ios - ios自动布局覆盖另一个视图边缘的视图（分层），以编程方式

Question

在这里，我设计了一个自定义箭头，该箭头将用作共享按钮。它应该被固定在下边缘，如图所示，它的中心点被锚定到底部视图。

我将如何使用 VFL 做到这一点？

这就是我尝试的

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[_whiteSquare(160)]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:elementDict]];


[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[_shareButton(45)]-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:elementDict]];


[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[_shareButton(45)]-20-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:elementDict]];



[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[_whiteSquare]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:elementDict]];

其中whiteSquare和shareButton都附加到超级视图中。但这只是放在shareButton超级视图的底部，而不是中心锚定到 whiteSquare 的底部

Answer 1

您应该相对于白色方块而不是超级视图定位共享按钮

这应该可以解决问题：

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[_whiteSquare(160)]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:elementDict]];


[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[_whiteSquare]-22.5-[_shareButton(45)]"
                                                                  options: NSLayoutFormatDirectionRightToLeft
                                                                  metrics:nil
                                                                    views:elementDict]];


[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[_whiteSquare]-10-|"
                                                                  options:NSLayoutFormatDirectionLeadingToTrailing
                                                                  metrics:nil
                                                                    views:elementDict]];

[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[_whiteSquare]-22.5-[_shareButton(45)]"
                                                                  options:NSLayoutFormatDirectionRightToLeft
                                                                  metrics:nil
                                                                    views:elementDict]];