iOS 动画进阶 - 实现炫酷的上拉刷新动效

AnnKelleher 2年前
   <p>最近撸了一个上拉刷新的小轮子,只要遵循一个协议就能自定义自己动效的上拉刷新和加载,我自己也写了几个动效进去,下面是一个比较好的动效的实现过程</p>    <p>先上效果图和 <a href="/misc/goto?guid=4959742176572986662" rel="nofollow,noindex">github地址</a> ,有其他好的动效大家也可以交流~</p>    <p><img src="https://simg.open-open.com/show/844ccae44251427561ddfc78025fe076.gif"></p>    <p>动效的 <a href="/misc/goto?guid=4959742176670606055" rel="nofollow,noindex">原地址</a> ,在uimovement网站上看到这个动效时感觉特别6,就想自己实现一下,费了很长时间,换了几种方案终于实现出来了,下面是实现的步骤:</p>    <h2>分析动效</h2>    <p>写一个动效的第一步就应该仔细的去分析它,把它的每一帧展开来看,找一个最合适的方式来实现它,下面是我分析过程:</p>    <ul>     <li>看到曲线,肯定会想到 CAShapeLayer 和 UIBezierPath 这一对搭档,相对于 CoreGraphics 而言,它即简单有高效;</li>     <li>曲线的拉拽效果可以用 CADisplayLink 加上一个参考的 view ,以参考 view 为 UIBezierPath 的一个 controlPoint ,移动参考 view 来实现曲线拉拽的效果;</li>     <li>曲线的回弹效果考虑再三后决定使用 CAKeyframeAnimation 配合 CAShapeLayer 来使用,本来打算使用 CASpringanimation 来实现,但是考虑它是 iOS9 出的,而我的轮子最低支持iOS8,就放弃用它了;</li>     <li>小球是实现和弹出就相对简单了,使用 CAShapeLayer 来实现小球,用 CABasicAnimation 来实现小球的移动;</li>     <li>小球外层圆环旋转的效果,首先也是用 CAShapeLayer 来实现圆环,然后配合 CABasicAnimation 控制 CAShapeLayer 的 strokeEnd 和 transform.rotation.z 一直来实现外层圆环旋转的效果;</li>     <li>最后就是比较复杂的就是小球和曲线的连接处的处理,我的实现方式是通过 CADisplayLink 在动画的过程中实时的去监听小球和曲线的位置,计算出 UIBezierPath 用一个 CAShapeLayer 来精确的连接小球和曲线部分。</li>    </ul>    <p>好了,以上是大概过程,如果大家有另外的更好的实现方式,也可以一起来讨论。</p>    <h2>绘制曲线和曲线的拉拽</h2>    <p>我们用 CAShapeLayer 和 UIBezierPath 这一对搭档来实现曲线的绘制,下面以一个参考 view 来给大家演示一下,下面是主要代码和效果图:</p>    <p><img src="https://simg.open-open.com/show/7aa990e2f5164be62e337c04629ffbdd.gif"></p>    <pre>  <code class="language-objectivec">// 通过传递的y坐标来绘制曲线  func wave(_ y: CGFloat, execute: CGFloat) {      self.execute = execute      waveLayer.path = wavePath(x: 0, y: y)      if !isAnimation {          var trans = CGAffineTransform.identity          trans = trans.translatedBy(x: 0, y: y)          reference.transform = trans      }  }    // 计算path  private func wavePath(x: CGFloat, y: CGFloat) -> CGPath {      let w = frame.width      let path = UIBezierPath()      if y < execute {          path.move(to: .zero)          path.addLine(to: .init(x: w, y: 0))          path.addLine(to: .init(x: w, y: y))          path.addLine(to: .init(x: 0, y: y))          path.addLine(to: .zero)      }else {          path.move(to: .zero)          path.addLine(to: .init(x: w, y: 0))          path.addLine(to: .init(x: w, y: execute))          path.addQuadCurve(to: .init(x: 0, y: execute), controlPoint: .init(x: w/2, y: y))          path.addLine(to: .zero)      }      return path.cgPath  }</code></pre>    <h2>曲线的回弹效果</h2>    <p>曲线的回弹使用 CAKeyframeAnimation 加到参考的 view 上,然后用 CADisplayLink 监听参考 view 的坐标做为 controlPoint 来实现曲线的回弹效果,下面是主要代码和效果图:</p>    <p><img src="https://simg.open-open.com/show/0ea27041b6a5d1821c4e066a293001ce.gif"></p>    <pre>  <code class="language-objectivec">// 开始动画  func startAnimation() {      isAnimation = true      addDisPlay()      boundAnimation(x: 0, y: execute)  }    // CAKeyframeAnimation动画  private func boundAnimation(x: CGFloat, y: CGFloat) {      let bounce = CAKeyframeAnimation(keyPath: "transform.translation.y")      bounce.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)      bounce.duration = bounceDuration      bounce.values = [          reference.frame.origin.y,          y * 0.5,          y * 1.2,          y * 0.8,          y * 1.1,          y      ]      bounce.isRemovedOnCompletion = true      bounce.fillMode = kCAFillModeForwards      bounce.delegate = self      reference.layer.add(bounce, forKey: "return")  }    // 添加和移除CADisplayLink  private func addDisPlay() {      displayLink = CADisplayLink(target: self, selector: #selector(displayAction))      displayLink?.add(to: .main, forMode: .commonModes)  }    private func removeDisPlay() {      displayLink?.invalidate()      displayLink = nil  }    // CADisplayLink绑定的方法  @objc private func displayAction() {      if let frame = reference.layer.presentation()?.frame {          DispatchQueue.global().async {              let path = self.displayWavePath(x: 0, y: frame.origin.y + referenceHeight/2)              DispatchQueue.main.async {                  self.waveLayer.path = path              }          }      }  }    // 通过这个方法获取path  private func displayWavePath(x: CGFloat, y: CGFloat) -> CGPath {      let w = frame.width      let path = UIBezierPath()      path.move(to: .zero)      path.addLine(to: .init(x: w, y: 0))      path.addLine(to: .init(x: w, y: execute))      path.addQuadCurve(to: .init(x: 0, y: execute), controlPoint: .init(x: w/2, y: y))      path.addLine(to: .zero)      return path.cgPath  }</code></pre>    <h2>外层圆环的动画</h2>    <p>小球和外层圆环我们用 CAShapeLayer 来绘制,这里主要讲的是动画的实现,动画主要由两个部分组成:</p>    <ul>     <li>CABasicAnimation 控制外层圆环的 strokeEnd 的动画;</li>     <li>CABasicAnimation 控制外层圆环的 transform.rotation.z 的旋转动画;</li>    </ul>    <table>     <thead>      <tr>       <th>外层圆环的 strokeEnd 动画</th>       <th>外层圆环的 transform.rotation.z 的旋转动画</th>      </tr>     </thead>     <tbody>      <tr>       <td><img src="https://simg.open-open.com/show/0ae6365204df52b75129a0b862cb9ad0.gif"></td>       <td><img src="https://simg.open-open.com/show/b5e5a96bcb53c111a6c6f0c25214a273.gif"></td>      </tr>     </tbody>    </table>    <p>下面是关键代码:</p>    <pre>  <code class="language-objectivec">func animation() {      self.isHidden = false      let rotate = CABasicAnimation(keyPath: "transform.rotation.z")      rotate.fromValue = 0      rotate.toValue = M_PI * 2      rotate.duration = 1      rotate.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)      rotate.repeatCount = HUGE      rotate.fillMode = kCAFillModeForwards      rotate.isRemovedOnCompletion = false      self.add(rotate, forKey: rotate.keyPath)      strokeEndAnimation()  }    func strokeEndAnimation() {      let endPoint = CABasicAnimation(keyPath: "strokeEnd")      endPoint.fromValue = 0      endPoint.toValue = 1      endPoint.duration = 1.8      endPoint.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)      endPoint.repeatCount = HUGE      endPoint.fillMode = kCAFillModeForwards      endPoint.isRemovedOnCompletion = false      endPoint.delegate = self      add(endPoint, forKey: endPoint.keyPath)  }</code></pre>    <h2>小球上升和连接处的处理</h2>    <p>小球上升动画很简单,一个 CABasicAnimation 动画就实现了,主要麻烦的是连接处的动画实现,我的方案是在小球动画过程中通过 CADisplayLink 实时监听小球和参考 view 的位置,计算出贝斯尔曲线,然后通过一个名为 linkLayer: CAShapeLayer 的 layer 来连接它们,然后让它们在特定的地方断开,下面是主要代码和效果图:</p>    <p><img src="https://simg.open-open.com/show/a89b47b8ac64f37381812b064ad4981f.gif"></p>    <pre>  <code class="language-objectivec">@objc private func displayAction() {      let offY = ballLayer.circleLayer.presentation()?.frame.origin.y      let frame1 = ballLayer.frame      let frame2 = wavelayer.reference.layer.presentation()?.frame          if let offY = offY, let frame2 = frame2 {              DispatchQueue.global().async {                  // 判断是球是向上还是下,false为上,速度快时,获取的位置不及时,向下时需要调整位置                  let isIncrement = (offY - self.previousOffY) > 0                  let path = UIBezierPath()                  let x1 = frame1.origin.x + (isIncrement ? 4 : 0)                  let y1 = frame1.origin.y + offY                  let w1 = frame1.size.width - (isIncrement ? 8 : 0)                  let h1 = frame1.size.height                  let x2 = frame2.origin.x                  let y2 = frame2.origin.y                  let w2 = frame2.size.width                  let h2 = frame2.size.height                  let subY = y2 - y1                  // y1和y2的间距                  let subScale = subY/self.execute/2                  // 断开的距离为10                  let executeSub = self.ballLayer.circleLayer.moveUpDist + offY                  if executeSub < 10 {                      if !isIncrement {                          let executeSubScale = executeSub/10                          path.move(to: .init(x: x1 - 15, y: y2 + h2/2 + 15))                          path.addLine(to: .init(x: x1 + w1 + 15, y: y2 + h2/2 + 15))                          path.addQuadCurve(to: .init(x: x1 - 15, y: y2 + h2/2 + 15), controlPoint: .init(x: x1 + w1/2, y: y2 + h2/2 - self.execute/6 * executeSubScale))                      }                  }else {                      path.move(to: .init(x: x2 , y: y2 + h2))                      path.addLine(to: .init(x: x2 + w2, y: y2 + h2))                      path.addQuadCurve(to: .init(x: x1 + w1, y: y1 + h1/2), controlPoint: .init(x: x1 + w1 - w1*2*subScale, y: y1 + (y2 - y1)/2 + h1/2 + h2/2))                      path.addLine(to: .init(x: x1, y: y1 + h1/2))                      path.addQuadCurve(to: .init(x: x2 , y: y2 + h2), controlPoint: .init(x: x1 + w1*2*subScale, y: y1 + (y2 - y1)/2 + h1/2 + h2/2))                      if y1 + h1 <= self.execute, isIncrement {                          DispatchQueue.main.async {                              self.wavelayer.startDownAnimation()                          }                      }                  }                  DispatchQueue.main.async {                      self.linkLayer.path = path.cgPath                  }                  self.previousOffY = offY              }          }  }</code></pre>    <p>我觉得我这个地方的处理不是很好,但是简单粗暴的解决了问题,如果大家有更好的建议,可以提出来,大家一起交流学习~</p>    <p>完整的代码,大家可以去 <a href="/misc/goto?guid=4959742176572986662" rel="nofollow,noindex">github地址</a> 去下载,欢迎大家star和发表意见和贡献代码,有好的动效的话也可以提供,最后谢谢大家的阅读</p>    <p> </p>    <p>来自:http://blog.csdn.net/wang631106979/article/details/62888435</p>    <p> </p>