模仿UIAlertView Bounce？

Question

什么是模仿iPhone上UIAlertView的弹跳动画的最佳方式？这有一些内置机制吗？ UIAlertView本身不能满足我的需求。

我查看了动画曲线，但据我所知，他们提供的只有easyIn，easeOut和linear。

Answer 1

UIAlertView使用更复杂的动画：

• 规模大于100％
• 缩小至小于100％
• 缩放至100％

以下是使用CAKeyFrameAnimation：

的实现

view.alpha = 0;
[UIView animateWithDuration:0.1 animations:^{view.alpha = 1.0;}];

CAKeyframeAnimation *bounceAnimation = [CAKeyframeAnimation animationWithKeyPath:@"transform.scale"];
bounceAnimation.values = @[@0.01f, @1.1f, @0.8f, @1.0f];
bounceAnimation.keyTimes = @[@0.0f, @0.5f, @0.75f, @1.0f];
bounceAnimation.duration = 0.4;
[view.layer addAnimation:bounceAnimation forKey:@"bounce"];

Answer 2

我调查了如何通过调动UIAlertView将动画添加到-[CALayer addAnimation:forKey:]的图层中。以下是我为其执行的缩放变换动画获得的值：

0.01f -> 1.10f -> 0.90f -> 1.00f

持续时间

0.2s, 0.1s, 0.1s。

所有动画都使用缓入/缓出计时功能。这是一个CAKeyframeAnimation，它封装了这个逻辑：

CAKeyframeAnimation *bounceAnimation = [CAKeyframeAnimation animationWithKeyPath:@"transform"];
bounceAnimation.fillMode = kCAFillModeBoth;
bounceAnimation.removedOnCompletion = YES;
bounceAnimation.duration = 0.4;
bounceAnimation.values = @[
    [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.01f, 0.01f, 0.01f)],
    [NSValue valueWithCATransform3D:CATransform3DMakeScale(1.1f, 1.1f, 1.1f)],
    [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.9f, 0.9f, 0.9f)],
    [NSValue valueWithCATransform3D:CATransform3DIdentity]];
bounceAnimation.keyTimes = @[@0.0f, @0.5f, @0.75f, @1.0f];
bounceAnimation.timingFunctions = @[
    [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],
    [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],
    [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];

我相信UIAlertView在变换动画的总持续时间（0.0f）内也会执行从1.0f到0.4的简单不透明度动画。

Answer 3

你可以使用2个动画，一个弹出非常大，另一个重新缩放回正常大小。

（这是UIAlertView内部使用的方法。）

或者，您可以使用较低级CAAnimation并使用+[CAMediaTimingFunction functionWithControlPoints::::]制作自己的曲线。

Answer 4

以下是我为我正在开发的应用做的事情。当你按下视图时，我想要的效果就是弹跳。尝试使用适合您口味的值和所需的效果速度。

- (void) bounceView:(UIView*)bouncer
{
    // set duration to whatever you want
    float duration = 1.25;
    // use a consistent frame rate for smooth animation.
    // experiment to your taste
    float numSteps = 15 * duration;

    // scale the image up and down, halving the distance each time
    [UIView animateKeyframesWithDuration:duration
                                   delay:0
                                 options:UIViewKeyframeAnimationOptionCalculationModeCubic
                              animations:^{
                                  float minScale = 0.50f; // minimum amount of shrink
                                  float maxScale = 1.75f; // maximum amount of grow
                                  for(int i = 0; i< numSteps*2; i+=2)
                                  {
                                      // bounce down
                                      [UIView addKeyframeWithRelativeStartTime:duration/numSteps * i
                                                              relativeDuration:duration/numSteps
                                                                    animations:^{
                                                                        bouncer.layer.transform = CATransform3DMakeScale(minScale, minScale, 1);
                                                                    }];
                                      // bounce up
                                      [UIView addKeyframeWithRelativeStartTime:duration/numSteps * (i+1)
                                                              relativeDuration:duration/numSteps
                                                                    animations:^{
                                                                        bouncer.layer.transform = CATransform3DMakeScale(maxScale, maxScale, 1);
                                                                    }];

                                      // cut min scale halfway to identity
                                      minScale = minScale + (1.0f - minScale) / 2.0f;
                                      // cut max scale halfway to identity
                                      maxScale = 1.0f + (maxScale - 1.0f) / 2.0f;
                                  }
                              } completion:^(BOOL finished) {
                                  // quickly smooth out any rounding errors
                                  [UIView animateWithDuration:0.5*duration/numSteps animations:^{
                                      bouncer.layer.transform = CATransform3DIdentity;
                                  }];
                              }];
}