CALayer 自定义属性绘制动画

创建CircleLayer继承CALayer，添加新属性angle。

@interfaceCircleLayer :CALayer
@property(nonatomic,assign)CGFloatangle;

@end

覆盖父类方法，添加新的属性动画键值，返回YES表示给定的属性发生变化时导致layer的内容重绘

+ (BOOL)needsDisplayForKey:(NSString*)key
{
   if([keyisEqualToString:@"angle"]) {
       returnYES;
    }
   return[superneedsDisplayForKey:key];

}

代码绘制部分

- (void)drawInContext:(CGContextRef)ctx
{
    CGFloat lineWidth = 3.0f;
    CGPoint centerPoint = CGPointMake(CGRectGetWidth(self.bounds)/2, CGRectGetHeight(self.bounds)/2);
   
    CGContextBeginPath(ctx);
    CGContextAddArc(ctx, centerPoint.x, centerPoint.y, CGRectGetWidth(self.bounds)/2 -lineWidth/2, 0.0f, self.angle, 0);
    CGContextEndPage(ctx);
   
    CGContextSetStrokeColorWithColor(ctx, [UIColorredColor].CGColor);
    CGContextSetLineWidth(ctx, lineWidth);
    CGContextStrokePath(ctx);

}

创建CABasicAnimation动画

CircleLayer *layer = [CircleLayer layer];

layer.frame = CGRectMake(10, 100, 40, 40);

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"angle"];

animation.fromValue = @(0.0f);

animation.toValue = @(2*M_PI);

animation.repeatCount = MAXFLOAT;

animation.duration = 3.0f;

[layer addAnimation:animation forKey:@"angle_key"];