看起来碰撞行为不像.ellipse 类型，当视图完全位于彼此之上时。
运行您的代码几次会产生不同的结果（如预期的那样）...有时，所有 5 个视图最终都在一个完整的垂直堆栈中，有时它以一些重叠结束，而其他时候（等待几秒钟后） ) 视图以可见的一对夫妇和其他方式在视图底部下方 - 我已经看到它们的 y 位置达到 > 40,000。
我对你的代码做了一些修改，看看发生了什么...
我添加了更多视图，并为每个视图提供了一个显示椭圆边界的形状层。
然后，我没有从相同的位置开始，而是创建了几个“行”，所以它看起来像这样：
然后，每次点击时，我都会重置原始位置并在椭圆和矩形之间切换UIDynamicItemCollisionBoundsType，然后然后再次调用addAnimatorAndBehaviors()。
这是在示例 .ellipse 运行时的样子：
在示例.rectangle 上运行：
正如我们所见，.ellipse 边界正在被使用。
这是我用来玩这个的代码：
class CustomContainerView: UIView {
var useEllipse: Bool = false
override public var collisionBoundsType: UIDynamicItemCollisionBoundsType {
return useEllipse ? .ellipse : .rectangle
}
}
class ViewController: UIViewController {
var arr = [CustomContainerView]()
var animator: UIDynamicAnimator!
var gravity: UIGravityBehavior!
var collider: UICollisionBehavior!
var bouncingBehavior : UIDynamicItemBehavior!
let infoLabel = UILabel()
override func viewDidLoad() {
super.viewDidLoad()
addSubViews()
// add info label
infoLabel.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(infoLabel)
infoLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
infoLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
// add a tap recognizer to start the Animator Behaviors
let t = UITapGestureRecognizer(target: self, action: #selector(gotTap(_:)))
view.addGestureRecognizer(t)
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
positionViews()
}
func positionViews() -> Void {
// let's make rows of the views,
// instead of starting with them all on top of each other
// we'll do 3-views over 2-views
let w = arr[0].frame.width * 1.1
let h = arr[0].frame.height * 1.1
var x: CGFloat = 0
var y: CGFloat = 0
var idx: Int = 0
y = h
while idx < arr.count {
x = view.center.x - w
for _ in 1...3 {
if idx < arr.count {
arr[idx].center = CGPoint(x: x, y: y)
}
x += w
idx += 1
}
y += h
x = view.center.x - w * 0.5
for _ in 1...2 {
if idx < arr.count {
arr[idx].center = CGPoint(x: x, y: y)
}
x += w
idx += 1
}
y += h
}
}
@objc func gotTap(_ g: UIGestureRecognizer) -> Void {
positionViews()
arr.forEach { v in
v.useEllipse.toggle()
}
infoLabel.text = arr[0].useEllipse ? "Ellipse" : "Rectangle"
addAnimatorAndBehaviors()
}
func addAnimatorAndBehaviors() {
animator = UIDynamicAnimator(referenceView: self.view)
gravity = UIGravityBehavior(items: arr)
animator.addBehavior(gravity)
collider = UICollisionBehavior(items: arr)
collider.translatesReferenceBoundsIntoBoundary = true
animator.addBehavior(collider)
bouncingBehavior = UIDynamicItemBehavior(items: arr)
bouncingBehavior.elasticity = 0.05
animator.addBehavior(bouncingBehavior)
}
func addSubViews() {
let clrs: [UIColor] = [
.red, .green, .blue,
.purple, .orange,
.cyan, .yellow, .magenta,
.systemTeal, .systemGreen,
]
clrs.forEach { c in
let v = createContainerView(with: c)
view.addSubview(v)
arr.append(v)
}
}
func createContainerView(with color: UIColor) -> CustomContainerView {
let containerView = CustomContainerView()
containerView.backgroundColor = UIColor.brown.withAlphaComponent(0.2)
let size = CGSize(width: 50, height: 50)
containerView.frame.size = size
view.addSubview(containerView)
let roundImageView = UIImageView()
roundImageView.translatesAutoresizingMaskIntoConstraints = false
roundImageView.backgroundColor = color
containerView.addSubview(roundImageView)
roundImageView.topAnchor.constraint(equalTo: containerView.topAnchor, constant: 10).isActive = true
roundImageView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor, constant: 10).isActive = true
roundImageView.trailingAnchor.constraint(equalTo: containerView.trailingAnchor, constant: -10).isActive = true
roundImageView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor, constant: -10).isActive = true
roundImageView.layer.masksToBounds = true
roundImageView.layoutIfNeeded()
roundImageView.layer.cornerRadius = roundImageView.frame.height / 2
roundImageView.layer.borderWidth = 1
roundImageView.layer.borderColor = UIColor.white.cgColor
// let's add a CAShapeLayer to show the ellipse bounds
let c = CAShapeLayer()
c.fillColor = UIColor.clear.cgColor
c.lineWidth = 1
c.strokeColor = UIColor.black.cgColor
c.path = UIBezierPath(ovalIn: CGRect(origin: .zero, size: size)).cgPath
containerView.layer.addSublayer(c)
return containerView
}
}
编辑
将positionViews() 中的while 循环更改为此...点击重置并多次运行动画，看看当所有视图从同一帧开始时会发生什么：
while idx < arr.count {
x = view.center.x - w
arr[idx].center = CGPoint(x: x, y: y)
idx += 1
}
然后，使用这个 while 循环，我们从相同的 x 位置开始视图，但增加每个视图的 y 位置（仅增加0.1 点）：
while idx < arr.count {
x = view.center.x - w
// increment the y position for each view -- just a tad
y += 0.1
arr[idx].center = CGPoint(x: x, y: y)
idx += 1
}
另一个编辑
值得注意的是，椭圆碰撞边界是圆形（1:1 ratio）这一事实也会影响事物。
如果我们稍微改变一下视图框架的大小，我们会得到非常不同的结果。
试试看：
let size = CGSize(width: 50.1, height: 50)
并从完全相同的中心点开始：
while idx < arr.count {
x = view.center.x - w
arr[idx].center = CGPoint(x: x, y: y)
idx += 1
}
您会立即看到视图展开。
再编辑一次 - 帮助可视化差异
这是另一个示例 - 这一次，我为视图编号并设置了一个“每 1/10 秒”计时器，以使用每个视图的当前中心更新标签。
还添加了分段控件以选择 collisionBoundsType 并将视图完全重叠在彼此之上或稍微偏移它们：
class CustomContainerView: UIView {
var useEllipse: Bool = false
override public var collisionBoundsType: UIDynamicItemCollisionBoundsType {
return useEllipse ? .ellipse : .rectangle
}
}
// extension to left-pad a string up-to length
extension RangeReplaceableCollection where Self: StringProtocol {
func paddingToLeft(upTo length: Int, using element: Element = " ") -> SubSequence {
return repeatElement(element, count: Swift.max(0, length-count)) + suffix(Swift.max(count, count-length))
}
}
class CollisionVC: UIViewController {
var arr = [CustomContainerView]()
var animator: UIDynamicAnimator!
var gravity: UIGravityBehavior!
var collider: UICollisionBehavior!
var bouncingBehavior: UIDynamicItemBehavior!
let infoLabel = UILabel()
// add segmented controls for collisionBoundsType and "Spread Layout"
let seg1 = UISegmentedControl(items: ["Ellipse", "Rectangle"])
let seg2 = UISegmentedControl(items: ["Overlaid", "Offset"])
override func viewDidLoad() {
super.viewDidLoad()
addSubViews()
[seg1, seg2, infoLabel].forEach { v in
v.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(v)
}
infoLabel.numberOfLines = 0
infoLabel.font = .monospacedSystemFont(ofSize: 14.0, weight: .light)
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
seg1.topAnchor.constraint(equalTo: g.topAnchor, constant: 4.0),
seg1.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 8.0),
seg2.topAnchor.constraint(equalTo: g.topAnchor, constant: 4.0),
seg2.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -8.0),
infoLabel.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0),
infoLabel.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
infoLabel.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
])
seg1.selectedSegmentIndex = 0
seg2.selectedSegmentIndex = 0
// add a tap recognizer to start the Animator Behaviors
let t = UITapGestureRecognizer(target: self, action: #selector(gotTap(_:)))
view.addGestureRecognizer(t)
// run a Timer... every 1/10th second we'll fill the infoLabel with
// collisionBoundsType and a list of center points
// for all subviews
Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { timer in
if self.animator != nil {
var s = ""
for i in 0..<self.arr.count {
let c = self.arr[i].center
let xs = String(format: "%0.2f", c.x)
let ys = String(format: "%0.2f", c.y)
s += "\n\(i) - x: \(String(xs.paddingToLeft(upTo: 7))) y: \(String(ys.paddingToLeft(upTo: 9)))"
}
s += "\nAnimator is running: " + (self.animator.isRunning ? "Yes" : "No")
self.infoLabel.text = s
}
}
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
positionViews()
}
func positionViews() -> Void {
var x: CGFloat = 0.0
var y: CGFloat = 0.0
arr.forEach { v in
v.center = CGPoint(x: view.center.x + x, y: view.safeAreaInsets.top + 100.0 + y)
// if seg2 == Overlaid, position all views exactly on top of each other
// else, Offset the x,y center of each one by 0.1 pts
// Offsetting them allows the animator to use
// "valid" collision adjustments on start
if seg2.selectedSegmentIndex == 1 {
x += 0.1
y += 0.1
}
// set collisionBoundsType
v.useEllipse = seg1.selectedSegmentIndex == 0
}
}
@objc func gotTap(_ g: UIGestureRecognizer) -> Void {
positionViews()
addAnimatorAndBehaviors()
}
func addAnimatorAndBehaviors() {
animator = UIDynamicAnimator(referenceView: self.view)
gravity = UIGravityBehavior(items: arr)
animator.addBehavior(gravity)
collider = UICollisionBehavior(items: arr)
collider.translatesReferenceBoundsIntoBoundary = true
animator.addBehavior(collider)
bouncingBehavior = UIDynamicItemBehavior(items: arr)
bouncingBehavior.elasticity = 0.05
animator.addBehavior(bouncingBehavior)
}
func addSubViews() {
let clrs: [UIColor] = [
.red, .green, UIColor(red: 1.0, green: 0.85, blue: 0.55, alpha: 1.0),
UIColor(red: 1.0, green: 0.5, blue: 1.0, alpha: 1.0), .orange,
.cyan, .yellow, .magenta,
.systemTeal, .systemGreen,
]
for (c, i) in zip(clrs, (0..<clrs.count)) {
let v = createContainerView(with: c, number: i)
view.addSubview(v)
arr.append(v)
}
}
func createContainerView(with color: UIColor, number: Int) -> CustomContainerView {
let containerView = CustomContainerView()
containerView.backgroundColor = UIColor.brown.withAlphaComponent(0.2)
let size = CGSize(width: 50, height: 50)
containerView.frame.size = size
view.addSubview(containerView)
let roundLabel = UILabel()
roundLabel.translatesAutoresizingMaskIntoConstraints = false
roundLabel.backgroundColor = color
roundLabel.text = "\(number)"
roundLabel.textAlignment = .center
containerView.addSubview(roundLabel)
roundLabel.topAnchor.constraint(equalTo: containerView.topAnchor, constant: 10).isActive = true
roundLabel.leadingAnchor.constraint(equalTo: containerView.leadingAnchor, constant: 10).isActive = true
roundLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor, constant: -10).isActive = true
roundLabel.bottomAnchor.constraint(equalTo: containerView.bottomAnchor, constant: -10).isActive = true
roundLabel.layer.masksToBounds = true
roundLabel.layoutIfNeeded()
roundLabel.layer.cornerRadius = roundLabel.frame.height / 2
roundLabel.layer.borderWidth = 1
roundLabel.layer.borderColor = UIColor.white.cgColor
// let's add a CAShapeLayer to show the ellipse bounds
let c = CAShapeLayer()
c.fillColor = UIColor.clear.cgColor
c.lineWidth = 1
c.strokeColor = UIColor.black.cgColor
c.path = UIBezierPath(ovalIn: CGRect(origin: .zero, size: size)).cgPath
containerView.layer.addSublayer(c)
return containerView
}
}
值得注意的是：当collisionBoundsType == .ellipse 和视图完全在彼此之上开始时，碰撞算法可以（并且通常确实）最终将几个视图推离底部，这将它们置于 参考之外系统的界限。此时，算法会继续尝试碰撞这些视图，将它们推到 Y 轴上越来越远的位置。
这是让它运行几秒钟后的输出：
视图 5、7 和 8 方式超出范围，动画师仍在运行。这些视图将继续被推得越来越低，大概直到我们得到一个无效点崩溃（我没有让它运行足够长的时间来发现）。
此外，由于动画师最终对这些越界视图进行了大量处理，因此对剩余视图的碰撞检测会受到影响。