Swift中如何在父ScrollView中设置子ViewController容器高度并适配滚动内容

第一步：子VC侧的自计算高度适配 #

• 给每个子VC新增公开只读属性contentHeight，直接返回自身内容总高度，你可以直接复用原ScrollView移除前记录的contentSize.height，也可以通过子视图实时计算：

// Swift示例
var contentHeight: CGFloat {
    // 取所有子视图的最大下边缘作为内容总高度
    return view.subviews.reduce(0) { max($0, $1.frame.maxY) }
}

• 确保子VC主视图没有固定高度约束，所有子控件的上下约束完整，可通过子视图撑出主视图的实际高度。

第二步：父VC侧推荐用Auto Layout实现（无需手动计算contentSize） #

• 先给父VC添加统一的滚动容器，铺满父视图：

let parentScrollView = UIScrollView()
parentScrollView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(parentScrollView)
NSLayoutConstraint.activate([
    parentScrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
    parentScrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
    parentScrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
    parentScrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
])

• 给滚动容器添加contentView，用于自动撑出滚动范围：

let contentView = UIView()
contentView.translatesAutoresizingMaskIntoConstraints = false
parentScrollView.addSubview(contentView)
NSLayoutConstraint.activate([
    // 绑定contentView和scrollView的content布局 Guide
    contentView.topAnchor.constraint(equalTo: parentScrollView.contentLayoutGuide.topAnchor),
    contentView.leadingAnchor.constraint(equalTo: parentScrollView.contentLayoutGuide.leadingAnchor),
    contentView.trailingAnchor.constraint(equalTo: parentScrollView.contentLayoutGuide.trailingAnchor),
    contentView.bottomAnchor.constraint(equalTo: parentScrollView.contentLayoutGuide.bottomAnchor),
    // 固定contentView宽度和scrollView一致，仅支持垂直滚动
    contentView.widthAnchor.constraint(equalTo: parentScrollView.widthAnchor)
])

• 添加两个子VC的容器视图，垂直排列，高度直接绑定子VC的内容高度：

// 容器A对应子VC A
let containerA = UIView()
containerA.translatesAutoresizingMaskIntoConstraints = false
contentView.addSubview(containerA)
addChild(vcA)
vcA.view.translatesAutoresizingMaskIntoConstraints = false
containerA.addSubview(vcA.view)
NSLayoutConstraint.activate([
    vcA.view.topAnchor.constraint(equalTo: containerA.topAnchor),
    vcA.view.leadingAnchor.constraint(equalTo: containerA.leadingAnchor),
    vcA.view.trailingAnchor.constraint(equalTo: containerA.trailingAnchor),
    vcA.view.bottomAnchor.constraint(equalTo: containerA.bottomAnchor)
])
vcA.didMove(toParent: self)
// 容器B对应子VC B，实现逻辑同上
let containerB = UIView()
containerB.translatesAutoresizingMaskIntoConstraints = false
contentView.addSubview(containerB)
addChild(vcB)
vcB.view.translatesAutoresizingMaskIntoConstraints = false
containerB.addSubview(vcB.view)
NSLayoutConstraint.activate([
    vcB.view.topAnchor.constraint(equalTo: containerB.topAnchor),
    vcB.view.leadingAnchor.constraint(equalTo: containerB.leadingAnchor),
    vcB.view.trailingAnchor.constraint(equalTo: containerB.trailingAnchor),
    vcB.view.bottomAnchor.constraint(equalTo: containerB.bottomAnchor)
])
vcB.didMove(toParent: self)
// 垂直排列两个容器，绑定高度
let containerAHeightConstraint = containerA.heightAnchor.constraint(equalToConstant: vcA.contentHeight)
let containerBHeightConstraint = containerB.heightAnchor.constraint(equalToConstant: vcB.contentHeight)
NSLayoutConstraint.activate([
    containerA.topAnchor.constraint(equalTo: contentView.topAnchor),
    containerA.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
    containerA.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
    containerAHeightConstraint,
    
    containerB.topAnchor.constraint(equalTo: containerA.bottomAnchor),
    containerB.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
    containerB.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
    containerB.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
    containerBHeightConstraint
])

注意：该方案下父ScrollView的contentSize会通过contentView的约束自动计算，无需手动赋值。

第三步：动态内容更新处理 #

如果子VC的内容会动态变化（比如异步加载数据后更新视图），子VC内容更新后主动触发父VC更新容器高度即可：

// 子VC内容更新后调用该回调
vcA.onContentChanged = { [weak self] newHeight in
    guard let self = self else { return }
    self.containerAHeightConstraint.constant = newHeight
    UIView.animate(withDuration: 0.2) {
        self.view.layoutIfNeeded()
    }
}

可选：Frame布局方案的处理 #

如果你坚持用frame布局，可按以下逻辑计算：

• 子VC布局完成后，调用systemLayoutSizeFitting获取实际高度：

let targetSize = CGSize(width: parentScrollView.bounds.width, height: UIView.layoutFittingCompressedSize.height)
let vcAHeight = vcA.view.systemLayoutSizeFitting(targetSize).height
containerA.frame = CGRect(x: 0, y: 0, width: parentScrollView.bounds.width, height: vcAHeight)
let vcBHeight = vcB.view.systemLayoutSizeFitting(targetSize).height
containerB.frame = CGRect(x: 0, y: vcAHeight, width: parentScrollView.bounds.width, height: vcBHeight)
// 手动更新父ScrollView的contentSize
parentScrollView.contentSize = CGSize(width: parentScrollView.bounds.width, height: vcAHeight + vcBHeight)

• 子VC内容更新时，重新执行上述计算逻辑，更新container的frame和scrollView的contentSize即可。

内容的提问来源于stack exchange，提问作者Vinoth Kumar