CATransaction是即时的，忽略转换时间

Question

我不明白为什么这样的代码：

CALayer *viewLayer = [aView layer];
[CATransaction begin];
[CATransaction setValue:[NSNumber numberWithFloat:10.0f]
                 forKey:kCATransactionAnimationDuration];
viewLayer.position = CGPointMake(200.0f, 200.0f);
viewLayer.position = CGPointMake(320.0f, 480.0f);

[CATransaction commit];

移动视图，但移动不是动画(移动是即时的)。aView是UIView中的UIImageView。

Answer 1

对于与视图关联的层，将禁用隐式操作。视图始终是其自己层的代理，它实现-actionForKey:禁用隐式动画，仅在UIView动画块内添加动画。最好的办法就是直接使用显式的CABasicAnimations。假设您想要从第一个点到第二个点设置动画，您可以使用类似于

CALayer *layer = aView.layer;

layer.position = CGPointMake(320, 480); // final position
CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:@"position"];
anim.fromValue = [NSValue valueWithCGPoint:CGPointMake(200, 200)];
anim.toValue = [NSValue valueWithCGPoint:layer.position]; // I believe this line is optional, it should default to current position
[layer addAnimation:anim forKey:@"position"];