基本关键帧动画（旋转） [英] Basic keyframe animation (rotation)

问题描述

我正在尝试创建一个非常简单的关键帧动画，其中图形通过给定的中点从一个角度旋转到另一个角度。

I'm trying to create a very simple keyframe animation, whereby a graphic Rotates from one angle to another, through a given midpoint.

（目的是能够通过 OBTUSE 角度大于180度的弧度设置旋转动画，而不是让动画'作弊'并走最短的路线，即通过相反的，ACUTE 更小的角度 - 这可能发生在只有一个[即目标]关键帧的时候。为了走'长'的路，我假设我需要一个额外的关键帧，沿着所需的弧。）

(The purpose is to be able to animate rotation through an OBTUSE angle of arc GREATER THAN 180 DEGREES, rather than having the animation 'cheat' and go the shortest route, i.e., via the opposite , ACUTE smaller angle -- which can happen when there's only one [i.e, destination] keyframe. To go the 'long' way around, I assume I need an extra keyframe midway through, along the desired arc.)

这是我到目前为止所得到的（它确实得到了图形）到达所需的旋转，通过最锐角）：

Here's what I've got so far (which does get the graphic to the desired rotation, via the most acute angle):

#define DEGREES_TO_RADIANS(__ANGLE__) ((__ANGLE__) / 180.0 * M_PI)

...

[UIView beginAnimations:nil context:nil];
CGAffineTransform cgCTM = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(desiredEndingAngle));
[UIView setAnimationDuration:0.5];
graphic.transform = cgCTM;
[UIView commitAnimations];

根据我的理解，我不是要沿着路径寻找动画（因为那是翻译，而不是轮换）...

As I understand it, I’m not looking for animation along a Path (since that’s for Translation, rather than Rotation) ...

无论如何，任何帮助都会非常感激！提前谢谢。

Anyway, any help would be VERY much appreciated! Thanks in advance.

推荐答案

想想我已经知道了。

这里的代码（在本例中）完全旋转270度（1.5 * pi弧度），包括可以进一步定制的各种参数：

Here’s code which does (in this example) a full 270 DEGREE rotation (1.5*pi radians), including various parameters that can be customized further:

CALayer *layer = rotatingImage.layer;
CAKeyframeAnimation *animation;
animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
animation.duration = 0.5f;
animation.cumulative = YES;
animation.repeatCount = 1;
animation.values = [NSArray arrayWithObjects:       // i.e., Rotation values for the 3 keyframes, in RADIANS
      [NSNumber numberWithFloat:0.0 * M_PI], 
      [NSNumber numberWithFloat:0.75 * M_PI], 
      [NSNumber numberWithFloat:1.5 * M_PI], nil]; 
animation.keyTimes = [NSArray arrayWithObjects:     // Relative timing values for the 3 keyframes
      [NSNumber numberWithFloat:0], 
      [NSNumber numberWithFloat:.5], 
      [NSNumber numberWithFloat:1.0], nil]; 
animation.timingFunctions = [NSArray arrayWithObjects:
      [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn],    // from keyframe 1 to keyframe 2
      [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut], nil]; // from keyframe 2 to keyframe 3
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;

[layer addAnimation:animation forKey:nil];

谢谢！

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