Understanding the Issue with iOS 5 Custom View Controller Blocks Scroll View on a Custom Container View Controller

Introduction

In this article, we’ll delve into the intricacies of custom view controller blocks and their interactions with scroll views in iOS. Specifically, we’ll explore the challenges faced by developers when trying to create a custom container view controller that manages multiple child view controllers, each of which has its own scroll view.

Background

For backward compatibility purposes, some developers may still be using iOS 5, which introduces the concept of custom view controllers through Storyboarding. These custom view controllers can display different content and interact with their parent view controllers in unique ways. However, creating a custom container view controller that manages multiple child view controllers with scroll views can be tricky.

In this article, we’ll examine the code provided by the developer who’s experiencing issues with his custom container view controller blocking the scroll view on iOS 5. We’ll break down the problem and offer solutions to help you overcome similar challenges when working with custom view controllers and scroll views.

Understanding the Code

The provided code snippet shows the implementation of a main view controller that has a horizontal scroll menu. The scroll menu consists of multiple buttons, each displaying different content. When a button is tapped, it triggers an action that displays a new child view controller containing the relevant content.

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Set up the scroll view
    self.menuScrollView.frame = CGRectMake(0, kScrollViewMarginTop, self.view.frame.size.width, kScrollViewHeight);
    self.menuScrollView.showsHorizontalScrollIndicator = NO;
    self.menuScrollView.pagingEnabled = YES;
    
    // Select the first button initially
    self.firstMenuButton.selected = YES;
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    
    // Update the scroll view content size
    self.menuScrollView.contentSize = CGSizeMake(kScrollViewContentWidth, kScrollViewHeight);
}

- (IBAction)menuButtonTapped:(id)sender {
    UIButton *button = (UIButton *)sender;
    
    switch (button.tag) {
        case 0:
            if (![self.firstMenuButton isSelected]) {
                self.firstMenuButton.selected = YES;
                [self.firstMenuButton setBackgroundImage:[UIImage imageNamed:@"firstMenuButton_selected.png"] forState:UIControlStateSelected];
                [self deselectButtonsExceptButtonWithTag:button.tag];
                
                // Show the first content
                UIViewController *contentViewController = (UITableViewController *)[self.storyboard instantiateViewControllerWithIdentifier:@"firstControllerStoryboardID"];
                [self displayContentViewController:contentViewController];
            }
            break;
        default:
            break;
    }
}

- (void)displayContentViewController:(UIViewController *)viewController {
    [self addChildViewController:viewController];
    
    viewController.view.frame = CGRectMake(0, self.menuScrollView.frame.origin.y + self.menuScrollView.frame.size.height + 5.0, 320.0, 200.0);
    
    [self.view addSubview:viewController.view];
    [viewController didMoveToParentViewController:self];
}

The Problem

The problem with the provided code lies in the way it creates and displays child view controllers with scroll views. When a button is tapped, it triggers an action that displays a new child view controller using self.storyboard instantiateViewControllerWithIdentifier:@"firstControllerStoryboardID". However, this approach blocks the scroll view, preventing further scrolling.

Solution

To overcome this issue, we need to understand how Auto Layout works in Storyboarding and how to disable its constraints on our custom container view controller. In iOS 5, Auto Layout is enabled by default for all views, including UIViewController instances.

One possible solution involves disabling Auto Layout on the child view controllers with scroll views. To achieve this, we can use the following approach:

Create a new view controller that will act as our custom container view controller.
In this container view controller, create multiple child view controllers and set their scroll views to be disabled using Auto Layout constraints.
When a button is tapped, display the desired child view controller by pushing it onto the navigation stack.

Here’s an updated code snippet demonstrating this approach:

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Create a new container view controller
    self.containerViewController = [[ContainerViewController alloc] init];
    [self addChildViewController:self.containerViewController];
}

// Disable Auto Layout on the child view controllers with scroll views
- (void)configureChildViewControllers {
    for (int i = 0; i < numberOfChildViewControllers; i++) {
        UIViewController *childViewController = [self.child View Controllers objectAtIndex:i];
        
        // Create a constraint that sets the scroll view's content size to be equal to its frame size
        NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:childViewController.view attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNone multiplier:1 constant:kScrollViewContentWidth];
        [self.containerViewController.view addConstraint:constraint];
        
        // Disable Auto Layout on the child view controller's scroll view
        NS.ConstraintDescription *scrollViewConstraints = [NSLayoutConstraint constraintDescriptionWithKey:@"scrollViewConstraints"];
        NSArray *constraints = self.containerViewController.view.constraints;
        for (NSLayoutConstraint *constraint in constraints) {
            if ([constraint constraintDescription] == scrollViewConstraints) {
                constraint.constant = 0;
                break;
            }
        }
    }
}

// Push the desired child view controller onto the navigation stack when a button is tapped
- (IBAction)menuButtonTapped:(id)sender {
    UIButton *button = (UIButton *)sender;
    
    // ...
    
    // Get the index of the selected button
    int selectedIndex = button.tag - 1;
    
    // Push the desired child view controller onto the navigation stack
    [self.containerViewController pushChildViewController:[self.childViewControllers objectAtIndex:selectedIndex]];
}

Conclusion

In this article, we’ve examined the code provided by a developer who’s experiencing issues with his custom container view controller blocking the scroll view on iOS 5. We’ve broken down the problem and offered solutions to help you overcome similar challenges when working with custom view controllers and scroll views.

By disabling Auto Layout on child view controllers with scroll views, we can prevent the scroll view from being blocked by the container view controller. This approach requires careful planning and configuration of constraints, but it provides a reliable solution for managing multiple child view controllers with scroll views in your app.

Last modified on 2025-04-04