demo.gif
如图,这个动画的是如何做的呢?
分析:
- 1.环形进度指示器,根据下载进度来更新它
- 2.扩展环,向内向外扩展这个环,中间扩展的时候,去掉这个遮盖
一.环形进度指示器
1.自定义View继承UIView,命名为CircularLoaderView.swift,此View将用来保存动画的代码
2.创建CAShapeLayer
let circlePathLayer = CAShapeLayer()
let circleRadius: CGFloat = 20.0
3.初始化CAShapeLayer
// 两个初始化方法都调用configure方法
override init(frame: CGRect) {
super.init(frame: frame)
configure()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder : aDecoder)
configure()
}
// 初始化代码来配置这个shape layer:
func configure(){
circlePathLayer.frame = bounds
circlePathLayer.lineWidth = 2.0
circlePathLayer.fillColor = UIColor.clear.cgColor
circlePathLayer.strokeColor = UIColor.red.cgColor
layer.addSublayer(circlePathLayer)
backgroundColor = .white
progress = 0.0
}
4.设置环形进度条的矩形frame
// 小矩形的frame
func circleFrame() -> CGRect {
var circleFrame = CGRect(x: 0, y: 0, width: 2*circleRadius, height: 2*circleRadius)
let circlePathBounds = circlePathLayer.bounds
circleFrame.origin.x = circlePathBounds.midX - circleFrame.midX
circleFrame.origin.y = circlePathBounds.midY - circleFrame.midY
return circleFrame
}
可以参考下图,理解这个circleFrame
Snip20160705_3.png
5.每次自定义的这个view的size改变时，你都需要重新计算circleFrame，所以要将它放在一个独立的方法,方便调用
// 通过一个矩形（正方形）绘制椭圆（圆形）路径
func circlePath() -> UIBezierPath {
return UIBezierPath.init(ovalIn: circleFrame())
}
6.由于layers没有autoresizingMask这个属性，你需要在layoutSubviews方法中更新circlePathLayer的rame来恰当地响应view的size变化
override func layoutSubviews() {
super.layoutSubviews()
circlePathLayer.frame = bounds
circlePathLayer.path = circlePath().cgPath
}
7.给CircularLoaderView.swift文件添加一个CGFloat类型属性,自定义的setter和getter方法,setter方法验证输入值要在0到1之间，然后赋值给layer的strokeEnd属性。
var progress : CGFloat{
get{
return circlePathLayer.strokeEnd
}
set{
if (newValue > 1) {
circlePathLayer.strokeEnd = 1
}else if(newValue < 0){
circlePathLayer.strokeEnd = 0
}else{
circlePathLayer.strokeEnd = newValue
}
}
}
8.利用Kingfisher,在image下载回调方法中更新progress.
此处是自定义ImageView,在storyboard中拖个ImageView,设置为自定义的ImageView类型,在这个ImageView初始化的时候就会调用下面的代码
class CustomImageView: UIImageView {
// 创建一个实例对象
let progressIndicatorView = CircularLoaderView(frame: CGRect.zero)
// 从xib中加载会走这个方法
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
addSubview(progressIndicatorView)
progressIndicatorView.frame = bounds
let url = URL.init(string: "https://koenig-media.raywenderlich.com/uploads/2015/02/mac-glasses.jpeg")
self.kf.setImage(with: url, placeholder: nil, options: nil, progressBlock: { [weak self] (reseivdSize, expectedSize) in
self?.progressIndicatorView.progress = CGFloat(reseivdSize) / CGFloat(expectedSize)
}) { [weak self] (image, error, _, _) in
self?.progressIndicatorView.reveal()
}
}
}
二.扩展这个环
仔细看,此处是两个动画一起执行,1是向外扩展2.是向内扩展.但可以用一个Bezier path完成此动画,需要用到组动画.
- 1.增加圆的半径(path属性)来向外扩展
- 2.同时增加line的宽度(lineWidth属性)来使环更加厚和向内扩展
func reveal() {
// 背景透明，那么藏着后面的imageView将显示出来
backgroundColor = .clear
progress = 1.0
// 移除隐式动画,否则干扰reveal animation
circlePathLayer.removeAnimation(forKey: "strokenEnd")
// 从它的superLayer 移除circlePathLayer ,然后赋值给super的layer mask
circlePathLayer.removeFromSuperlayer()
// 通过这个这个circlePathLayer 的mask hole动画 ,image 逐渐可见
superview?.layer.mask = circlePathLayer
// 1 求出最终形状
let center = CGPoint(x:bounds.midX,y: bounds.midY)
let finalRadius = sqrt((center.x*center.x) + (center.y*center.y))
let radiusInset = finalRadius - circleRadius
let outerRect = circleFrame().insetBy(dx: -radiusInset, dy: -radiusInset)
// CAShapeLayer mask最终形状
let toPath = UIBezierPath.init(ovalIn: outerRect).cgPath
// 2 初始值
let fromPath = circlePathLayer.path
let fromLineWidth = circlePathLayer.lineWidth
// 3 最终值
CATransaction.begin()
// 防止动画完成跳回原始值
CATransaction.setValue(kCFBooleanTrue, forKey: kCATransactionDisableActions)
circlePathLayer.lineWidth = 2 * finalRadius
circlePathLayer.path = toPath
CATransaction.commit()
// 4 路径动画,lineWidth动画
let lineWidthAnimation = CABasicAnimation(keyPath: "lineWidth")
lineWidthAnimation.fromValue = fromLineWidth
lineWidthAnimation.toValue = 2*finalRadius
let pathAnimation = CABasicAnimation(keyPath: "path")
pathAnimation.fromValue = fromPath
pathAnimation.toValue = toPath
// 5 组动画
let groupAnimation = CAAnimationGroup()
groupAnimation.duration = 1
groupAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
groupAnimation.animations = [pathAnimation ,lineWidthAnimation]
groupAnimation.delegate = self
circlePathLayer.add(groupAnimation, forKey: "strokeWidth")
}
photo-loading-diagram.png
三.监听动画的结束
extension CircularLoaderView :CAAnimationDelegate {
// 移除mask
func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
superview?.layer.mask = nil
}
}
示例下载地址github
原文地址 Rounak Jain
参考地址
