我有一个动态宽度UILabel
(用于可见性的彩色灰绿色),它对邻居(绿色和红色视图)有一个固定的前导和尾随约束。我希望这个表在移动其中一个邻居时调整其宽度(圆角红色/绿色视图)。但是,我对这个更改的动画有一个问题,因为我的标签的宽度“跳转”到没有动画的新值。对于我的右对齐标签,这意味着文本本身也会跳转。
我正在制作红色/绿色视图的动作,如下所示:
- (void)show {
self.edgeConstraint.constant = 0;
[UIView animateWithDuration:0.25 animations:^{
[self.contentView layoutIfNeeded];
}];
}
- (void)hide {
self.edgeConstraint.constant = -100;
[UIView animateWithDuration:0.25 animations:^{
[self.contentView layoutIfNeeded];
}];
}
答案 0 :(得分:2)
问题在于UILabel
内容模式。您看到了类似的问题here。由于缩短了绘制文本的标签,因此标签会执行绘图传递,但它会使用动画块的最后一帧进行更新。创建平滑动画的最简单方法是使用greaterThanOrEqualTo
前导约束并将textAlignment
设置为.natural
。
当我这样做时,我得到的结果就是在底部设置textAlignment
.right
。
演示的源代码:
import UIKit
import PlaygroundSupport
final class ViewController: UIViewController {
var constraint: NSLayoutConstraint?
var otherConstraint: NSLayoutConstraint?
lazy private var sideView: UIView = {
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(view)
view.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
self.constraint = view.leadingAnchor.constraint(equalTo: self.view.trailingAnchor)
self.constraint?.isActive = true
view.widthAnchor.constraint(equalToConstant: 100).isActive = true
view.heightAnchor.constraint(equalToConstant: 44).isActive = true
view.backgroundColor = .yellow
return view
}()
lazy private var secondSideView: UIView = {
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(view)
view.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 44.0).isActive = true
self.otherConstraint = view.leadingAnchor.constraint(equalTo: self.view.trailingAnchor)
self.otherConstraint?.isActive = true
view.widthAnchor.constraint(equalToConstant: 100).isActive = true
view.heightAnchor.constraint(equalToConstant: 44).isActive = true
view.backgroundColor = .yellow
return view
}()
lazy private var label: UILabel = {
let label = UILabel()
label.text = "Label"
label.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(label)
label.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
label.leadingAnchor.constraint(greaterThanOrEqualTo: self.view.leadingAnchor, constant: 8.0).isActive = true
label.trailingAnchor.constraint(equalTo: self.sideView.leadingAnchor).isActive = true
return label
}()
lazy private var secondLabel: UILabel = {
let label = UILabel()
label.textAlignment = .right
label.text = "Label"
label.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(label)
label.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 44.0).isActive = true
label.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 8.0).isActive = true
label.trailingAnchor.constraint(equalTo: self.sideView.leadingAnchor).isActive = true
return label
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
self.secondSideView.isHidden = false
self.secondLabel.isHidden = false
self.sideView.isHidden = false
self.label.isHidden = false
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
self.perform(#selector(self.showSideView), with: nil, afterDelay: 5.0)
}
@objc private func showSideView() {
self.view.layoutIfNeeded()
UIView.animate(withDuration: 1.5, delay: 0.0, options: [.autoreverse, .repeat], animations: {
self.otherConstraint?.constant = -100
self.constraint?.constant = -100
self.view.layoutIfNeeded()
})
}
}
PlaygroundPage.current.liveView = ViewController()