UIButton not responding when it overlaps another UIButton

Introduction

In iOS development, using UIButtons can be a straightforward way to create interactive elements in our user interfaces. However, there’s a common issue that developers encounter: when one UIButton overlaps another, the overlapping button may not respond to touch events or other interactions. In this article, we will explore why this happens and how you can resolve it.

Understanding the Problem

To grasp the root cause of the issue, let’s consider a simplified scenario:

We have a UIViewController called MyViewController.
The view of MyViewController has an instance of UIButton called MyFirstButton as a subview.
Additionally, MySubView, another subview of MyViewController's view, is placed directly over MyFirstButton.

Now, suppose the frame of MySecondButton (a subview of MySubView) overlaps the frame of MyFirstButton. When you attempt to tap on MySecondButton, it doesn’t respond to touch events. This is because the system can’t determine which button was actually tapped.

Why Does This Happen?

The problem lies in how the UIButton handles touch events. When a finger touches a view, the system sends an event to all views that intersect with the point of contact. In this case:

If MySecondButton covers MyFirstButton, it will receive the touch event.
Since MySubView contains both buttons and intersects with the touch point, it receives the event instead.

This means that the system can’t determine which button was actually tapped when the touch occurs within the overlapping area of MyFirstButton.

Solution

One possible solution to this issue is not directly altering the behavior of the individual buttons but hiding one of them when another overlaps. Here’s how you could implement it:

Step 1: Create a new ViewController

Create a separate ViewController (e.g., OverlayView) that will be responsible for overlaying on top of MyFirstButton.

// OverlayView.h
#import <UIKit/UIKit.h>

@interface OverlayView : UIViewController

@end

// OverlayView.m
#import "OverlayView.h"

@implementation OverlayView

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // Create a button to hold the overlay functionality
        UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
        button.frame = frame;
        // Add an action to toggle the visible state of MyFirstButton
        [button addTarget:self action:@selector(toggleVisibility:) forControlEvents:UIControlEventTouchUpInside];
        [self.view addSubview:button];
    }
    return self;
}

- (void)toggleVisibility:(UIButton *)sender {
    if (sender.tag == 0) {
        // Toggle visibility for MySecondButton
        sender.tag = 1;
        // Change button color
        sender.backgroundColor = [UIColor redColor];
        
        // Update visible state of MyFirstButton
        UIButton *firstButton = [[UIButton alloc] initWithFrame:sender.frame];
        firstButton.tag = 0;
        firstButton.backgroundColor = [UIColor blueColor]; // Change color back to original when overlayed.
        [self.view addSubview:firstButton];
    } else {
        sender.tag = 0;
        // Remove MySecondButton from view
        UIButton *secondButton = (UIButton *)[self.view viewWithTag:1];
        if (secondButton) {
            [secondButton removeFromSuperview];
            // Change button color back to original when hidden.
            secondButton.backgroundColor = [UIColor blueColor]; // Color change will be reverted here.
        }
    }
}

@end

Step 2: Implement Button Creation

Modify the creation of MyFirstButton in your main view controller’s code:

// MyViewController.m
#import "MyViewController.h"
#import "OverlayView.h"

@implementation MyViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Create and add buttons to the main view
    UIButton *firstButton = [[UIButton alloc] initWithFrame:CGRectZero];
    firstButton.backgroundColor = [UIColor blueColor];
    [self.view addSubview:firstButton];
    
    OverlayView *overlayView = [[OverlayView alloc] initWithFrame:firstButton.frame];
    overlayView.tag = 2;
    [self.view insertSubview:overlayView atIndex:1];
}

@end

Step 3: Setting Initial Visibility

Add initial visibility to MyFirstButton in the main view controller.

// MyViewController.m
#import "MyViewController.h"
#import "OverlayView.h"

@implementation MyViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Create and add buttons to the main view
    UIButton *firstButton = [[UIButton alloc] initWithFrame:CGRectZero];
    firstButton.backgroundColor = [UIColor blueColor];
    [self.view addSubview:firstButton];
    
    OverlayView *overlayView = [[OverlayView alloc] initWithFrame:firstButton.frame];
    overlayView.tag = 2;
    [self.view insertSubview:overlayView atIndex:1];
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear];
    
    // Initially show MyFirstButton
    UIButton *firstButton = self.view.subviewWithTag:0;
    if (firstButton) {
        firstButton.backgroundColor = [UIColor blueColor];
    }
}

@end

This implementation hides MySecondButton when you tap on it, revealing MyFirstButton. When you tap on MyFirstButton, its color changes to red. This allows the system to determine which button was tapped and respond accordingly.

Conclusion

Resolving the issue of a UIButton not responding when overlapped by another involves implementing some creative logic for overlaying views and managing their interactions. While this approach can be somewhat more complicated, it also provides flexibility in terms of how your buttons are managed within the overall hierarchy of your user interface.

By using an overlay view that holds an action to toggle visibility between MyFirstButton and MySecondButton, you effectively force the system to determine which button was tapped by changing their visible states on a per-touch basis.

Last modified on 2023-06-24