问题
Consider the following animation:
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;
This will essentially animate the drawing of the layer from one end to the next. The problem is that once the animation completes, the strokeEnd property resets back to 0 (where it was initially set). How do I make the final value "stick"?
I have attempted to change this in the animationDidStop delegate method. This mostly works, but can cause a flash of strokeEnd at 0 briefly, even when put inside a CATransaction to disable animations. I have also played with the additive and cumulative properties to no avail. Any suggestions?
回答1:
You simply set the strokeEnd property to its final value yourself! Like this:
// 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
If strokeEnd were implicitly animatable (so that that line would itself cause animation) we would turn off implicit animation first:
[CATransaction setDisableActions:YES];
theLayer.strokeEnd = 1;
Note that your pathAnimation.removedOnCompletion = NO; is wrong, and so is the other answer's kCAFillModeForwards. Both are based on misunderstandings of how Core Animation works.
来源：https://stackoverflow.com/questions/16326623/how-do-i-make-a-layer-maintain-the-final-value-of-a-cabasicanimation