如何使用顶部布局指南设置布局约束？

Question

代码是:

    [self.view addConstraints: [NSLayoutConstraint constraintsWithVisualFormat: @"V:|-0-[button]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(button)]];

但该视图与superview相关,而不是顶级布局指南.

Answer 1

| 指的是superview,因此您创建的约束将视图固定到superview的顶部.

您需要将顶部布局指南添加为VFL字符串中的项目:

id guide = self.topLayoutGuide;
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[guide][button]"
                  options:0
                  metrics:nil
                    views:NSDictionaryOfVariableBindings(guide,button)]];