UIView.animateWithDuration 不应用转换

Question

我正在尝试在两个视图之间创建旋转过渡效果。为此，我使用比例变换。

我的问题是第一个动画由于某种原因没有动画：视图就消失了。第二个动画按预期执行。有任何想法吗？谢谢

  private func replace(
    _ source: UIView,
    with destination: UIView,
    usingRotationEffect: Void
  ) {
    let collapsed = CGAffineTransform(scaleX: 0, y: 1)
    let expanded = CGAffineTransform.identity

    source.isHidden = false
    source.transform = expanded

    destination.isHidden = true
    destination.transform = collapsed

    UIView.animate(
      withDuration: 1,
      delay: 0,
      options: .curveLinear,
      animations: {
        source.transform = collapsed
      },
      completion: { _ in
        source.isHidden = true
        destination.isHidden = false

        UIView.animate(
          withDuration: 1,
          delay: 0,
          options: .curveLinear,
          animations: {
            destination.transform = expanded
          })
      })
  }

Answer 1

这是一个已知问题，即 CGAffineTransform 中的零比例未正确设置动画。这是因为它使用矩阵计算每一帧的变换，并且比例因子为零，因此无法执行这些计算

因此，解决方法是使用 非常小但非零的 值，例如：

private func replace(
        _ source: UIView,
        with destination: UIView,
        usingRotationEffect: Void
      ) {
        let collapsed = CGAffineTransform(scaleX: 0.0001, y: 1)
        let expanded = CGAffineTransform.identity

        source.isHidden = false
        source.transform = expanded

        destination.isHidden = true
        destination.transform = collapsed

        UIView.animate(
          withDuration: 1,
          delay: 0,
          options: .curveLinear,
          animations: {
            source.transform = collapsed
          },
          completion: { _ in
            source.isHidden = true
            destination.isHidden = false

            UIView.animate(
              withDuration: 1,
              delay: 0,
              options: .curveLinear,
              animations: {
                destination.transform = expanded
              })
          })
      }

UIView.animateWithDuration 不应用转换

UIView.animateWithDuration doesn't apply transform

animation

uikit

swift