Layer Geometry - iOS Core Animation - page 43

Listing 3.4 Determining the Touched Layer Using containsPoint:
@interface ViewController ()
@property ( nonatomic , weak ) IBOutlet UIView *layerView;
@property ( nonatomic , weak ) CALayer *blueLayer;
@end
@implementation ViewController
- ( void )viewDidLoad
{
[ super viewDidLoad ];
//create sublayer
self .blueLayer = [ CALayer layer ];
self .blueLayer. frame = CGRectMake ( 50.0f , 50.0f , 100.0f , 100.0f );
self .blueLayer. backgroundColor = [ UIColor blueColor ]. CGColor ;
//add it to our view
[ self .layerView. layer addSublayer : self .blueLayer];
}
- ( void )touchesBegan:( NSSet *)touches withEvent:( UIEvent *)event
{
//get touch position relative to main view
CGPoint point = [[touches anyObject ] locationInView : self . view ];
//convert point to the white layer's coordinates
point = [ self .layerView. layer convertPoint :point
fromLayer : self .view. layer ];
//get layer using containsPoint:
if ([ self .layerView. layer containsPoint :point])
{
//convert point to blueLayer's coordinates
point = [ self .blueLayer convertPoint :point
fromLayer : self .layerView. layer ];
if ([ self .blueLayer containsPoint :point])
{
[[[ UIAlertView alloc ] initWithTitle : @"Inside Blue Layer"
message : nil
delegate : nil
cancelButtonTitle : @"OK"