我正在尝试实现一个翻转动画，以便在 iPhone 应用程序等棋盘游戏中使用。动画应该看起来像一个旋转并改变其背部颜色的游戏块（有点像黑白棋）。我已经设法创建了一个动画，它围绕其正交轴翻转作品，但是当我尝试通过改变围绕 z 轴的旋转来围绕对角轴翻转它时，实际图像也会旋转（不足为奇）。相反，我想围绕对角轴“按原样”旋转图像。
我试图改变layer.sublayerTransform，但没有成功。
这是我目前的实现。它通过一个技巧来解决在动画结束时获取镜像图像的问题。解决方案是不实际将图层旋转 180 度，而是将其旋转 90 度，更改图像，然后将其旋转回来。
最终版本：根据 Lorenzos 的建议创建离散键控动画并计算每一帧的变换矩阵。此版本尝试根据图层大小估算所需的“引导”帧数，然后使用线性键控动画。此版本以任意角度旋转，因此围绕对角线旋转使用 45 度角。
示例用法：
[someclass flipLayer:layer image:image angle:M_PI/4]
执行：
- (void)animationDidStop:(CAAnimationGroup *)animation
finished:(BOOL)finished {
CALayer *layer = [animation valueForKey:@"layer"];
if([[animation valueForKey:@"name"] isEqual:@"fadeAnimation"]) {
/* code for another animation */
} else if([[animation valueForKey:@"name"] isEqual:@"flipAnimation"]) {
layer.contents = [animation valueForKey:@"image"];
}
[layer removeAllAnimations];
}
- (void)flipLayer:(CALayer *)layer
image:(CGImageRef)image
angle:(float)angle {
const float duration = 0.5f;
CAKeyframeAnimation *rotate = [CAKeyframeAnimation
animationWithKeyPath:@"transform"];
NSMutableArray *values = [[[NSMutableArray alloc] init] autorelease];
NSMutableArray *times = [[[NSMutableArray alloc] init] autorelease];
/* bigger layers need more "guiding" values */
int frames = MAX(layer.bounds.size.width, layer.bounds.size.height) / 2;
int i;
for (i = 0; i < frames; i++) {
/* create a scale value going from 1.0 to 0.1 to 1.0 */
float scale = MAX(fabs((float)(frames-i*2)/(frames - 1)), 0.1);
CGAffineTransform t1, t2, t3;
t1 = CGAffineTransformMakeRotation(angle);
t2 = CGAffineTransformScale(t1, scale, 1.0f);
t3 = CGAffineTransformRotate(t2, -angle);
CATransform3D trans = CATransform3DMakeAffineTransform(t3);
[values addObject:[NSValue valueWithCATransform3D:trans]];
[times addObject:[NSNumber numberWithFloat:(float)i/(frames - 1)]];
}
rotate.values = values;
rotate.keyTimes = times;
rotate.duration = duration;
rotate.calculationMode = kCAAnimationLinear;
CAKeyframeAnimation *replace = [CAKeyframeAnimation
animationWithKeyPath:@"contents"];
replace.duration = duration / 2;
replace.beginTime = duration / 2;
replace.values = [NSArray arrayWithObjects:(id)image, nil];
replace.keyTimes = [NSArray arrayWithObjects:
[NSNumber numberWithDouble:0.0f], nil];
replace.calculationMode = kCAAnimationDiscrete;
CAAnimationGroup *group = [CAAnimationGroup animation];
group.duration = duration;
group.timingFunction = [CAMediaTimingFunction
functionWithName:kCAMediaTimingFunctionLinear];
group.animations = [NSArray arrayWithObjects:rotate, replace, nil];
group.delegate = self;
group.removedOnCompletion = NO;
group.fillMode = kCAFillModeForwards;
[group setValue:@"flipAnimation" forKey:@"name"];
[group setValue:layer forKey:@"layer"];
[group setValue:(id)image forKey:@"image"];
[layer addAnimation:group forKey:nil];
}
原始代码：
+ (void)flipLayer:(CALayer *)layer
toImage:(CGImageRef)image
withAngle:(double)angle {
const float duration = 0.5f;
CAKeyframeAnimation *diag = [CAKeyframeAnimation
animationWithKeyPath:@"transform.rotation.z"];
diag.duration = duration;
diag.values = [NSArray arrayWithObjects:
[NSNumber numberWithDouble:angle],
[NSNumber numberWithDouble:0.0f],
nil];
diag.keyTimes = [NSArray arrayWithObjects:
[NSNumber numberWithDouble:0.0f],
[NSNumber numberWithDouble:1.0f],
nil];
diag.calculationMode = kCAAnimationDiscrete;
CAKeyframeAnimation *flip = [CAKeyframeAnimation
animationWithKeyPath:@"transform.rotation.y"];
flip.duration = duration;
flip.values = [NSArray arrayWithObjects:
[NSNumber numberWithDouble:0.0f],
[NSNumber numberWithDouble:M_PI / 2],
[NSNumber numberWithDouble:0.0f],
nil];
flip.keyTimes = [NSArray arrayWithObjects:
[NSNumber numberWithDouble:0.0f],
[NSNumber numberWithDouble:0.5f],
[NSNumber numberWithDouble:1.0f],
nil];
flip.calculationMode = kCAAnimationLinear;
CAKeyframeAnimation *replace = [CAKeyframeAnimation
animationWithKeyPath:@"contents"];
replace.duration = duration / 2;
replace.beginTime = duration / 2;
replace.values = [NSArray arrayWithObjects:(id)image, nil];
replace.keyTimes = [NSArray arrayWithObjects:
[NSNumber numberWithDouble:0.0f], nil];
replace.calculationMode = kCAAnimationDiscrete;
CAAnimationGroup *group = [CAAnimationGroup animation];
group.removedOnCompletion = NO;
group.duration = duration;
group.timingFunction = [CAMediaTimingFunction
functionWithName:kCAMediaTimingFunctionLinear];
group.animations = [NSArray arrayWithObjects:diag, flip, replace, nil];
group.fillMode = kCAFillModeForwards;
[layer addAnimation:group forKey:nil];
}
