视图高度意外更改（Swift）

Question

我已经设置了约束，允许 UIView cv1 根据屏幕大小动态改变高度，cv2 和 cv3 的高度是固定的。

由于某种原因，当我如图所示运行时，cv3 的视图高度变为 172。

在一个或另一个或两个中使用原始的cv3.heightAnchor.constraint(equalToConstant: cv3Height)，我遇到了与here 相同的问题（这对cv2 非常有效），附加效果是我用h3, 替换它（窄或宽）视图仅在该方向跳转到 172，但也给了我冲突约束消息。

没有运气，我删除了所有其他约束。

这是另一个错误吗？如果是这样，是否有解决方法？

这里是一个最小化的函数，整个函数如下：

func setConstraints() {
            
    cv3.translatesAutoresizingMaskIntoConstraints = false

    let g = view.safeAreaLayoutGuide
    
    let cv3Height: CGFloat = 125
    let h3 = cv3.heightAnchor.constraint(equalToConstant: cv3Height)
    h3.priority = .defaultHigh
    
    narrowConstraints = [
        // set cv3 height
        //cv3.heightAnchor.constraint(equalToConstant: cv3Height),
        h3, 

        // lock left, right and bottom to safe area
        cv3.leadingAnchor.constraint(equalTo: g.leadingAnchor),
        cv3(equalTo: g.trailingAnchor),
        cv3(equalTo: g.bottomAnchor),
    ]
    
    wideConstraints = [
        // set cv3 height
        //cv3.heightAnchor.constraint(equalToConstant: cv3Height),
        h3, 

        // lock bottom and right side of cv3 to safe area
        cv3(equalTo: g.trailingAnchor),
        cv3(equalTo: g.bottomAnchor),
        
        // make them all equal widths
        cv2.widthAnchor.constraint(equalTo: cv1.widthAnchor),
        cv3.widthAnchor.constraint(equalTo: cv2.widthAnchor),
    ]

    
    // activate the commonConstraints
    NSLayoutConstraint.activate(commonConstraints)
    
    if view.frame.width > view.frame.height {
        // wider than tall, so "landscape"
        NSLayoutConstraint.deactivate(narrowConstraints)
        NSLayoutConstraint.activate(wideConstraints)
    } else {
        // taller than wide
        NSLayoutConstraint.deactivate(wideConstraints)
        NSLayoutConstraint.activate(narrowConstraints)
    }
    
}

这是整个函数：

func setConstraints() {
    
    cv1.translatesAutoresizingMaskIntoConstraints = false
    cv2.translatesAutoresizingMaskIntoConstraints = false
    cv3.translatesAutoresizingMaskIntoConstraints = false
    
    let g = view.safeAreaLayoutGuide
    
    let cv2Height: CGFloat = 190
    let h2 = cv2.heightAnchor.constraint(equalToConstant: cv2Height)
    h2.priority = .defaultHigh
    
    let cv3Height: CGFloat = 125
    let h3 = cv3.heightAnchor.constraint(equalToConstant: cv3Height)
    h3.priority = .defaultHigh
    
    narrowConstraints = [
        
        // lock top, left and right to safe area
        cv1.topAnchor.constraint(equalTo: g.topAnchor),
        cv1.leadingAnchor.constraint(equalTo: g.leadingAnchor),
        cv1.trailingAnchor.constraint(equalTo: g.trailingAnchor),
        
        // set cv2 height
        //cv2.heightAnchor.constraint(equalToConstant: cv2Height),
        h2,

        // lock left and right to safe area
        cv2.leadingAnchor.constraint(equalTo: g.leadingAnchor),
        cv2.trailingAnchor.constraint(equalTo: g.trailingAnchor),
        
        // lock top of cv2 to bottom of cv1
        cv2.topAnchor.constraint(equalTo: cv1.bottomAnchor),
        // lock bottom of cv2 to top of cv3
        cv2.bottomAnchor.constraint(equalTo: cv3.topAnchor),
        
        // set cv3 height
        //cv3.heightAnchor.constraint(equalToConstant: cv3Height),
        h3, 

        // lock left, right and bottom to safe area
        cv3.leadingAnchor.constraint(equalTo: g.leadingAnchor),
        cv3(equalTo: g.trailingAnchor),
        cv3(equalTo: g.bottomAnchor),
    ]
    
    wideConstraints = [
        
        // lock top, bottom, and left to safe area
        cv1.topAnchor.constraint(equalTo: g.topAnchor),
        cv1.bottomAnchor.constraint(equalTo: g.bottomAnchor),
        cv1.leadingAnchor.constraint(equalTo: g.leadingAnchor),
        // lock right side of cv1 to left side of cv2
        cv1.trailingAnchor.constraint(equalTo: cv2.leadingAnchor),
        
        // lock right side of cv2 to safe area
        cv2.trailingAnchor.constraint(equalTo: g.trailingAnchor),
        // lock top of cv2 to safe area
        cv2.topAnchor.constraint(equalTo: g.topAnchor),
        // lock bottom of cv2 to top of cv3
        cv2.bottomAnchor.constraint(equalTo: cv3.topAnchor),
        
        // set cv3 height
        //cv3.heightAnchor.constraint(equalToConstant: cv3Height),
        h3, 

        // lock bottom and right side of cv3 to safe area
        cv3(equalTo: g.trailingAnchor),
        cv3(equalTo: g.bottomAnchor),
        
        // make them all equal widths
        cv2.widthAnchor.constraint(equalTo: cv1.widthAnchor),
        cv3.widthAnchor.constraint(equalTo: cv2.widthAnchor),
    ]

    
    // activate the commonConstraints
    NSLayoutConstraint.activate(commonConstraints)
    
    if view.frame.width > view.frame.height {
        // wider than tall, so "landscape"
        NSLayoutConstraint.deactivate(narrowConstraints)
        NSLayoutConstraint.activate(wideConstraints)
    } else {
        // taller than wide
        NSLayoutConstraint.deactivate(wideConstraints)
        NSLayoutConstraint.activate(narrowConstraints)
    }
    
}

Answer 1

我看起来问题是每次调用函数时，您都在创建新的约束，但没有停用上次运行时的旧约束。

例如，第一次调用它时，它将创建一组宽和窄约束并激活宽集。下次调用它时，它将创建一组新的宽约束和窄约束，并激活第二组的窄约束，而不会停用第一组的宽约束。您对停用它的调用将在第二组上调用，这将生效。

我猜想冲突约束消息显示了第一组中尚未停用的约束。

---

我要做的是将你的函数分成两个单独的函数。

创建一个setupConstraints 函数，该函数仅创建约束数组并仅激活commonConstraints。重要的部分是确保这个函数只被调用一次。

创建一个 activateConstraintsForOrientation 函数，该函数仅在函数底部包含 if 语句。然后，只要您认为方向发生了变化，就可以调用此函数。