, you'll need to add an explicit CenterX constraint (see code and link below).
  • Call updateCustomTitleView (see below) every time your titleView content updates. We need to set the titleView to nil and set it afterwards to our view again to prevent the title view being offset centered. This would happen when the title view changes from wide to narrow.
  • DON'T disable translatesAutoresizingMaskIntoConstraints

Gist: https://gist.github.com/bhr/78758bd0bd4549f1cd1c

Updating CustomTitleView from your ViewController:

- (void)updateCustomTitleView
{
    //we need to set the title view to nil and get always the right frame
    self.navigationItem.titleView = nil;

    //update properties of your custom title view, e.g. titleLabel
    self.navTitleView.titleLabel.text = <#my_property#>;

    CGSize size = [self.navTitleView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
    self.navTitleView.frame = CGRectMake(0.f, 0.f, size.width, size.height);

    self.navigationItem.titleView = self.customTitleView;
}

Sample CustomTitleView.h with one label and two buttons

#import <UIKit/UIKit.h>

@interface BHRCustomTitleView : UIView

@property (nonatomic, strong, readonly) UILabel *titleLabel;
@property (nonatomic, strong, readonly) UIButton *previousButton;
@property (nonatomic, strong, readonly) UIButton *nextButton;

@end

Sample CustomTitleView.m:

#import "BHRCustomTitleView.h"

@interface BHRCustomTitleView ()

@property (nonatomic, strong) UILabel *titleLabel;
@property (nonatomic, strong) UIButton *previousButton;
@property (nonatomic, strong) UIButton *nextButton;

@property (nonatomic, copy) NSArray *constraints;

@end

@implementation BHRCustomTitleView

- (void)updateConstraints
{
    if (self.constraints) {
        [self removeConstraints:self.constraints];
    }

    NSDictionary *viewsDict = @{ @"title": self.titleLabel,
                                 @"previous": self.previousButton,
                                 @"next": self.nextButton };
    NSMutableArray *constraints = [NSMutableArray array];

    [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(>=0)-[previous]-2-[title]-2-[next]-(>=0)-|"
                                                                             options:NSLayoutFormatAlignAllBaseline
                                                                             metrics:nil
                                                                               views:viewsDict]];

    [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[previous]|"
                                                                             options:0
                                                                             metrics:nil
                                                                               views:viewsDict]];

    [constraints addObject:[NSLayoutConstraint constraintWithItem:self
                                                        attribute:NSLayoutAttributeCenterX
                                                        relatedBy:NSLayoutRelationEqual
                                                           toItem:self.titleLabel
                                                        attribute:NSLayoutAttributeCenterX
                                                       multiplier:1.f
                                                         constant:0.f]];
    self.constraints = constraints;
    [self addConstraints:self.constraints];

    [super updateConstraints];
}

- (UILabel *)titleLabel
{
    if (!_titleLabel)
    {
        _titleLabel = [[UILabel alloc] initWithFrame:CGRectZero];
        _titleLabel.translatesAutoresizingMaskIntoConstraints = NO;
        _titleLabel.font = [UIFont boldSystemFontOfSize:_titleLabel.font.pointSize];

        [self addSubview:_titleLabel];
    }

    return _titleLabel;
}


- (UIButton *)previousButton
{
    if (!_previousButton)
    {
        _previousButton = [UIButton buttonWithType:UIButtonTypeSystem];
        _previousButton.translatesAutoresizingMaskIntoConstraints = NO;
        [self addSubview:_previousButton];

        _previousButton.titleLabel.font = [UIFont systemFontOfSize:23.f];
        [_previousButton setTitle:@"❮"
                         forState:UIControlStateNormal];
    }

    return _previousButton;
}

- (UIButton *)nextButton
{
    if (!_nextButton)
    {
        _nextButton = [UIButton buttonWithType:UIButtonTypeSystem];
        _nextButton.translatesAutoresizingMaskIntoConstraints = NO;
        [self addSubview:_nextButton];
        _nextButton.titleLabel.font = [UIFont systemFontOfSize:23.f];
        [_nextButton setTitle:@"❯"
                     forState:UIControlStateNormal];
    }

    return _nextButton;
}

+ (BOOL)requiresConstraintBasedLayout
{
    return YES;
}

@end

Thanks @Valentin Shergin and @tubtub! According to their answers I made an implementation of navigation bar title with dropdown arrow image in Swift 1.2:

  1. Create a UIView subclass for custom titleView
  2. In your subclass: a) Use auto layout for subviews but not for itself. Set translatesAutoresizingMaskIntoConstraints to false for subviews and true for titleView itself. b) Implement sizeThatFits(size: CGSize)
  3. If your title can change call titleLabel.sizeToFit() and self.setNeedsUpdateConstraints() inside titleView's subclass after text changes
  4. In your ViewController call custom updateTitleView() and make sure to call titleView.sizeToFit() and navigationBar.setNeedsLayout() in there

Here's minimal implementation of DropdownTitleView:

import UIKit

class DropdownTitleView: UIView {

    private var titleLabel: UILabel
    private var arrowImageView: UIImageView

    // MARK: - Life cycle

    override init (frame: CGRect) {

        self.titleLabel = UILabel(frame: CGRectZero)
        self.titleLabel.setTranslatesAutoresizingMaskIntoConstraints(false)

        self.arrowImageView = UIImageView(image: UIImage(named: "dropdown-arrow")!)
        self.arrowImageView.setTranslatesAutoresizingMaskIntoConstraints(false)

        super.init(frame: frame)

        self.setTranslatesAutoresizingMaskIntoConstraints(true)
        self.addSubviews()
    }

    convenience init () {
        self.init(frame: CGRectZero)
    }

    required init(coder aDecoder: NSCoder) {
        fatalError("DropdownTitleView does not support NSCoding")
    }

    private func addSubviews() {
        addSubview(titleLabel)
        addSubview(arrowImageView)
    }

    // MARK: - Methods

    func setTitle(title: String) {
        titleLabel.text = title
        titleLabel.sizeToFit()
        setNeedsUpdateConstraints()
    }

    // MARK: - Layout

    override func updateConstraints() {
        removeConstraints(self.constraints())

        let viewsDictionary = ["titleLabel": titleLabel, "arrowImageView": arrowImageView]
        var constraints: [AnyObject] = []

        constraints.extend(NSLayoutConstraint.constraintsWithVisualFormat("H:|[titleLabel]-8-[arrowImageView]|", options: .AlignAllBaseline, metrics: nil, views: viewsDictionary))
        constraints.extend(NSLayoutConstraint.constraintsWithVisualFormat("V:|[titleLabel]|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDictionary))

        self.addConstraints(constraints)

        super.updateConstraints()
    }

    override func sizeThatFits(size: CGSize) -> CGSize {
        // +8.0 - distance between image and text
        let width = CGRectGetWidth(arrowImageView.bounds) + CGRectGetWidth(titleLabel.bounds) + 8.0
        let height = max(CGRectGetHeight(arrowImageView.bounds), CGRectGetHeight(titleLabel.bounds))
        return CGSizeMake(width, height)
    }
}

and ViewController:

override func viewDidLoad() {
    super.viewDidLoad()

    // Set custom title view to show arrow image along with title
    self.navigationItem.titleView = dropdownTitleView

    // your code ...
}

private func updateTitleView(title: String) {
    // update text
    dropdownTitleView.setTitle(title)

    // layout title view
    dropdownTitleView.sizeToFit()
    self.navigationController?.navigationBar.setNeedsLayout()
}

Tags:

Ios

Nslayoutconstraint

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