Question

我有一个基本动画，只是旋转图像，我正在使用Core Animation。在viewWillAppear方法中，我创建了动画：

gearRotate = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
gearRotate.repeatCount = HUGE_VALF;
gearRotate.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
gearRotate.duration = 2;
gearRotate.fromValue = 0;
gearRotate.toValue = [NSNumber numberWithFloat:(360*M_PI)/180];
[gearButton.imageView.layer addAnimation:gearRotate forKey:@"transform.rotation"];


[self stopGear];

我最初调用stopGear来暂停动画。我确实在viewDidLoad中有这个代码。无论如何，当动画被调用时，它可以正常工作：

-(void)startGear {
CFTimeInterval pausedTime = [gearButton.imageView.layer timeOffset];
gearButton.imageView.layer.speed = 1.0;
gearButton.imageView.layer.timeOffset = 0.0;
gearButton.imageView.layer.beginTime = 0.0;
CFTimeInterval timeSincePause = [gearButton.imageView.layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
gearButton.imageView.layer.beginTime = timeSincePause;

}

这种暂停方法也可以正常工作：

-(void)stopGear {
CFTimeInterval pausedTime = [gearButton.imageView.layer convertTime:CACurrentMediaTime() fromLayer:nil];
gearButton.imageView.layer.speed = 0.0;
gearButton.imageView.layer.timeOffset = pausedTime;

}

然而，如果我转到另一个视图然后回到主视图，这一切都会失败。该应用程序运行正常，但如果我去过另一个视图，动画将永远不会运行。

这就是为什么我最初将此代码移动到viewWillAppear，认为我需要重新创建动画，但没有bean。有什么想法吗？

感谢。

Answer 1

好的，所以我通过重新思考动画是如何工作的来解决这个问题。我现在只是想在每次运行时创建动画：

-(void)startGear {
    gearRotate = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
    gearRotate.repeatCount = HUGE_VALF;
    gearRotate.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    gearRotate.duration = 2;
    gearRotate.fromValue = 0;
    gearRotate.toValue = [NSNumber numberWithFloat:(360*M_PI)/180];
    [[gearButton.imageView layer] addAnimation:gearRotate forKey:@"transform.rotation"];

}

当我想暂停它时，我只是删除它：

-(void)stopGear {
    [[gearButton.imageView layer] removeAnimationForKey:@"transform.rotation"];

}

我目前不确定这是否是Apple的首选方法，但它能够稳定运行。

Answer 2

您可以使用以下方法，而不是使用gearRotate.repeatCount = HUGE_VALF;，以便在对另一个视图控制器执行segue后保持动画运行：

-(void)startGear {
    [[gearButton.imageView layer] removeAnimationForKey:@"transform.rotation"];
    gearRotate = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
    gearRotate.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    gearRotate.duration = 2;
    gearRotate.fromValue = 0;
    gearRotate.toValue = [NSNumber numberWithFloat:(360*M_PI)/180];
    [[gearButton.imageView layer] addAnimation:gearRotate forKey:@"transform.rotation"];
    [self performSelector:@selector(startGear) withObject:nil afterDelay:gearRotate.duration];
}

在segue / view转换后，iOS Core Animation失败

2 个答案: