Question

我正在将CABasicAnimation应用于动画效果良好的图层的位置属性，但是在动画完成后它会回到原始位置，如何避免这种情况并使图像仅保持在动画位置？

Answer 1

有几种不同的方法可以解决这个问题。我最喜欢的是在动画结束时设置对象，并使用fromValue而不是toValue来创建动画。您还可以设置fromValue和toValue来创建此效果。即

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"position"];
animation.duration = 1.0;
animation.fromValue = [NSValue valueWithCGPoint:startPoint];
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];

viewToAnimate.center = endPoint;
[viewToAnimate.layer addAnimation:animation forKey:@"slide"];

另一种方法是将自己设置为委托并实施：

-(void)animationDidStop:(id)sender finished:(BOOL)finished {
     viewToAnimate.center = endPoint;
}

Answer 2

您需要设置最终位置。如果您只使用动画fromValue和toValue，它将快速回到原始起点。动画在“播放”时使用视图/图层的副本，然后动画将在完成时显示原始视图/图层。

如果你没有明确地设置它，它会显示为快照，即使视图/图层从未真正移动过。

startPoint和endPoint是CGPoints，myView是动画的UIView。

    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"position"];
    animation.duration = .3;
    animation.fromValue = [NSValue valueWithCGPoint:startPoint];
    animation.toValue = [NSValue valueWithCGPoint:endPoint];
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    [myView.layer addAnimation:animation forKey:@"position"];   
    myView.layer.position = endPoint;   // Must set end position, otherwise it jumps back

Answer 3

要在动画结束时设置对象，只需编写如下代码

#import <QuartzCore/QuartzCore.h>

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"position"];
animation.duration = 1.0;
animation.fromValue = [NSValue valueWithCGPoint:startPoint];
animation.timingFunction = [CAMediaTimingFunction functionWithName:easing];
animation.fillMode = kCAFillModeForwards;  // This line will stop the animation at the end position of animation
animation.autoreverses = NO;

viewToAnimate.center = endPoint;
[viewToAnimate.layer addAnimation:animation forKey:@"slide"];

Answer 4

如果要保留最终值，可以将removedOnCompletion设置为NO。并且不要忘记设置fillMode。

animation.fillMode = kCAFillModeForwards;  //The receiver remains visible in its final state when the animation is completed.
animation.removedOnCompletion = NO;

Answer 5

如果您查看addAnimation：forKey：的文档，则会显示“通常会隐式调用此方法”。换句话说，你不应该直接调用它。您实际上打算执行以下操作，这比设置from和to值更容易，只需直接在图层上设置值：

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
animation.duration = .3;

myLayer.actions = @{@"opacity": animation};
myLayer.opacity = 0;

这会将图层淡化为零不透明度。

动画完成后，CABasicAnimation不会更改其位置属性

5 个答案: