CALayer实现点击屏幕放大或者缩小的一个圆

#import "ViewController.h"
#define WIDTH 50
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self drawMyLayer];
}
-(void)drawMyLayer
{
    CGSize size=[UIScreen mainScreen].bounds.size;
    
    CALayer *layer=[[CALayer alloc]init];
    layer.backgroundColor=[UIColor colorWithRed:0 green:146/255.0 blue:1.0 alpha:1.0].CGColor;
    layer.position=CGPointMake(size.width/2, size.height/2);
    layer.bounds=CGRectMake(0, 0, WIDTH, WIDTH);
    layer.cornerRadius=WIDTH/2;
    layer.shadowColor=[UIColor grayColor].CGColor;
    layer.shadowOffset=CGSizeMake(2, 2);
    layer.shadowOpacity=0.9;
    [self.view.layer addSublayer:layer];
    
    
    
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch=[touches anyObject];
    CALayer *layer=self.view.layer.sublayers[0];
    CGFloat width=layer.bounds.size.width;
    if (width==WIDTH) {
        width=WIDTH *4;
    }
    else
    {
        width=WIDTH;
    }
    layer.bounds=CGRectMake(0, 0, width, width);
    layer.position=[touch locationInView:self.view];
    layer.cornerRadius=width/2;
     [self.view.layer addSublayer:layer];
}
@end