Question

那么，我认为以下内容是等效的？

# This is how I usually do
contentView.leftAnchor.constraint(equalTo: leftAnchor, constant: 5).isActive = true
contentView.topAnchor.constraint(equalTo: topAnchor, constant: 5).isActive = true
contentView.rightAnchor.constraint(equalTo: rightAnchor, constant: -5).isActive = true
contentView.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -5).isActive = true

# This is what I tried. I expected the same result..
layoutMargins = UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
contentView.leftAnchor.constraint(equalTo: layoutMarginsGuide.leftAnchor).isActive = true
contentView.topAnchor.constraint(equalTo: layoutMarginsGuide.topAnchor).isActive = true
contentView.rightAnchor.constraint(equalTo: layoutMarginsGuide.rightAnchor).isActive = true
contentView.bottomAnchor.constraint(equalTo: layoutMarginsGuide.bottomAnchor).isActive = true

虽然我看似错了。如何使用边距，约束和锚点获得containerView和父级之间的5个边距？

Answer 1

我通过阅读这个问题找到了解决方案：Auto Layout: layoutMarginsGuide。

从layoutMargins设置init时似乎存在问题。

虽然我没有在layoutMargins中设置viewDidMoveToSuperView，而是将其放在updateConstraints中，而且工作正常。

所以代码现在是：

override init(frame: CGRect) {
    super.init(frame: frame)
    contentView.leftAnchor.constraint(equalTo: layoutMarginsGuide.leftAnchor).isActive = true
    contentView.topAnchor.constraint(equalTo: layoutMarginsGuide.topAnchor).isActive = true
    contentView.rightAnchor.constraint(equalTo: layoutMarginsGuide.rightAnchor).isActive = true
    contentView.bottomAnchor.constraint(equalTo: layoutMarginsGuide.bottomAnchor).isActive = true
}

override func updateConstraints() {
    super.updateConstraints()
    layoutMargins = UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
}

然后具有与以下相同的效果：

contentView.leftAnchor.constraint(equalTo: leftAnchor, constant: 5).isActive = true
contentView.topAnchor.constraint(equalTo: topAnchor, constant: 5).isActive = true
contentView.rightAnchor.constraint(equalTo: rightAnchor, constant: -5).isActive = true
contentView.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -5).isActive = true

Answer 2

似乎在layoutMargins中设置updateConstraints()有效，但有以下警告：

override func updateConstraints() {
    super.updateConstraints()
    layoutMargins = UIEdgeInsets(top: 8, left: 8, bottom: 8, right: 8)
}

上述代码无法更新边距，因为新值与系统默认值相同。所以为了安全起见，首先将边距重置为零：

override func updateConstraints() {
    super.updateConstraints()
    layoutMargins = .zero
    layoutMargins = UIEdgeInsets(top: 8, left: 8, bottom: 8, right: 8)
}

此外，如果您的目标是将初始边距设置为.zero，那么首先将它们设置为非零值可能是个好主意，只是为了确保视图会通知更改。 / p>

Answer 3

目标-C：

[contentView.leftAnchor constraintEqualToAnchor:contentView.superview.leftAnchor constant:5].active = YES;
[contentView.rightAnchor constraintEqualToAnchor:contentView.superview.rightAnchor constant:5].active = YES;
[contentView.topAnchor constraintEqualToAnchor:contentView.superview.topAnchor constant:5].active = YES;
[contentView.bottomAnchor constraintEqualToAnchor:contentView.superview.bottomAnchor constant:5].active = YES;

斯威夫特3：

contentView.leftAnchor.constraint(equalTo: contentView.superview?.leftAnchor, constant: 5).isActive = true
contentView.rightAnchor.constraint(equalTo: contentView.superview?.rightAnchor, constant: 5).isActive = true
contentView.topAnchor.constraint(equalTo: contentView.superview?.topAnchor, constant: 5).isActive = true
contentView.bottomAnchor.constraint(equalTo: contentView.superview?.bottomAnchor, constant: 5).isActive = true

使用锚点自动布局边距

3 个答案: