CAKeyframeAnimation不适用于子类

Question

我移动一个带动画的按钮，如果我在UIVIewController中使用它完全正常工作，如果我尝试使用这个动画继承UIView我看不到它，按钮出现在终点但是我不知道看它动了。 错误在哪里？

这是我的代码：

- (void) moveButton:(UIButton *)button fromPoint:(CGPoint)startPoint toPoint:(CGPoint)endPoint {

        CGMutablePathRef thePath = CGPathCreateMutable();
        CGPathMoveToPoint(thePath, NULL, startPoint.x, startPoint.y);

        NSMutableArray *timings = [NSMutableArray array];
        NSMutableArray *keytimes = [NSMutableArray array];

        // Start
        [timings addObject:[self getTiming:kCAMediaTimingFunctionEaseIn]];
        [keytimes addObject:[NSNumber numberWithFloat:0.0]];

        // Bounce
        [timings addObject:[self getTiming:kCAMediaTimingFunctionEaseIn]];
        [keytimes addObject:[NSNumber numberWithFloat:1.0]];

        CAKeyframeAnimation * animation;
        animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
        animation.fillMode = kCAFillModeForwards;
        animation.removedOnCompletion = NO;
        animation.duration = 2;
        animation.path = thePath;
        animation.timingFunctions = timings;
        animation.keyTimes = keytimes;

        [[button layer] addAnimation:animation forKey:nil];
        [[button layer] setPosition:CGPointMake(endPoint.x,endPoint.y)];
    }