如何在大于或等于约束的超级视图中居中两个视图
How to center two views in super view with greater than or equal to constraints
我用两个标签做了一个例子 ViewController 来突出我的问题。目标是将标签垂直分隔 10,然后使用大于或等于约束将它们垂直居中。我使用的是视觉格式,但如果我设置像 view.topAnchor.constraint(greaterThan...
这样的约束,这应该适用。我还有两个约束来水平布局标签
我的ViewController:
class myVC: UIViewController {
lazy var titleLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "Hello World"
l.font = .systemFont(ofSize: 50)
l.textColor = .black
return l
}()
lazy var descLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "description"
l.font = .systemFont(ofSize: 35)
l.textColor = .gray
return l
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .yellow
view.addSubview(titleLabel)
view.addSubview(descLabel)
titleLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
descLabel.leadingAnchor.constraint(equalTo: titleLabel.leadingAnchor).isActive = true
NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:|-(<=50)-[titleLabel]-(10)-[descLabel]-(<=50)-|", options: .init(), metrics: nil, views: ["titleLabel": titleLabel, "descLabel": descLabel]))
}
}
这导致 。根据我的理解,这应该将视图分开 10 pts,并将标签垂直居中,因为在格式 "V:|-(<=50)-[titleLabel]-(10)-[descLabel]-(<=50)-|"
中我说标题标签顶部和 superView 顶部之间的距离应该至少为 (greaterThanOrEqualTo) 50,并且 description Label 的底部和 superView 的底部之间的距离应该至少为 50。如果我想让两个标签垂直居中,我的顶部和底部约束应该是什么样的?
是的,我知道我可以设置垂直和水平中心,但这是我为无法使用这些问题制作的示例。我需要能够以大于(或小于)或等于约束的视图为中心。
使用 VFL 很难使元素居中。
也很难将两个元素居中,除非它们嵌入 UIView
或 UIStackView
。
这是一个选项,将标签嵌入 "container" UIView
:
class MyVC: UIViewController {
lazy var titleLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "Hello World"
l.font = .systemFont(ofSize: 50)
l.textColor = .black
// center the text in the label - change to .left if desired
l.textAlignment = .center
return l
}()
lazy var descLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "description"
l.font = .systemFont(ofSize: 35)
l.textColor = .gray
// center the text in the label - change to .left if desired
l.textAlignment = .center
return l
}()
lazy var containerView: UIView = {
let v = UIView()
v.translatesAutoresizingMaskIntoConstraints = false
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .yellow
// give the labels and containerView background colors to make it easy to see the layout
titleLabel.backgroundColor = .green
descLabel.backgroundColor = .cyan
containerView.backgroundColor = .blue
// add containerView to view
view.addSubview(containerView)
// add labels to containerView
containerView.addSubview(titleLabel)
containerView.addSubview(descLabel)
NSLayoutConstraint.activate([
// constrain titleLabel Top to containerView Top
titleLabel.topAnchor.constraint(equalTo: containerView.topAnchor),
// constrain titleLabel Leading and Trailing to containerView Leading and Trailing
titleLabel.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
titleLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
// constrain descLabel Leading and Trailing to containerView Leading and Trailing
descLabel.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
descLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
// constrain descLabel Bottom to containerView Bottom
descLabel.bottomAnchor.constraint(equalTo: containerView.bottomAnchor),
// constrain descLabel Top 10-pts from titleLabel Bottom
descLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 10.0),
// constrain containerView centered horizontally and vertically
containerView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
containerView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
])
}
}
结果:
这可以通过使用 stackview 轻松实现。在 stackview 中添加两个标签,并将其在 superview 中垂直居中,并带有所有其他约束(顶部、前导、底部、尾随)。
这是您的用例的视图控制器示例代码。
class ViewController: UIViewController {
lazy var titleLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "Hello \nWorld"
label.font = .systemFont(ofSize: 50)
label.backgroundColor = .orange
label.numberOfLines = 0
label.textColor = .black
return label
}()
lazy var descLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "a\n b\n c\n"
label.font = .systemFont(ofSize: 35)
label.backgroundColor = .green
label.numberOfLines = 0
label.textColor = .gray
return label
}()
lazy var contentView: UIStackView = {
let stackView = UIStackView()
stackView.axis = .vertical
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.spacing = 10
stackView.distribution = .fill
return stackView
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
contentView.addArrangedSubview(titleLabel)
contentView.addArrangedSubview(descLabel)
self.view.addSubview(contentView)
let constraints = [
contentView.topAnchor.constraint(greaterThanOrEqualTo: view.safeAreaLayoutGuide.topAnchor),
contentView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
contentView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
contentView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
contentView.bottomAnchor.constraint(lessThanOrEqualTo: view.safeAreaLayoutGuide.bottomAnchor)
]
NSLayoutConstraint.activate(constraints)
}
}
上面的代码将产生这个视图,它继续占据顶部和底部 space 直到它遇到安全区域。此外,您可以设置垂直内容拥抱和压缩阻力优先级来控制扩展或收缩哪个标签。
我用两个标签做了一个例子 ViewController 来突出我的问题。目标是将标签垂直分隔 10,然后使用大于或等于约束将它们垂直居中。我使用的是视觉格式,但如果我设置像 view.topAnchor.constraint(greaterThan...
这样的约束,这应该适用。我还有两个约束来水平布局标签
我的ViewController:
class myVC: UIViewController {
lazy var titleLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "Hello World"
l.font = .systemFont(ofSize: 50)
l.textColor = .black
return l
}()
lazy var descLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "description"
l.font = .systemFont(ofSize: 35)
l.textColor = .gray
return l
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .yellow
view.addSubview(titleLabel)
view.addSubview(descLabel)
titleLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
descLabel.leadingAnchor.constraint(equalTo: titleLabel.leadingAnchor).isActive = true
NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:|-(<=50)-[titleLabel]-(10)-[descLabel]-(<=50)-|", options: .init(), metrics: nil, views: ["titleLabel": titleLabel, "descLabel": descLabel]))
}
}
这导致 "V:|-(<=50)-[titleLabel]-(10)-[descLabel]-(<=50)-|"
中我说标题标签顶部和 superView 顶部之间的距离应该至少为 (greaterThanOrEqualTo) 50,并且 description Label 的底部和 superView 的底部之间的距离应该至少为 50。如果我想让两个标签垂直居中,我的顶部和底部约束应该是什么样的?
是的,我知道我可以设置垂直和水平中心,但这是我为无法使用这些问题制作的示例。我需要能够以大于(或小于)或等于约束的视图为中心。
使用 VFL 很难使元素居中。
也很难将两个元素居中,除非它们嵌入 UIView
或 UIStackView
。
这是一个选项,将标签嵌入 "container" UIView
:
class MyVC: UIViewController {
lazy var titleLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "Hello World"
l.font = .systemFont(ofSize: 50)
l.textColor = .black
// center the text in the label - change to .left if desired
l.textAlignment = .center
return l
}()
lazy var descLabel: UILabel = {
let l = UILabel(frame: .zero)
l.translatesAutoresizingMaskIntoConstraints = false
l.text = "description"
l.font = .systemFont(ofSize: 35)
l.textColor = .gray
// center the text in the label - change to .left if desired
l.textAlignment = .center
return l
}()
lazy var containerView: UIView = {
let v = UIView()
v.translatesAutoresizingMaskIntoConstraints = false
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .yellow
// give the labels and containerView background colors to make it easy to see the layout
titleLabel.backgroundColor = .green
descLabel.backgroundColor = .cyan
containerView.backgroundColor = .blue
// add containerView to view
view.addSubview(containerView)
// add labels to containerView
containerView.addSubview(titleLabel)
containerView.addSubview(descLabel)
NSLayoutConstraint.activate([
// constrain titleLabel Top to containerView Top
titleLabel.topAnchor.constraint(equalTo: containerView.topAnchor),
// constrain titleLabel Leading and Trailing to containerView Leading and Trailing
titleLabel.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
titleLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
// constrain descLabel Leading and Trailing to containerView Leading and Trailing
descLabel.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
descLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
// constrain descLabel Bottom to containerView Bottom
descLabel.bottomAnchor.constraint(equalTo: containerView.bottomAnchor),
// constrain descLabel Top 10-pts from titleLabel Bottom
descLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 10.0),
// constrain containerView centered horizontally and vertically
containerView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
containerView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
])
}
}
结果:
这可以通过使用 stackview 轻松实现。在 stackview 中添加两个标签,并将其在 superview 中垂直居中,并带有所有其他约束(顶部、前导、底部、尾随)。 这是您的用例的视图控制器示例代码。
class ViewController: UIViewController {
lazy var titleLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "Hello \nWorld"
label.font = .systemFont(ofSize: 50)
label.backgroundColor = .orange
label.numberOfLines = 0
label.textColor = .black
return label
}()
lazy var descLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "a\n b\n c\n"
label.font = .systemFont(ofSize: 35)
label.backgroundColor = .green
label.numberOfLines = 0
label.textColor = .gray
return label
}()
lazy var contentView: UIStackView = {
let stackView = UIStackView()
stackView.axis = .vertical
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.spacing = 10
stackView.distribution = .fill
return stackView
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
contentView.addArrangedSubview(titleLabel)
contentView.addArrangedSubview(descLabel)
self.view.addSubview(contentView)
let constraints = [
contentView.topAnchor.constraint(greaterThanOrEqualTo: view.safeAreaLayoutGuide.topAnchor),
contentView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
contentView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
contentView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
contentView.bottomAnchor.constraint(lessThanOrEqualTo: view.safeAreaLayoutGuide.bottomAnchor)
]
NSLayoutConstraint.activate(constraints)
}
}
上面的代码将产生这个视图,它继续占据顶部和底部 space 直到它遇到安全区域。此外,您可以设置垂直内容拥抱和压缩阻力优先级来控制扩展或收缩哪个标签。