CALayerDelegate的实现(IOS)

by 伍雪颖
[img]http://img.blog.csdn.net/20150103225723765?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvcmFpbmxlc3Zpbw==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center
- (void)viewDidLoad {
    [super viewDidLoad];
    CALayer *blueLayer = [CALayer layer];
    blueLayer.frame = CGRectMake(50, 50, 100, 100);
    blueLayer.backgroundColor = [UIColor blueColor].CGColor;
    [self.layerView.layer addSublayer:blueLayer];
   
    blueLayer.delegate = self;
    blueLayer.contentsScale = [UIScreen mainScreen].scale;
   
    [blueLayer display];
}
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
    CGContextSetLineWidth(ctx, 10);
    CGContextSetStrokeColorWithColor(ctx, [UIColor redColor].CGColor);
    CGContextStrokeEllipseInRect(ctx, layer.bounds);
}