Understanding Gesture Recognizers and UIButton Tag

As a developer, it’s not uncommon to encounter unexpected behavior when working with gesture recognizers and user interface components like UIButton. In this article, we’ll delve into the world of gesture recognizers, explore why the UIButton tag may not be what you expect on long press, and provide a solution to achieve your desired outcome.

What are Gesture Recognizers?

Gesture recognizers are used to detect and respond to specific gestures, such as taps, pinches, or swipes. In iOS development, there are several types of gesture recognizers available, including:

• UIGestureRecognizer: A base class for all gesture recognizers.
• UILongPressGestureRecognizer: Detects a long press on a view.

Understanding UIButton Tag

When working with UIButton, it’s common to associate a tag with the button. This tag can be used to identify the button and perform specific actions or handle events. In this case, the developer wants to access the tag of the UIButton when a long press gesture is detected.

- (IBAction)longPress:(id)sender {
    UILongPressGestureRecognizer* gesture=(UILongPressGestureRecognizer*)sender;
    NSLog(@"Tag---> %d",gesture.view.tag);
}

However, as we’ll explore in the next section, this approach may not yield the expected results due to how gesture recognizers work.

Why Gesture Recognizer View Property May Not Work as Expected

When working with UILongPressGestureRecognizer, it’s essential to understand how the view property of the gesture recognizer works. According to Apple’s documentation:

“A gesture recognizer operates on touches hit-tested to a specific view and all of that view’s subviews. It thus must be associated with that view. To make that association you must call the UIView method addGestureRecognizer:. A gesture recognizer does not participate in the view’s responder chain.”

In other words, when a gesture recognizer is attached to a view, it only tracks touches within that view and its subviews. However, this doesn’t mean the gesture recognizer’s view property will always return the same view.

Here’s an example of how this might happen:

// Create two UIButtons with different tags.
UIButton* button1 = [UIButton buttonWithType:UIButtonTypeCustom];
button1.tag = 100;

UIButton* button2 = [UIButton buttonWithType:UIButtonTypeCustom];
button2.tag = 200;

Now, let’s add a UILongPressGestureRecognizer to both buttons and check the view property of the gesture recognizer.

// Add UILongPressGestureRecognizer to both buttons.
UILongPressGestureRecognizer* longPress1 = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];
longPress1.view = button1;
button1.addGestureRecognizer(longPress1);

UILongPressGestureRecognizer* longPress2 = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];
longPress2.view = button2;
button2.addGestureRecognizer(longPress2);

- (IBAction)longPress:(id)sender {
    NSLog(@"View: %@", sender.view);
}

As you can see, the view property of both gesture recognizers is not necessarily the same view.

Solution: Using a Unique Gesture Recognizer for Each View

To solve this issue, we need to create a unique gesture recognizer for each view that needs recognizing. This way, when we access the tag property of the button, we can be sure it’s the correct one.

Here’s how you can do it:

// Create a custom class that inherits from UIButton.
@interface MyCustomButton : UIButton

@property (nonatomic) NSInteger tag;

@end

@implementation MyCustomButton

- (instancetype)initWithTag:(NSInteger)arg1 {
    self = [super init];
    if (self) {
        _tag = arg1;
    }
    return self;
}

@end

Now, let’s create a custom class that inherits from UIButton and adds the tag property:

// Create an array of MyCustomButton instances.
NSArray<MyCustomButton*>* buttons = @[];
for (int i = 0; i < 12; i++) {
    MyCustomButton* button = [[MyCustomButton alloc] initWithTag:i];
    [buttons addObject:button];
}

Next, we’ll create a unique gesture recognizer for each view and set the tag property of the corresponding button:

// Create an array of UILongPressGestureRecognizer instances.
NSArray<UILongPressGestureRecognizer*>* longPressRecognizers = @[];
for (int i = 0; i < buttons.count; i++) {
    MyCustomButton* button = buttons[i];
    
    // Create a unique gesture recognizer for each view.
    UILongPressGestureRecognizer* longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];
    longPress.view = button;
    [longPressRecognizers addObject:longPress];
}

Finally, we’ll add the gesture recognizers to their corresponding views and set the delegate:

// Set the delegate for each gesture recognizer.
longPressRecognizers[0].delegate = self;

// Add the gesture recognizers to their views.
for (int i = 0; i < longPressRecognizers.count; i++) {
    UILongPressGestureRecognizer* longPress = longPressRecognizers[i];
    longPress.view.tag = i;
    [longPressRecognizers[i].view addGestureRecognizer:longPress];
}

With this approach, we can now access the correct tag property of each button when a long press gesture is detected.

- (IBAction)longPress:(id)sender {
    NSLog(@"Tag: %d", sender.view.tag);
}

Conclusion

In conclusion, when working with gesture recognizers and UIButton in iOS development, it’s essential to understand how the view property of the gesture recognizer works. By creating a unique gesture recognizer for each view that needs recognizing, we can ensure that the correct button is accessed when a long press gesture is detected.

By following these steps and using a custom class to inherit from UIButton, you can solve the issue of getting the wrong UIButton tag on long press gestures.

Last modified on 2025-03-16