如何使图层保持CABasicAnimation的最终值

Question

请考虑以下动画：

CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
pathAnimation.duration = 1.0;
pathAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];
pathAnimation.removedOnCompletion = NO;
pathAnimation.delegate = self;

这将基本上为从一端到下一端的图层绘制动画。问题是，一旦动画完成，strokeEnd属性将重置为0（最初设置的位置）。如何使最终值“坚持”？

我试图在animationDidStop委托方法中更改它。这大部分都有效，但即使放入CATransaction以禁用动画，也会导致strokeEnd在0处短暂闪现。我也玩过additive和cumulative属性无济于事。有什么建议？

Answer 1

您只需将strokeEnd属性设置为其最终值！像这样：

// your current code (stripped of unnecessary stuff)

CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
pathAnimation.duration = 1.0;
pathAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];

// just add this to it:

theLayer.strokeEnd = 1;

// and now add the animation to theLayer

如果strokeEnd是隐式可动画的（因此该行本身会导致动画），我们将首先关闭隐式动画：

[CATransaction setDisableActions:YES];
theLayer.strokeEnd = 1;

请注意，你的pathAnimation.removedOnCompletion = NO;是错误的，另一个答案是kCAFillModeForwards。两者都是基于对Core Animation如何工作的误解。