Resizing a UIView when Rotated to Landscape and Back

In this article, we’ll explore the best method to resize a UIView when rotated to landscape and back in iOS. We’ll dive into the code, discuss the design considerations, and provide examples to illustrate the solution.

Understanding the Problem

When rotating a view from portrait to landscape or vice versa, the frame of the view changes. If we don’t adjust the constraints accordingly, the view may not resize as expected. In this case, we want to resize our UIView (which contains a UIScrollView) when rotated to landscape and back, while maintaining a fixed height in portrait.

Background: Understanding View Layout

To understand how views are laid out in iOS, let’s take a look at the view hierarchy:

• Window: The top-most view in the app’s hierarchy.
• ViewController: A subclass of UIViewController, which manages the view controller’s lifecycle and layout.
• UIView: A subclass of UIView, which represents a single view in the view hierarchy.
• UIScrollView: A subclass of UIView, which provides a scrollable area for content.

When a view is rotated, its frame changes. The viewWillLayoutSubviews method is called when this happens, allowing us to adjust our layout accordingly.

Design Considerations

Before we dive into the code, let’s consider some design considerations:

• Constraints: Constraints are used to define relationships between views in a view hierarchy. By adjusting constraints, we can resize our UIView.
• Frames: Frames represent the boundaries of a view and are affected when it’s rotated.
• Layout Subviews: The layoutSubviews method is called after layout has completed, allowing us to make final adjustments.

Solution Overview

Our approach will be to:

1. Update our layout subviews when the device orientation changes.
2. Adjust the constraints of our view hierarchy accordingly.

We’ll start by examining how we can update our layout subviews in GraphView.m and ViewController.

GraphView.m: Updating Layout Subviews

In GraphView.m, we’re using a custom method called updateViewDimensions to set up the frame of our UIScrollView. We also need to keep track of the screen width and height.

// Define variables for screen width and height
CGFloat kViewWidth;
CGFloat kViewHeight;

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    
    // Update variables for screen width and height
    kViewWidth = GET_SCREEN_WIDTH_HERE;
    kViewHeight = GET_SCREEN_HEIGHT_HERE;
    
    // Call updateViewDimensions to set the frame of UIScrollView and UIView
    [self updateViewDimensions];
}

ViewController.m: Adjusting Constraints

In ViewController, we’re using another custom method called updateConstraints to adjust our view hierarchy’s constraints when the device orientation changes.

- (void)viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];
    
    // Check if the device is in landscape mode
    CGFloat deviceOrientation = [[UIDevice currentDevice] orientation];
    if (deviceOrientation == UIDeviceOrientationLandscapeLeft || deviceOrientation == UIDeviceOrientationLandscapeRight) {
        // Update constraints to resize UIView when rotated
        _graphViewHeightConstraint.constant = kScreenHeight - self.navigationController.navigationBar.frame.size.height;
    } else {
        // Update constraints to maintain fixed height in portrait mode
        _graphViewHeightConstraint.constant = 300;
    }
}

Implementing the Solution

To implement our solution, we’ll need to:

1. Define a method updateConstraints to adjust our view hierarchy’s constraints when the device orientation changes.
2. Call this method in viewDidLayoutSubviews.

Here’s how you can do it:

- (void)updateConstraints {
    // Update constraints to resize UIView when rotated
    if ([[UIDevice currentDevice] orientation] == UIDeviceOrientationLandscapeLeft || [[UIDevice currentDevice] orientation] == UIDeviceOrientationLandscapeRight) {
        _graphViewHeightConstraint.constant = kScreenHeight - self.navigationController.navigationBar.frame.size.height;
    } else {
        // Update constraints to maintain fixed height in portrait mode
        _graphViewHeightConstraint.constant = 300;
    }
    
    // Call super's updateConstraints method
    [super updateConstraints];
}

Conclusion

Resizing a UIView when rotated to landscape and back can be challenging, but it’s achievable by using the right layout subviews and constraints. In this article, we’ve explored how to use our custom methods to adjust our view hierarchy’s constraints when the device orientation changes.

We hope that this tutorial has provided you with a solid understanding of how to implement a similar solution in your own iOS projects.

Example Use Case

Here is an example of what the updated GraphView.m and ViewController.m files might look like:

// GraphView.m
#import <UIKit/UIKit.h>

@interface GraphView : UIView {
    CGFloat kScreenHeight;
    CGFloat kScreenWidth;
    CGFloat kDistanceToTopView;
}

@property (nonatomic) CGFloat graphHeight;

- (void)updateViewDimensions {
    // Update frame of UIScrollView and UIView
    self.frame = CGRectMake(0, 0, self.kScreenWidth, self.kScreenHeight - self.navigationController.navigationBar.frame.size.height);
    
    // Update frame of yourView
    yourView.frame = CGRectMake(self.kDistanceToTopView, self.kScreenHeight - self.navigationController.navigationBar.frame.size.height, self.kScreenWidth, self.graphHeight);
}

@end

@implementation GraphView {
    CGFloat kViewXStartsFrom;
    CGFloat kViewYStartsFrom;
}

// ViewController.m
#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@property (nonatomic) IBOutlet UIView *graphView;

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Initialize graph view height constraint
    self.graphView.heightConstraint.constant = 300;
}

@end

Note that the code above assumes a UIView as your view, and you should adjust this to fit your needs.

Last modified on 2023-08-16