Swift以编程方式添加的约束不起作用
我在滚动视图中有一个视图: 现在我想以编程方式将子视图添加到该视图中。这就是我的代码:Swift以编程方式添加的约束不起作用,swift,uikit,constraints,programmatically-created,Swift,Uikit,Constraints,Programmatically Created,我在滚动视图中有一个视图: 现在我想以编程方式将子视图添加到该视图中。这就是我的代码: 子视图(工作) 现在我重复执行此代码: private func makeTextLabel(text: NSAttributedString, bgColor: UIColor?, maxWidth: CGFloat?) -> UILabel { //Creates label let label = UILabel() label.translatesAutoresizi
private func makeTextLabel(text: NSAttributedString, bgColor: UIColor?, maxWidth: CGFloat?) -> UILabel {
//Creates label
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
lv.addSubview(label)
//Adjustments
if(bgColor != nil) {
label.backgroundColor = bgColor
}
label.textColor = UIColor.black
label.attributedText = text
label.numberOfLines = 0
label.lineBreakMode = NSLineBreakMode.byWordWrapping
let width = maxWidth ?? lv.frame.size.width-8
label.widthAnchor.constraint(equalToConstant: width).isActive = true
label.heightAnchor.constraint(equalToConstant: heightForLabel(attributedText: label.attributedText, width: width)).isActive = true
label.leadingAnchor.constraint(equalTo: lv.leadingAnchor, constant: 4).isActive = true
let previousView = lv.subviews[lv.subviews.count-1]
label.topAnchor.constraint(equalTo: previousView.bottomAnchor, constant: 10).isActive = true
return label
}
所有标签都已添加,但约束根本不起作用。下面是它的样子(当我执行上述方法2次时):
编辑:主要问题已解决。我正在使用堆栈视图。()
现在,我希望标签与边之间有偏移,因此我使用这些线:
label.leadingAnchor.constraint(equalTo: lessonStackView.leadingAnchor, constant: offset).isActive = true
label.trailingAnchor.constraint(equalTo: lessonStackView.trailingAnchor, constant: -offset).isActive = true
但由于StackView似乎自己设置了x约束,我得到了以下警告:
无法同时满足约束。
可能下面列表中至少有一个约束是您不想要的。
试试这个:
(1) 看看每一个约束,试着找出你不期望的;
(2) 找到添加了不需要的约束的代码,然后修复它。
(
“UILabel:0x7f9c16c22c30'Falls dir die应用程序gef\U00e4llt…”(活动,名称:“|”):JavaProf.MultipleContentsView:0x7f9c19024a60)>,
"",
""
)
将尝试通过打破约束进行恢复
如何解决此问题?删除
width
锚定。您不应该关心宽度(而且您并不真正了解宽度),而是使用trailingAnchor
:
label.trailingAnchor.constraint(equalTo: lv.trailingAnchor, constant: -4).isActive = true
删除高度锚定,让系统为您计算高度:
label.setContentHuggingPriority(.required, for: .vertical)
label.setContentCompressionResistancePriority(.required, for: .vertical)
这应该是所有需要的
但是,作为旁注,如果要对标签堆栈(或其他视图)使用
UIStackView
,并且希望它们具有不同的前导间距,则可以使用UIStackView
,而不是对上一个标签创建约束,您可以使用UIStackView
1) 将标签嵌入ui视图
。让UIView
填充堆栈视图的宽度,并为视图提供包含的标签约束
2) 将堆栈视图Aligment
设置为Trailing
。然后向每个标签添加宽度约束,该约束等于堆栈视图的宽度。对于希望具有32点“左边距”的标签,请将该标签上的常数设置为-32
下面是一个简单的例子:
class LeftMarginViewController: UIViewController {
let stackView: UIStackView = {
let v = UIStackView()
v.axis = .vertical
v.alignment = .trailing
v.distribution = .fill
v.spacing = 8
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
for i in 1...7 {
let v = UILabel()
v.backgroundColor = .yellow
v.numberOfLines = 0
if i == 5 {
v.text = "Label 5 has a lot of text to demonstrate what happens when it needs to wrap onto multiple lines."
} else {
v.text = "Label \(i)"
}
stackView.addArrangedSubview(v)
switch i {
case 6:
v.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 1.0, constant: -32.0).isActive = true
case 2, 4, 5:
v.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 1.0, constant: -16.0).isActive = true
default:
v.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 1.0, constant: 0.0).isActive = true
}
}
stackView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(stackView)
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
stackView.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0),
stackView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
stackView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
])
}
}
堆栈视图具有对齐:尾部
,每个标签的宽度等于堆栈视图的宽度,标签2、4和5具有常量=-16
,标签6具有常量=-32
结果:
我现在正在使用StackView。我更新了我的问题,如果你再看一眼就好了!如果要从边偏移,只需偏移整个堆栈视图。这是最简单的方法。谢谢,但是偏移量取决于不同的标签,所以在这种情况下我不能这样做。谢谢你的回答。我没有完全使用这种方法,但我将StackView的对齐方式改为居中,而不是填充。现在警告消失了,一切正常
class LeftMarginViewController: UIViewController {
let stackView: UIStackView = {
let v = UIStackView()
v.axis = .vertical
v.alignment = .trailing
v.distribution = .fill
v.spacing = 8
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
for i in 1...7 {
let v = UILabel()
v.backgroundColor = .yellow
v.numberOfLines = 0
if i == 5 {
v.text = "Label 5 has a lot of text to demonstrate what happens when it needs to wrap onto multiple lines."
} else {
v.text = "Label \(i)"
}
stackView.addArrangedSubview(v)
switch i {
case 6:
v.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 1.0, constant: -32.0).isActive = true
case 2, 4, 5:
v.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 1.0, constant: -16.0).isActive = true
default:
v.widthAnchor.constraint(equalTo: stackView.widthAnchor, multiplier: 1.0, constant: 0.0).isActive = true
}
}
stackView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(stackView)
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
stackView.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0),
stackView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
stackView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
])
}
}