ios - swift 自动布局 : constraints in sub-view not working

Question

我正在尝试设置一个 View ，其中包含两个 Collection View 和一个位于中心的 View ，而中心 View 又包含元素。

我一直在尝试使用这样的视觉格式设置约束:

func setupViews() {

    self.view.addSubview(playGroundView)
    self.view.addSubview(firstCollectionView)
    self.view.addSubview(secondCollectionView)

    self.playGroundView.backgroundColor = UIColor.clear


    aTextView.backgroundColor = UIColor.yellow
    titleTextView.backgroundColor = UIColor.green
    searchBar?.backgroundColor = UIColor.darkGray


    if #available(iOS 9.0, *) {
        playGroundView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
        firstCollectionView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
        secondCollectionView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
    } else {
        // Fallback on earlier versions
    }

    self.playGroundView.addSubview(publishButton)
    self.playGroundView.addSubview(searchBar!)
    self.playGroundView.addSubview(aTextView)
    self.playGroundView.addSubview(titleTextView)

    publishButton.addConstraint(NSLayoutConstraint(item: publishButton, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 44))
    aTextView.addConstraint(NSLayoutConstraint(item: aTextView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 44))
    titleTextView.addConstraint(NSLayoutConstraint(item: titleTextView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 44))
    searchBar!.addConstraint(NSLayoutConstraint(item: searchBar!, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 44))

    self.playGroundView.addConstraintsWithFormat("V:[v0]-2-|", views: publishButton)
    self.playGroundView.addConstraintsWithFormat("H:[v0]-2-|", views: publishButton)
    self.playGroundView.addConstraintsWithFormat("V:|-2-[v0(44)]", views: searchBar!)


    self.view.bringSubview(toFront: aTextView)

    self.playGroundView.layoutIfNeeded()
    self.playGroundView.layoutSubviews()

    self.view.addConstraintsWithFormat("H:|-8-[v0(100)][v1][v2(100)]-8-|", views: secondCollectionView,playGroundView,firstCollectionView)

    self.view.addConstraintsWithFormat("V:[v0]-2-|", views: playGroundView)
    self.view.addConstraintsWithFormat("V:[v0]-2-|", views: secondCollectionView)
    self.view.addConstraintsWithFormat("V:[v0]-2-|", views: firstCollectionView)



    if(self.isCreate){
        self.titleTextView.text = self.recipeDictionary?.value(forKey: "recipeName") as! String!
    }
}


// Function to set constraints

 func addConstraintsWithFormat(_ format: String, views: UIView...) {

        var viewsDictionary = [String: UIView]()
        for (index,view) in views.enumerated() {
            let key = "v\(index)"
            viewsDictionary[key] = view
            view.translatesAutoresizingMaskIntoConstraints = false
        }
        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: format, options: NSLayoutFormatOptions(), metrics: nil, views: viewsDictionary))
    }

我没有看到正在渲染的 subview (playGroundView) 内的元素。有人可以建议我在这里做错了什么吗？

Answer 1

我会尝试以下调试:

1. 临时为 playGroundView 设置纯色背景色而不是 UIColor.clear 并运行它以使 playGroundView 具有正确的大小和位置。
2. 临时为缺失的 subview 设置边框并运行它以查看 View 是否在 playGroundView 边界内。或者，您也可以运行代码，转到 Xcode > Debug > View Debugging > Capture View Hierarchy
3. 在添加到 playGroundView 之前，为 publishButton、searchBar 等设置 translatesAutoresizingMaskIntoConstraints = false。虽然在您的辅助函数 addConstraintsWithFormat 中执行该操作并没有错，但没有必要多次进行该调用。