ios - 以编程方式设置一组 View 的布局约束

Question

我有三个 UIImageView(水平并排放置)，我想在 self.view 内水平和垂直居中，它们之间的水平间距固定他们。我不太了解布局约束的使用，我知道将它们放入中间容器中然后适当设置 autoresizingMask 就可以解决问题:

containerView.autoresizingMask = UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin;

如果不使用中间容器，要达到同样的效果需要什么？

Answer 1

假设您的 View 中有 ImageView leftImageView、rightImageView 和 centerImageView，这些约束应该可以解决问题:

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:centerImageView
                                                      attribute:NSLayoutAttributeCenterX
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:self.view
                                                      attribute:NSLayoutAttributeCenterX
                                                     multiplier:1
                                                       constant:0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:centerImageView
                                                      attribute:NSLayoutAttributeCenterY
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:self.view
                                                      attribute:NSLayoutAttributeCenterY
                                                     multiplier:1
                                                       constant:0]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"[leftImage]-[centerImage]-[rightImage]"
                                                                  options:NSLayoutFormatAlignAllCenterY
                                                                  metrics:nil
                                                                    views:@{@"leftImage" : leftImageView,
                                                                            @"rightImage" : rightImageView,
                                                                            @"centerImage" : centerImageView}]];

确保 translatesAutoresizingMaskIntoConstraints 在每个 ImageView 上都是 false。