我有一个需求需要更改 UIView 图层的锚点,但是更改锚点后视图无法移动。我知道当视图由 frame(CGRect:...) 定义时是可能的。像这样:
let width = SCREEN_WIDTH - 40
let view2 = UIView(frame: CGRect(x: 20, y: 300, width: width, height: 200))
view2.backgroundColor = .blue
self.view.addSubview(view2)
let oldFrame2 = view2.frame
view2.layer.anchorPoint = CGPoint(x: 0, y: 0.5)
view2.frame = oldFrame2
这行得通。
但是我的视图是由Autolayout定义的,我尝试了上面代码的解决方案,但它不起作用。代码:
let view1 = UIView()
view1.backgroundColor = .orange
self.view.addSubview(view1)
view1.snp.makeConstraints { (maker) in
maker.top.equalToSuperview().offset(50)
maker.leading.equalToSuperview().offset(20)
maker.trailing.equalToSuperview().offset(-20)
maker.height.equalTo(200)
}
let oldFrame1 = view1.frame
view1.layer.anchorPoint = CGPoint(x: 0, y: 0.5)
view1.frame = oldFrame1
结果是:橙色的view1被移动了,改变anchorPoint后应该和蓝色的view2一样。
那么有人可以给我一些建议吗?
------------------------------更新答案------------------ ------------
正如@DonMag 回答的那样,我们可以通过在使用自动布局时更新视图而不是框架的约束来实现这一要求。这是 SnapKit 的代码:
let view1 = UIView()
view1.backgroundColor = .orange
view1.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(view1)
view1.snp.makeConstraints { (maker) in
maker.top.equalToSuperview().offset(100)
maker.leading.equalToSuperview().offset(20)
maker.trailing.equalToSuperview().offset(-20)
maker.height.equalTo(200)
}
// important!!!
view1.layoutIfNeeded()
let oldFrame1 = view1.frame
view1.layer.anchorPoint = CGPoint(x: 0, y: 0.5)
// update constraints by updateConstraints function
// if you use @IBOutlet NSLayoutConstraint from xib,
// you can also just set xxx.constant = yyy to update the constraints.
view1.snp.updateConstraints { (maker) in
let subOffset = oldFrame1.width * 0.5
maker.leading.equalToSuperview().offset(20 - subOffset)
maker.trailing.equalToSuperview().offset(-20 - subOffset)
}
let width = SCREEN_WIDTH - 40
let view2 = UIView(frame: CGRect(x: 20, y: 300, width: width, height: 200))
view2.backgroundColor = .blue
self.view.addSubview(view2)
let oldFrame2 = view2.frame
view2.layer.anchorPoint = CGPoint(x: 0, y: 0.5)
view2.frame = oldFrame2
另一种解决方案是通过设置将自动布局视图更改为框架translatesAutoresizingMaskIntoConstraints = true
,如下所示:
let width = SCREEN_WIDTH - 40
let view1 = UIView()
view1.backgroundColor = .orange
self.view.addSubview(view1)
// Autolayout
view1.snp.makeConstraints { (maker) in
maker.top.equalToSuperview().offset(100)
maker.leading.equalToSuperview().offset(20)
maker.trailing.equalToSuperview().offset(-20)
maker.height.equalTo(200)
}
// change autolayout to frame
view1.translatesAutoresizingMaskIntoConstraints = true
view1.frame = CGRect(x: 20, y: 100, width: width, height: 200)
let oldFrame1 = view1.frame
view1.layer.anchorPoint = CGPoint(x: 0, y: 0.5)
view1.frame = oldFrame1
let view2 = UIView(frame: CGRect(x: 20, y: 300, width: width, height: 200))
view2.backgroundColor = .blue
self.view.addSubview(view2)
let oldFrame2 = view2.frame
view2.layer.anchorPoint = CGPoint(x: 0, y: 0.5)
view2.frame = oldFrame2