Question

I have a two UIViews filled with UIButtons. I want to only allow one button to accept touches at a time PER UIView. That is to say I want multitouch working if you have one finger in each group of buttons but not if you have both fingers in the same group.

Of course exclusiveTouch set on the buttons makes sure only one button at a time is touched but it does it for the entire window. Is there a way to only allow one touch per UIView instead of the entire window?

Update: So to give a better understand of the desired function. I want a user to be able to select a red and blue card using multitouch. Easy. BUT I don’t want them to be able to select two red cards or anything like that. Problem is if I turn on exclusiveTouch on the cards only one card in the WHOLE WINDOW can be selected at a time. The desired functionality is to have exclusiveTouch only operate PER UIVIEW which each set of cards is wrapped in its own UIView already.

Update 2: Just wanted to throw in that I am trying to find a solution that DOESN’T involve subclassing or otherwise overriding UIView’s touch controllers. That is a last resort.

Answer 1

When touching down one of your buttons, you may set userInteractionEnabled property of another button to NO and set it back to YES while touching up.

UPDATE 1

Sorry, I was an idiot.

UPDATE 2

…

UPDATE 3

Finally I got back to XCode. This code works (if I understood your aim correctly):

@interface ViewController : UIViewController {
    NSMutableArray *leftButtonsArray;
    NSMutableArray *rightButtonsArray;
}

@end

//

@implementation ViewController

#pragma mark - Objects Processing

- (void)buttonDownAct:(UIButton *)sender {
    sender.backgroundColor = [UIColor greenColor];

    NSArray *targetArray = nil;
    if ([leftButtonsArray indexOfObject:sender] == NSNotFound)
        targetArray = rightButtonsArray;
    else
        targetArray = leftButtonsArray;

    for (UIButton *button in targetArray)
        if (button != sender)
            button.userInteractionEnabled = NO;
}
- (void)buttonUpAct:(UIButton *)sender {
    NSArray *targetArray = nil;
    if ([leftButtonsArray indexOfObject:sender] == NSNotFound) {
        targetArray = rightButtonsArray;
        sender.backgroundColor = [UIColor blueColor];
    }
    else {
        targetArray = leftButtonsArray;
        sender.backgroundColor = [UIColor redColor];
    }

    for (UIButton *button in targetArray)
        button.userInteractionEnabled = YES;
}

#pragma mark - View lifecycle

- (void)loadView {
    leftButtonsArray = [[NSMutableArray alloc] init];
    rightButtonsArray = [[NSMutableArray alloc] init];

    self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    self.view.backgroundColor = [UIColor whiteColor];
    float desiredWidth = self.view.frame.size.width / 4, desiredHeight = self.view.frame.size.height / 2;

    for (int i = 0; i < 4; i++) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        button.frame = CGRectInset(CGRectMake(desiredWidth * (i % 2), desiredHeight * (i / 2), desiredWidth, desiredHeight), 10, 10);
        [button setBackgroundColor:[UIColor redColor]];
        [button addTarget:self action:@selector(buttonDownAct:) forControlEvents:UIControlEventTouchDown];
        [button addTarget:self action:@selector(buttonUpAct:) forControlEvents:UIControlEventTouchUpInside | UIControlEventTouchUpOutside];

        [self.view addSubview:button];
        [leftButtonsArray addObject:button];
    }

    for (int i = 0; i < 4; i++) {
        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
        button.frame = CGRectInset(CGRectOffset(CGRectMake(desiredWidth * (i % 2), desiredHeight * (i / 2), desiredWidth, desiredHeight), self.view.frame.size.width / 2, 0), 10, 10);
        [button setBackgroundColor:[UIColor blueColor]];
        [button addTarget:self action:@selector(buttonDownAct:) forControlEvents:UIControlEventTouchDown];
        [button addTarget:self action:@selector(buttonUpAct:) forControlEvents:UIControlEventTouchUpInside | UIControlEventTouchUpOutside];

        [self.view addSubview:button];
        [rightButtonsArray addObject:button];
    }
}

@end