iOS Core Animation学习总结(2)--实现自定义图层

@interface CTLayer : CALayer

@end

@implementation CTLayer
-(void)drawInContext:(CGContextRef)ctx{
　　 //画一个圆
    CGContextSetRGBFillColor(ctx, 0, 0, 1, 1);
    CGContextAddEllipseInRect(ctx, CGRectMake(100, 100, 100, 100));
    CGContextFillPath(ctx);
}
@end

    CTLayer *layer = [CTLayer layer];
    layer.bounds = CGRectMake(0, 0, 300, 300);
    layer.anchorPoint = CGPointMake(0,0);
    [layer setNeedsDisplay];//显示图层
    [self.view.layer addSublayer:layer];

    CTLayer *layer = [CTLayer layer];
    layer.bounds = CGRectMake(0, 0, 300, 300);
    layer.anchorPoint = CGPointMake(0,0);
    layer.delegate = self; //指定代理，该代理可为任意类型
    [layer setNeedsDisplay];//显示layer
    [self.view.layer addSublayer:layer];

#pragma mark 代理方法
-(void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx{
    CGContextSetRGBFillColor(ctx, 0, 0, 1, 1);
    CGContextAddEllipseInRect(ctx, CGRectMake(100, 100, 100, 100));
    CGContextFillPath(ctx);
}