将Box2D物理应用于UIView vs. CALayer

Question

我用这个优秀的教程启动了一个我正在研究涉及物理学的小项目:

http://www.cocoanetics.com/2010/05/physics-101-uikit-app-with-box2d-for-gravity/

基本上,它创造了一个世界,并将B2D的物理特性应用于您拥有的任何视图.很简单,它的工作原理.但是,我尝试使用CALayers应用相同的逻辑,即,我以编程方式创建图层,将它们添加到主view.layer并尝试为它们设置动画.

用于创建图层的示例代码:

CALayer *layer = [CALayer layer];
layer.backgroundColor = [UIColor blackColor].CGColor;
layer.frame = CGRectMake(50, 100, 30, 30);
layer.name = @"square";
[self.view.layer addSublayer:layer];

并且在自动收报机中应用物理:

CALayer *oneLayer = (CALayer *)b->GetUserData();
// y Position subtracted because of flipped coordinate system
CGPoint newCenter = CGPointMake(b->GetPosition().x * PTM_RATIO, self.view.bounds.size.height - b->GetPosition().y * PTM_RATIO);
oneLayer.position = newCenter;
CGAffineTransform transform = CGAffineTransformMakeRotation(- b->GetAngle());
oneLayer.affineTransform = transform;

请注意,我将仿射变换调用调整为CALayer类.

我检查并仔细检查了变量,数字似乎匹配.我得到的是来自CALayer动画的奇怪反弹,以及来自UIView的完美动画.有没有经验丰富的Box2D和UIKit来回答为什么会发生这种情况？

Answer 1

不像UIViews,CALayers有内置的隐式动画.每次更改动画属性的值时,都会引入短动画.您必须将代码包装CATransaction并禁用操作以消除此效果:

[CATransaction begin];
[CATransaction setDisableActions:YES]; // implicit animations get disabled

CALayer *oneLayer = (CALayer *)b->GetUserData();
// y Position subtracted because of flipped coordinate system
CGPoint newCenter = CGPointMake(b->GetPosition().x * PTM_RATIO, self.view.bounds.size.height - b->GetPosition().y * PTM_RATIO);
oneLayer.position = newCenter;
CGAffineTransform transform = CGAffineTransformMakeRotation(- b->GetAngle());
oneLayer.affineTransform = transform;

[CATransaction commit];