UIScrollView 遇到了AutoLayout之後其contentSize 的計算

UIScrollView 的特殊之處就在於當它遇到了AutoLayout之後其contentSize 的計算規則有些特殊。
contentSize是根據子視圖的leading/trailing/top/bottom進行確定的

所以避免我們手動去設置 contentSize，我們必須迎合它的規則去設置

       let scrollView = UIScrollView()
        
        scrollView.backgroundColor = .gray
        view.addSubview(scrollView)
        scrollView.snp.makeConstraints { (make) in
            make.edges.equalToSuperview()
        }
        let containerView = UIView()
        containerView.backgroundColor = .blue
        scrollView.addSubview(containerView)
        containerView.snp.makeConstraints { (make) in
            make.edges.equalToSuperview()
            make.width.equalToSuperview()
        }
        
        let view1 = UIView()
        view1.backgroundColor = .orange
        
        let view2 = UIView()
        view2.backgroundColor = .blue
        
        
        containerView.addSubview(view1)
        containerView.addSubview(view2)
        
        view1.snp.makeConstraints { (make) in
            make.top.equalToSuperview()
            make.width.equalToSuperview()
            make.height.equalTo(500)
        }
        
        view2.snp.makeConstraints { (make) in
            make.top.equalTo(view1.snp.bottom)
            make.bottom.equalTo(containerView.snp.bottom)
            make.leading.trailing.equalTo(containerView)
            make.width.equalToSuperview()
            make.height.equalTo(500)
        }

大概就是這意思，我們通過一個填滿的 containerView 去設置子視圖，同時我們最後一個 subview 的 bottom 一定要與 containerView 對齊即可

來源https://segmentfault.com/a/1190000037456477