UIView 动画立即完成，不考虑持续时间或延迟

Question

我在为我的视图的 layoutConstraints 之一设置动画时遇到了一些困难：

UIView.animate(withDuration: 1, delay: 0, options: UIViewAnimationOptions.curveEaseInOut, animations: {
                self.topLayoutConstraint?.constant = self.currentYPosition
                self.layoutIfNeeded()
                }, completion: nil)

无论我使用什么持续时间或延迟，动画都会立即完成（我的视图从以前的位置跳到新的位置）。

我检查了所有的值，它们都是正确的。我也检查过，动画和完成被调用了。

有什么想法吗？

编辑：

@objc private func viewDragged(_ recognizer: UIPanGestureRecognizer) {

        let location = recognizer.location(in: self.superview)

        switch recognizer.state {
        case .ended:

            if (recognizer.direction == .Down) {            // Collapsing the slide panel

                currentYPosition = parentViewHeight - minimumVisibleHeight - statusBarHeight - navBarHeight
            }
            else if (recognizer.direction == .Up) {       // Expanding the slide panel

                // Substracting `minimumVisibleHeight` so that the dragable part is hidden behind the navigation bar
                currentYPosition = -minimumVisibleHeight
            }

            self.topLayoutConstraint?.constant = self.currentYPosition
            UIView.animate(withDuration: 1, delay: 0, options: UIViewAnimationOptions.curveEaseInOut, animations: {
                self.layoutIfNeeded()
                }, completion: nil)
            break
        case .began:
            HomeSlidePanelContainerView.draggingPreviousPosition = location.y
        default:
            self.layoutIfNeeded()

            if (location.y < (parentViewHeight - minimumVisibleHeight - statusBarHeight - navBarHeight)
                || location.y > (statusBarHeight + navBarHeight)) {

                currentYPosition -= HomeSlidePanelContainerView.draggingPreviousPosition - location.y
                topLayoutConstraint?.constant = currentYPosition
                self.layoutIfNeeded()
            }
            HomeSlidePanelContainerView.draggingPreviousPosition = location.y
            break
        }

    }

Answer 1

在动画块之前设置约束：

self.topLayoutConstraint?.constant = self.currentYPosition

UIView.animate(withDuration: 1, delay: 0, options: UIViewAnimationOptions.curveEaseInOut, animations: {               
                self.layoutIfNeeded()
}, completion: nil)

Answer 2

我经常用Snapkit或者Masonry做autolayout，也许你可以试试it.It熟悉Apple的autolayout，太棒了！比如我今天用的子代码：

UIView.animate(withDuration: 1.0, animations: {
 minLabel.snp.updateConstraints { (make) in
            make.top.equalTo(view.snp.centerY)
                    }
})
self.view.layoutIfNeeded()

Answer 3

我已经设法找到解决方案。这可能会对其他人有所帮助，所以我正在回答我自己的问题。

我当时做的是这样的：

self.topLayoutConstraint?.constant = self.currentYPosition

UIView.animate(withDuration: 1, delay: 0, options: UIViewAnimationOptions.curveEaseInOut, animations: {               
                self.layoutIfNeeded()
}, completion: nil)

如您所见，我正在更改一个值 topLayoutConstraint，这是对 self 的约束，后者是 UIView.

然后我尝试通过在动画闭包中调用 self.layoutIfNeeded 来为该变化设置动画。

这里的问题是 layoutIfNeeded() 适用于子视图而不是视图本身。所以在我的例子中，我试图为 self 的子视图而不是 self 本身的布局设置动画。

已将 self.layoutIfNeeded() 更改为 self.superview?.layoutIfNeeded() 瞧！

UIView 动画立即完成，不考虑持续时间或延迟

UIView animation is done instantly without regards to the duration or delay

uiviewanimation

ios

swift