Understanding UILabel Dynamic Height in iOS

In this article, we’ll delve into the complexities of achieving dynamic height for UILabel instances in iOS. We’ll explore the limitations and potential solutions to get your label to adapt its height based on the text content, while maintaining consistency across portrait and landscape orientations.

Background and Requirements

When it comes to setting a label’s font size or font, there are many factors at play, such as the width of the parent view, available space within the parent, and line break modes. In iOS, you can adjust these properties by using various methods like sizeWithFont:constrainedToSize:lineBreakMode:.

However, this method is not foolproof. For instance, when setting the font size dynamically based on a label’s width, it may lead to inconsistent heights across different orientations due to varying available space.

Why Doesn’t sizeWithFont:constrainedToSize:lineBreakMode: Work?

The sizeWithFont:constrainedToSize:lineBreakMode: method is intended to determine the optimal font size for your given label’s width while respecting any constraints you’ve set. In our previous example, we used this method with a constrained maximum height, hoping it would help achieve dynamic labeling.

Unfortunately, this approach has limitations. By using CGFLOAT_MAX as the maximum width, the sizeWithFont:constrainedToSize:lineBreakMode: method will return the same height regardless of whether you’re in portrait or landscape orientation because there is enough space to fit two lines of text in both orientations.

Moreover, by setting the line break mode to word wrap and using a label’s own bounds size for width constraints, we create an inconsistent layout when switching between orientations. If our labels have different heights across orientations due to their varying content sizes, we end up with ugly, misaligned text layouts that can negatively impact user experience.

Solving the Problem: Using CGFLOAT_MAX

To solve this problem and get dynamic height working for your UILabel instances in iOS, you need to use a different approach. When trying to set the label’s size based on its content, we must ensure our layout takes into account potential changes when switching between orientations.

Here’s how you can achieve it:

New Setup for Dynamic Label Height

Firstly, we will create an instance variable of your view and update the frame accordingly.

@interface ViewController () <UITableViewDataSource>
@property (nonatomic) BOOL isLandscape;
@end

Next, set a new instance variable to control your label size. You can do this by overriding the viewWillLayoutSubviews method in your view controller.

- (void)viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];
    
    // Set up label height based on screen width and orientation
    CGSize maximumLabelSize = CGSizeMake(self.view.bounds.size.width, CGFLOAT_MAX);
    CGSize titleSize = [self.newsAsset.title sizeWithFont:[UIFont boldSystemFontOfSize:18.0] constrainedToSize:maximumLabelSize lineBreakMode: self.label.lineBreakMode];
    
    if (self.isLandscape) {
        // Landscape
        self.label.frame.size.height = titleSize.height;
    } else {
        // Portrait
        [self.label sizeToFit];
        self.label.frame.size.height = self.label.bounds.size.height;
    }
}

In this example, we use sizeWithFont:constrainedToSize:lineBreakMode: with the maximum width set to CGFLOAT_MAX. This allows us to get an accurate height for our label’s content. We also store its size in a variable called titleSize.

Then, in the viewWillLayoutSubviews method, we check if we are currently in landscape or portrait orientation and apply these settings accordingly.

This setup ensures that your labels will have dynamic heights based on their text contents while maintaining consistency across different orientations.

Note: Make sure to update this code with your actual label name (self.newsAsset.title) as per your requirement.

Handling Orientation

To ensure our app adapts well to both portrait and landscape modes, we need to handle orientation changes in the viewDidLoad method:

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Set up rotation observer
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:nil];
}

And don’t forget to remove the observer in dealloc:

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

In our orientationChanged: method, we update the view’s orientation flag and set it as needed for your view.

Here is a more complete code snippet with the above setup.

Complete Example

#import <UIKit/UIKit.h>

@interface ViewController () <UITableViewDataSource>
@property (nonatomic) BOOL isLandscape;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Set up rotation observer
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:nil];
}

- (void)orientationChanged:(NSNotification *)notification {
    self.isLandscape = [[UIDevice currentDevice] orientations].containsObject(UIInterfaceOrientationLandscapeLeft);
    [self viewWillLayoutSubviews];
    self.view.layoutIfNeeded;
}

- (void)viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];
    
    // Set up label height based on screen width and orientation
    CGSize maximumLabelSize = CGSizeMake(self.view.bounds.size.width, CGFLOAT_MAX);
    CGSize titleSize = [self.newsAsset.title sizeWithFont:[UIFont boldSystemFontOfSize:18.0] constrainedToSize:maximumLabelSize lineBreakMode: self.label.lineBreakMode];
    
    if (self.isLandscape) {
        // Landscape
        self.label.frame.size.height = titleSize.height;
    } else {
        // Portrait
        [self.label sizeToFit];
        self.label.frame.size.height = self.label.bounds.size.height;
    }
}

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

@end

@interface ViewController () <UITableViewDataSource>
@property (nonatomic, strong) UILabel *label;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // Set up label
    self.label = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 300, 50)];
    self.label.font = [UIFont boldSystemFontOfSize:18.0];
    self.label.lineBreakMode = UILineBreakModeWordWrap;
    self.view.addSubview(self.label);

    // Set up news asset
    _newsAsset = [[NewsAsset alloc] init];

    // ... other code ...
}

@end

Last modified on 2025-02-02