objective-c – 具有贝塞尔曲线和恒定速度的CAKeyframeAnimation

2019年8月3日 142次阅读

我试图沿着包含一些贝塞尔曲线的CGPathRef动画图形,我希望动画从开始到结束具有平滑,恒定的速度.我遇到的是,每次碰到一个关键点时,动画就会缓慢进出.我尝试过使用不同的timingFunction和calculateMode设置,但我似乎无法找到合适的组合来完成工作.

这是我到目前为止所得到的：

-(void)animate
{
  CAKeyframeAnimation *posAnim = [CAKeyframeAnimation animationWithKeyPath:@"position"];
  posAnim.path = [self pathForAnimation];
  posAnim.duration = 12.0;
  posAnim.calculationMode = kCAAnimationPaced;
  posAnim.fillMode = kCAFillModeBoth;
  posAnim.removedOnCompletion = NO;
  posAnim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
  [image.layer addAnimation:posAnim forKey:@"posAnim"];
}

-(CGPathRef)pathForAnimation
{
  CGMutablePathRef path;
  CGPoint point;
  CGPoint controlPoint1;
  CGPoint controlPoint2;

  path = CGPathCreateMutable();
  point = CGPointMake(209.5f, 24.5f);
  CGPathMoveToPoint(path, NULL, point.x, point.y);

  point = CGPointMake(249.5f, 64.5f);
  controlPoint1 = CGPointMake(232.5f, 25.5f);
  controlPoint2 = CGPointMake(249.5f, 37.5f);
  CGPathAddCurveToPoint(path, NULL, controlPoint1.x, controlPoint1.y, controlPoint2.x, controlPoint2.y, point.x, point.y);

  point = CGPointMake(146.5f, 301.5f);
  controlPoint1 = CGPointMake(249.5f, 91.5f);
  controlPoint2 = CGPointMake(147.5f, 258.5f);
  CGPathAddCurveToPoint(path, NULL, controlPoint1.x, controlPoint1.y, controlPoint2.x, controlPoint2.y, point.x, point.y);

  point = CGPointMake(146.5f, 458.5f);
  controlPoint1 = CGPointMake(145.5f, 344.5f);
  controlPoint2 = CGPointMake(170.5f, 418.5f);
  CGPathAddCurveToPoint(path, NULL, controlPoint1.x, controlPoint1.y, controlPoint2.x, controlPoint2.y, point.x, point.y);

  point = CGPointMake(18.5f, 530.5f);
  controlPoint1 = CGPointMake(122.5f, 498.5f);
  controlPoint2 = CGPointMake(18.5f, 530.5f);
  CGPathAddCurveToPoint(path, NULL, controlPoint1.x, controlPoint1.y, controlPoint2.x, controlPoint2.y, point.x, point.y);

  return path;
}

为了它的价值,我尝试用直线替换曲线(使用CGPathAddLineToPoint),这给了我一个像我想要的恒定速度.但当然,如果可能,我宁愿拥有曲线.

我也尝试用timingFunctions数组替换timingFunction,但无济于事.

最佳答案 您是否尝试将关键帧动画的calculateMode属性设置为kCAAnimationCubicPaced？该属性专门用于使动画遵循整个曲线的恒定步调.

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