On a UILongPressGestureRecognizer how do I detect which object generated the event?

Question

I have a view with several UIButtons. I have successfully implemented using UILongPressGestureRecognizer with the following as the selector;

- (void)longPress:(         


        

Answer 1

If your view contains multiple subViews (like lots of buttons) you can determine what was tapped:

// Get the position of the point tapped in the window co-ordinate system
CGPoint tapPoint = [gesture locationInView:nil];

UIView *viewAtBottomOfHeirachy = [self.window hitTest:tapPoint withEvent:nil];

if ([viewAtBottomOfHeirachy isKindOfClass:[UIButton class]])

Answer 2

This is available in gesture.view.

Answer 3

Are you adding the long tap gesture controller to the UIView that has the UIButtons as subviews? If so, something along the lines of @Magic Bullet Dave's approach is probably the way to go.

An alternative is to subclass UIButton and add to each UIButton a longTapGestureRecogniser. You can then get your button to do what you like. For example, it could send a message identifying itself to a view controller. The following snippet illustrates methods for the subclass.

- (void) setupLongPressForTarget: (id) target;
{
    [self setTarget: target];  // property used to hold target (add @property and @synthesise as appropriate)

    UILongPressGestureRecognizer* longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:button action:@selector(longPress:)];
    [self addGestureRecognizer:longPress];
    [longPress release];
}

- (void) longPress: (UIGestureRecognizer*) recogniser;
{
    if (![recogniser isEnabled]) return; // code to prevent multiple long press messages
    [recogniser setEnabled:NO];
    [recogniser performSelector:@selector(setEnabled:) withObject: [NSNumber numberWithBool:YES] afterDelay:0.2];

    NSLog(@"long press detected on button"); 

    if ([[self target] respondsToSelector:@selector(longPressOnButton:)])
    {
        [[self target] longPressOnButton: self];
    }
}

In your view controller you might have code something like this:

- (void) viewDidLoad;
{
    // set up buttons (if not already done in Interface Builder)

    [buttonA setupLongPressForTarget: self];
    [buttonB setupLongPressForTarget: self];

    // finish any other set up
}

- (void) longPressOnButton: (id) sender;
{
     if (sender = [self buttonA])
     {
         // handle button A long press
     }

    if (sender = [self buttonB])
     {
         // handle button B long press
     }

     // etc.

 }