如何围绕任意点旋转对象？ [英] How to rotate an object around a arbitrary point?

问题描述

我想围绕任意点以圆形方式旋转UILabel，而不是直线。这是我的代码。最后一点是完美的，但它通过一个直线在初始和结束点之间。

I want to rotate an UILabel around an arbitrary point in a circular manner, not a straight line. This is my code.The final point is perfect but it goes through a straight line between the initial and the end points.

- (void)rotateText:(UILabel *)label duration:(NSTimeInterval)duration degrees:(CGFloat)degrees {
    /* Setup the animation */
    [UILabel beginAnimations:nil context:NULL];
    [UILabel setAnimationDuration:duration];


    CGPoint rotationPoint = CGPointMake(160, 236);
    CGPoint transportPoint = CGPointMake(rotationPoint.x - label.center.x, rotationPoint.y - label.center.y);

    CGAffineTransform t1 = CGAffineTransformTranslate(label.transform, transportPoint.x, -transportPoint.y);
    CGAffineTransform t2 = CGAffineTransformRotate(label.transform,DEGREES_TO_RADIANS(degrees));
    CGAffineTransform t3 = CGAffineTransformTranslate(label.transform, -transportPoint.x, +transportPoint.y);

    CGAffineTransform t4 = CGAffineTransformConcat(CGAffineTransformConcat(t1, t2), t3);
    label.transform = t4;   

    /* Commit the changes */
    [UILabel commitAnimations];

}

推荐答案

发布我的解决方案作为答案。它工作正常接受它没有旧解决方案的曲线动画（UIViewAnimationCurveEaseOut），但我可以排序。

I decided to post my solution as an answer. It works fine accept it doesn't have the old solutions's curve animations (UIViewAnimationCurveEaseOut), but I can sort that out.

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

- (void)rotateText:(UILabel *)label duration:(NSTimeInterval)duration degrees:(CGFloat)degrees {
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddArc(path,nil, 160, 236, 100, DEGREES_TO_RADIANS(0), DEGREES_TO_RADIANS(degrees), YES);

    CAKeyframeAnimation *theAnimation;

    // animation object for the key path
    theAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    theAnimation.path=path;
    CGPathRelease(path);

    // set the animation properties
    theAnimation.duration=duration;
    theAnimation.removedOnCompletion = NO; 
    theAnimation.autoreverses = NO;
    theAnimation.rotationMode = kCAAnimationRotateAutoReverse;
    theAnimation.fillMode = kCAFillModeForwards;

    [label.layer addAnimation:theAnimation forKey:@"position"]; 
}

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