在Swift自定义动画中正确处理/清理CADisplayLink等?
请考虑使用在Swift自定义动画中正确处理/清理CADisplayLink等?,swift,animation,cadisplaylink,Swift,Animation,Cadisplaylink,请考虑使用CADisplayLink,执行这个简单的同步动画 var link:CADisplayLink? var startTime:Double = 0.0 let animTime:Double = 0.2 let animMaxVal:CGFloat = 0.4 private func yourAnim() { if ( link != nil ) { link!.paused = true //A:
CADisplayLink
,执行这个简单的同步动画
var link:CADisplayLink?
var startTime:Double = 0.0
let animTime:Double = 0.2
let animMaxVal:CGFloat = 0.4
private func yourAnim()
{
if ( link != nil )
{
link!.paused = true
//A:
link!.removeFromRunLoop(
NSRunLoop.mainRunLoop(), forMode:NSDefaultRunLoopMode)
link = nil
}
link = CADisplayLink(target: self, selector: #selector(doorStep) )
startTime = CACurrentMediaTime()
link!.addToRunLoop(
NSRunLoop.currentRunLoop(), forMode:NSDefaultRunLoopMode)
}
func doorStep()
{
let elapsed = CACurrentMediaTime() - startTime
var ping = elapsed
if (elapsed > (animTime / 2.0)) {ping = animTime - elapsed}
let frac = ping / (animTime / 2.0)
yourAnimFunction(CGFloat(frac) * animMaxVal)
if (elapsed > animTime)
{
//B:
link!.paused = true
link!.removeFromRunLoop(
NSRunLoop.mainRunLoop(), forMode:NSDefaultRunLoopMode)
link = nil
yourAnimFunction(0.0)
}
}
func killAnimation()
{
// for example if the cell disappears or is reused
//C:
????!!!!
}
似乎有各种各样的问题
在(A:),即使链接
不为空,也可能无法将其从运行循环中删除。(例如,可能有人用link=link:CADisplayLink()
对其进行了初始化-请尝试崩溃。)
第二,在(B:)看起来是一团糟。。。当然有更好(更快捷)的方法,如果时间刚过,它是零呢
最后在(C:)中,如果你想打破动画。。。我很沮丧,不知道什么是最好的
实际上,A:和B:的代码应该是相同的调用,这是一种清理调用。下面是一个简单的示例,演示如何实现
CADisplayLink
(在Swift 3中):
注意事项:
- 我们在这里使用
来表示显示链接未运行的状态,因为没有简单的方法可以从无效的显示链接获取此信息nil
- 我们使用的不是
,而是removeFromRunLoop()
,如果显示链接尚未添加到运行循环中,则不会崩溃。但是,这种情况一开始就不应该出现,因为我们总是在创建显示链接后立即将其添加到运行循环中invalidate()
- 我们将
设置为私有,以防止外部类将其置于意外状态(例如,使其无效,但不将其设置为displayLink
)nil
- 我们有一个
方法,它既可以使显示链接无效(如果它不是nil),也可以将其设置为stopDisplayLink()
——而不是复制和粘贴此逻辑nil
- 在使显示链接无效之前,我们不会将
设置为paused
,因为这是多余的true
- 检查非nil后,我们使用可选的链接,例如
(如果显示链接不是nil,将调用displayLink?.invalidate()
)。虽然强制展开在您给定的情况下可能是“安全的”(因为您正在检查是否为零)——但在未来重构时,它可能是不安全的,因为您可能会在不考虑这对强制展开有什么影响的情况下重新构造逻辑invalidate()
- 我们将
限制为动画持续时间,以确保后期动画逻辑不会产生超出预期范围的值已用时间
- 我们的更新方法
根据需要使用一个displayLinkDidFire(:)
类型的参数CADisplayLink
// defines an interface for receiving display update notifications
protocol DisplayUpdateReceiver: class {
func displayWillUpdate(deltaTime: CFTimeInterval)
}
接下来,我们将定义显示链接包装器类。此类将在初始化时接受委托引用。初始化后,它将自动启动我们的显示链接,并在Denit上进行清理
import UIKit
class DisplayUpdateNotifier {
// **********************************************
// MARK: Variables
// **********************************************
/// A weak reference to the delegate/listener that will be notified/called on display updates
weak var listener: DisplayUpdateReceiver?
/// The display link that will be initiating our updates
internal var displayLink: CADisplayLink? = nil
/// Tracks the timestamp from the previous displayLink call
internal var lastTime: CFTimeInterval = 0.0
// **********************************************
// MARK: Setup & Tear Down
// **********************************************
deinit {
stopDisplayLink()
}
init(listener: DisplayUpdateReceiver) {
// setup our delegate listener reference
self.listener = listener
// setup & kick off the display link
startDisplayLink()
}
// **********************************************
// MARK: CADisplay Link
// **********************************************
/// Creates a new display link if one is not already running
private func startDisplayLink() {
guard displayLink == nil else {
return
}
displayLink = CADisplayLink(target: self, selector: #selector(linkUpdate))
displayLink?.add(to: .main, forMode: .commonModes)
lastTime = 0.0
}
/// Invalidates and destroys the current display link. Resets timestamp var to zero
private func stopDisplayLink() {
displayLink?.invalidate()
displayLink = nil
lastTime = 0.0
}
/// Notifier function called by display link. Calculates the delta time and passes it in the delegate call.
@objc private func linkUpdate() {
// bail if our display link is no longer valid
guard let displayLink = displayLink else {
return
}
// get the current time
let currentTime = displayLink.timestamp
// calculate delta (
let delta: CFTimeInterval = currentTime - lastTime
// store as previous
lastTime = currentTime
// call delegate
listener?.displayWillUpdate(deltaTime: delta)
}
}
要使用它,只需初始化包装器的一个实例,传入委托侦听器引用,然后根据增量时间更新动画。在本例中,代理将更新调用传递给可设置动画的视图(这样,您可以跟踪多个设置动画的视图,并让每个视图通过此调用更新其位置)
我们的移动视图更新功能如下所示:
func update(deltaTime: CFTimeInterval) -> Bool {
guard canAnimate == true, isReadyForReuse == false else {
return false
}
// by multiplying our x/y values by the delta time new values are generated that will generate a smooth animation independent of the framerate.
let smoothVel = CGPoint(x: CGFloat(Double(velocity.x)*deltaTime), y: CGFloat(Double(velocity.y)*deltaTime))
let smoothAccel = CGPoint(x: CGFloat(Double(acceleration.x)*deltaTime), y: CGFloat(Double(acceleration.y)*deltaTime))
// update velocity with smoothed acceleration
velocity.adding(point: smoothAccel)
// update center with smoothed velocity
center.adding(point: smoothVel)
currentTime += 0.01
if currentTime >= timeLimit {
canAnimate = false
endAnimation()
return false
}
return true
}
如果您想浏览完整的演示项目,可以从GitHub下载:以上是如何高效使用CADisplayLink的最佳示例。多亏了@Fattie和@digitalHound 我忍不住在使用WKWebView的PdfViewer中添加了“digitalHound”对CADisplayLink和DisplayUpdater类的使用。 我的要求是继续以用户可选择的速度自动滚动pdf 这里的答案可能不正确,但我打算在这里展示CADisplayLink的用法。(对于像我这样的其他人,谁能实现他们的要求。) 此示例可能会被“修改”以加载网页并以用户选择的速度自动滚动 问候
桑杰。谢谢。。。“因为没有简单的方法可以从无效的显示链接获取此信息。”。。。嗯,这似乎是一个关键点。现在就完成你的答案,谢谢。PS:你觉得这些天展示Swift2之前的代码值得吗??也许把它扔掉会更好…:O@JoeBlowNSRunLoop注释不是Swift 2之前的代码,而是Swift 2代码–其余是Swift 3;)我只是在Xcode 8仍处于测试阶段时添加了它,所以很多人仍在使用Swift 2。关于检测显示链接何时失效,或者没有添加到运行循环中,苹果似乎更愿意从我们这里提取这些细节。尽管如此,在很少的情况下你真的需要这些信息。很多时候(例如在上面的示例中),您只有一个对显示链接的引用,一旦完成,就取消分配它。@JoeBlow尽管如此,根据具体的用例,您始终可以创建一个显示链接包装器
class ViewController: UIViewController, DisplayUpdateReceiver {
var displayLinker: DisplayUpdateNotifier?
var animView: MoveableView?
override func viewDidLoad() {
super.viewDidLoad()
// setup our animatable view and add as subview
animView = MoveableView.init(frame: CGRect.init(x: 150.0, y: 400.0, width: 20.0, height: 20.0))
animView?.configureMovement()
animView?.backgroundColor = .blue
view.addSubview(animView!)
// setup our display link notifier wrapper class
displayLinker = DisplayUpdateNotifier.init(listener: self)
}
// implement DisplayUpdateReceiver function to receive updates from display link wrapper class
func displayWillUpdate(deltaTime: CFTimeInterval) {
// pass the update call off to our animating view or views
_ = animView?.update(deltaTime: deltaTime)
// in this example, the animatable view will remove itself from its superview when its animation is complete and set a flag
// that it's ready to be used. We simply check if it's ready to be recycled, if so we reset its position and add it to
// our view again
if animView?.isReadyForReuse == true {
animView?.reset(center: CGPoint.init(x: CGFloat.random(low: 20.0, high: 300.0), y: CGFloat.random(low: 20.0, high: 700.0)))
view.addSubview(animView!)
}
}
}
func update(deltaTime: CFTimeInterval) -> Bool {
guard canAnimate == true, isReadyForReuse == false else {
return false
}
// by multiplying our x/y values by the delta time new values are generated that will generate a smooth animation independent of the framerate.
let smoothVel = CGPoint(x: CGFloat(Double(velocity.x)*deltaTime), y: CGFloat(Double(velocity.y)*deltaTime))
let smoothAccel = CGPoint(x: CGFloat(Double(acceleration.x)*deltaTime), y: CGFloat(Double(acceleration.y)*deltaTime))
// update velocity with smoothed acceleration
velocity.adding(point: smoothAccel)
// update center with smoothed velocity
center.adding(point: smoothVel)
currentTime += 0.01
if currentTime >= timeLimit {
canAnimate = false
endAnimation()
return false
}
return true
}
//
// PdfViewController.swift
//
import UIKit
import WebKit
class PdfViewController: UIViewController, DisplayUpdateReceiver {
@IBOutlet var mySpeedScrollSlider: UISlider! // UISlider in storyboard
var displayLinker: DisplayUpdateNotifier?
var myPdfFileName = ""
var myPdfFolderPath = ""
var myViewTitle = "Pdf View"
var myCanAnimate = false
var mySlowSkip = 0.0
// 0.125<=slow, 0.25=normal, 0.5=fast, 0.75>=faster
var cuScrollSpeed = 0.25
fileprivate var myPdfWKWebView = WKWebView(frame: CGRect.zero)
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
self.title = myViewTitle
let leftItem = UIBarButtonItem(title: "Back", style: .plain, target: self, action: #selector(PdfViewController.PdfBackClick))
navigationItem.leftBarButtonItem = leftItem
self.view.backgroundColor = UIColor.white.cgColor
mySpeedScrollSlider.minimumValue = 0.05
mySpeedScrollSlider.maximumValue = 4.0
mySpeedScrollSlider.isContinuous = true
mySpeedScrollSlider.addTarget(self, action: #selector(PdfViewController.updateSlider), for: [.valueChanged])
mySpeedScrollSlider.setValue(Float(cuScrollSpeed), animated: false)
mySpeedScrollSlider.backgroundColor = UIColor.white.cgColor
self.configureWebView()
let folderUrl = URL(fileURLWithPath: myPdfFolderPath)
let url = URL(fileURLWithPath: myPdfFolderPath + myPdfFileName)
myPdfWKWebView.loadFileURL(url, allowingReadAccessTo: folderUrl)
}
//MARK: - Button Action
@objc func PdfBackClick()
{
_ = self.navigationController?.popViewController(animated: true)
}
@objc func updateSlider()
{
if ( mySpeedScrollSlider.value <= mySpeedScrollSlider.minimumValue ) {
myCanAnimate = false
} else {
myCanAnimate = true
}
cuScrollSpeed = Double(mySpeedScrollSlider.value)
}
fileprivate func configureWebView() {
myPdfWKWebView.frame = view.bounds
myPdfWKWebView.translatesAutoresizingMaskIntoConstraints = false
myPdfWKWebView.navigationDelegate = self
myPdfWKWebView.isMultipleTouchEnabled = true
myPdfWKWebView.scrollView.alwaysBounceVertical = true
myPdfWKWebView.layer.backgroundColor = UIColor.red.cgColor //test
view.addSubview(myPdfWKWebView)
myPdfWKWebView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor ).isActive = true
myPdfWKWebView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
myPdfWKWebView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
myPdfWKWebView.bottomAnchor.constraint(equalTo: mySpeedScrollSlider.topAnchor).isActive = true
}
//MARK: - DisplayUpdateReceiver delegate
func displayWillUpdate(deltaTime: CFTimeInterval) {
guard myCanAnimate == true else {
return
}
var maxSpeed = 0.0
if cuScrollSpeed < 0.5 {
if mySlowSkip > 0.25 {
mySlowSkip = 0.0
} else {
mySlowSkip += cuScrollSpeed
return
}
maxSpeed = 0.5
} else {
maxSpeed = cuScrollSpeed
}
let scrollViewHeight = self.myPdfWKWebView.scrollView.frame.size.height
let scrollContentSizeHeight = self.myPdfWKWebView.scrollView.contentSize.height
let scrollOffset = self.myPdfWKWebView.scrollView.contentOffset.y
let xOffset = self.myPdfWKWebView.scrollView.contentOffset.x
if (scrollOffset + scrollViewHeight >= scrollContentSizeHeight)
{
return
}
let newYOffset = CGFloat( max( min( deltaTime , 1 ), maxSpeed ) )
self.myPdfWKWebView.scrollView.setContentOffset(CGPoint(x: xOffset, y: scrollOffset+newYOffset), animated: false)
}
}
extension PdfViewController: WKNavigationDelegate {
// MARK: - WKNavigationDelegate
public func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
//print("didStartProvisionalNavigation")
}
public func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
//print("didFinish")
displayLinker = DisplayUpdateNotifier.init(listener: self)
myCanAnimate = true
}
public func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
//print("didFailProvisionalNavigation error:\(error)")
}
public func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
//print("didFail")
}
}
func callPdfViewController( theFileName:String, theFileParentPath:String){
if ( !theFileName.isEmpty && !theFileParentPath.isEmpty ) {
let pdfViewController = self.storyboard!.instantiateViewController(withIdentifier: "PdfViewController") as? PdfViewController
pdfViewController?.myPdfFileName = theFileName
pdfViewController?.myPdfFolderPath = theFileParentPath
self.navigationController!.pushViewController(pdfViewController!, animated: true)
} else {
// Show error.
}
}