Pass touch to nearest UIButton? - ios

Question

I am trying to create a view with multiple UIButtons where any tap would be registered as a tap on the nearest UIButton. I have been unsuccessful so far, and I am hoping you guys/gals have some knowledge on standard approaches/methods used to do what I am trying to do.

Answer 1

You could use the Touches Began method:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
// Get the CGPoint of the touch:
UITouch touch = [touches anyObject];
CGPoint touchPoint = [touch locationInView:self.view];
// Loop through an array containing your buttons and see if we tapped
// one of these buttons, if so, do nothing and let the button handle the tap
for (UIButton button in MyButtonsArray){
if(CGRectContainsPoint(button.frame, touchPoint)) {
return;
}
}
// if the loop completes without returning, you tapped something other than a button
// so add code here that uses the mathematical distance formula to
// calculate which button is the closest to the tap point.
}
You have all the necessary "data" in terms of coordinates of the button and coordinates of the touch point to calculate the closest button to the touch point.

Answer 2

that's why I am assuming that simply passing the touch to the nearest UIButton would be more practical.
No, you should place rectangle buttons next to each other and do the hit testing to determine if the touch was within the irregular shaped area.
See my blog post Hit Testing Done Right how to test with a shaped layer. There it uses a UIView, but as UIButton inherits from UIView, it would work the same, if you subclass like
#interface MyButton : UIButton
#implementation MyButton
//
// ...
//
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
CGPoint p = [self convertPoint:point toView:[self superview]];
if(self.layer.mask){ // a layer's mask is found. Mask can be any CGPath
if (CGPathContainsPoint([(CAShapeLayer *)self.layer.mask path], NULL, p, YES) )
return YES;
}else {
if(CGRectContainsPoint(self.layer.frame, p))
return YES;
}
return NO;
}
#end
If you want to work with partially transparent images, have a look at OBShapedButton, where alpha of a certain threshold will determine if the button was hit or not. But as mine path based approach it does so by overwriting -pointInside:withEvent:
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
// Return NO if even super returns NO (i.e., if point lies outside our bounds)
BOOL superResult = [super pointInside:point withEvent:event];
if (!superResult) {
return superResult;
}
// Don't check again if we just queried the same point
// (because pointInside:withEvent: gets often called multiple times)
if (CGPointEqualToPoint(point, self.previousTouchPoint)) {
return self.previousTouchHitTestResponse;
} else {
self.previousTouchPoint = point;
}
BOOL response = NO;
if (self.buttonImage == nil && self.buttonBackground == nil) {
response = YES;
}
else if (self.buttonImage != nil && self.buttonBackground == nil) {
response = [self isAlphaVisibleAtPoint:point forImage:self.buttonImage];
}
else if (self.buttonImage == nil && self.buttonBackground != nil) {
response = [self isAlphaVisibleAtPoint:point forImage:self.buttonBackground];
}
else {
if ([self isAlphaVisibleAtPoint:point forImage:self.buttonImage]) {
response = YES;
} else {
response = [self isAlphaVisibleAtPoint:point forImage:self.buttonBackground];
}
}
self.previousTouchHitTestResponse = response;
return response;
}