Handling touches in CALayer - ios

Question

I'm trying to detect touches in my view.
My code:
- (CALayer *)layerForTouch:(UITouch *)touch {
UIView *view = self;
CGPoint location = [touch locationInView:view];
location = [view convertPoint:location toView:nil];
CALayer *hitPresentationLayer = [view.layer.presentationLayer hitTest:location];
if (hitPresentationLayer) {
return hitPresentationLayer.modelLayer;
}
return nil;
}
But I found problem. It's detecting just first layer in tree.
Every figure on screenshot - one layer. I'm drawing it's from the biggest to the smallest as tree.

Answer 1

if your topmost layer covers the whole screen (or other below layers) then yes you will get the top most layer during hitTest check. you can do a containsPoint check for all your layers if you want to check it further below. Do find some sample code below
#interface ViewController ()
#property (nonatomic, strong) CALayer *layer1;
#property (nonatomic, strong) CALayer *layer2;
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
CALayer *layer = [[CALayer alloc] init];
layer.frame = (CGRect) { 10, 10, 100, 100 };
[self.view.layer addSublayer:layer];
layer.backgroundColor = [UIColor redColor].CGColor;
self.layer1 = layer;
layer = [[CALayer alloc] init];
layer.frame = (CGRect) { 60, 60, 100, 100 };
[self.view.layer addSublayer:layer];
layer.backgroundColor = [UIColor blueColor].CGColor;
self.layer2 = layer;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint touchPoint = [(UITouch*)[touches anyObject] locationInView:self.view];
CALayer *touchedLayer = [self.view.layer.presentationLayer hitTest:touchPoint];
CALayer *originalLayer = [touchedLayer modelLayer];
if (originalLayer == self.layer1) { NSLog(#"layer 1 touched"); }
if (originalLayer == self.layer2) { NSLog(#"layer 2 touched"); }
for ( CALayer *layer in #[self.layer1, self.layer2])
{
CGPoint point = [layer convertPoint:touchPoint fromLayer:self.view.layer];
NSLog(#"layer %# containsPoint ? %#",layer, [layer containsPoint:point]? #"YES":#"NO");
NSLog(#"original point : %# | converted point : %#",NSStringFromCGPoint(touchPoint),NSStringFromCGPoint(point));
}
}
#end
Or you can try using CAShapeLayers & match with the CGPath of ShapeLayer to see if its touched like the example below ..
#interface ViewController ()
#property (nonatomic, strong) CALayer *layer1;
#property (nonatomic, strong) CALayer *layer2;
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
CAShapeLayer *shapeLayer = [[CAShapeLayer alloc] init];
shapeLayer.path = [UIBezierPath bezierPathWithRect:(CGRect){ 0,0,100,10 }].CGPath;
shapeLayer.backgroundColor = [UIColor redColor].CGColor;
shapeLayer.frame = (CGRect){20, 20, 100, 100};
[self.view.layer addSublayer:shapeLayer];
self.layer1 = shapeLayer;
shapeLayer = [[CAShapeLayer alloc] init];
shapeLayer.path = [UIBezierPath bezierPathWithRect:(CGRect){ 0,0,10,100 }].CGPath;
shapeLayer.backgroundColor = [[UIColor blueColor] colorWithAlphaComponent:0.6].CGColor;
shapeLayer.frame = (CGRect){60, 60, 100, 100};
[self.view.layer addSublayer:shapeLayer];
self.layer2 = shapeLayer;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint touchPoint = [(UITouch*)[touches anyObject] locationInView:self.view];
CALayer *touchedLayer = [self.view.layer.presentationLayer hitTest:touchPoint];
CALayer *originalLayer = [touchedLayer modelLayer];
for ( CAShapeLayer *layer in #[self.layer1, self.layer2])
{
if (![layer isKindOfClass:[CAShapeLayer class]]) { continue; }
CGPoint point = [layer convertPoint:touchPoint fromLayer:self.view.layer];
if (CGPathContainsPoint(layer.path, 0, point, 0))
{
NSLog(#"match found");
if (originalLayer == self.layer1) { NSLog(#"layer 1 touched"); }
if (originalLayer == self.layer2) { NSLog(#"layer 2 touched"); }
return;
}
}
}