iOS开发：合并两个ViewController视图未正常渲染问题求助

问题根源 #

• 仅将子ViewController的view添加到父视图，但未将子VC注册为CommonViewController的子控制器，导致子VC的生命周期方法（如viewDidLoad、viewWillAppear）无法正常触发，视图内容无法渲染。
• 添加子view后未设置任何布局约束，系统无法确定子view的位置和尺寸，因此出现约束错误。

解决方案 #

步骤1：将子VC注册为子控制器

在combineView方法中，创建子VC后必须调用addChild(_:)完成注册，添加view后调用didMove(toParent:)通知子VC完成挂载：

private func combineView() {
    let dvc = MovieDetailsViewController(viewModel: viewModel)
    let svc = SmiliarMovieViewController(viewModel: viewModel)
    
    // 注册子控制器
    addChild(dvc)
    addChild(svc)
    
    view.addSubview(dvc.view)
    view.addSubview(svc.view)
    
    // 通知子VC完成挂载
    dvc.didMove(toParent: self)
    svc.didMove(toParent: self)
    
    // 调用约束设置方法
    setupSubviewConstraints(dvc: dvc, svc: svc)
}

步骤2：添加布局约束

新增私有方法setupSubviewConstraints，给两个子view设置明确的布局规则（示例为垂直上下排列，可根据需求调整）：

private func setupSubviewConstraints(dvc: MovieDetailsViewController, svc: SmiliarMovieViewController) {
    // 关闭自动约束转换，启用手动约束
    dvc.view.translatesAutoresizingMaskIntoConstraints = false
    svc.view.translatesAutoresizingMaskIntoConstraints = false
    
    NSLayoutConstraint.activate([
        // 详情视图：顶部、左右对齐父视图安全区，高度占屏幕1/3
        dvc.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
        dvc.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        dvc.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        dvc.view.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 1/3),
        
        // 相似电影视图：顶部接详情视图底部，左右、底部对齐父视图安全区
        svc.view.topAnchor.constraint(equalTo: dvc.view.bottomAnchor),
        svc.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        svc.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        svc.view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
    ])
}

完整修改后的CommonViewController代码 #

import UIKit

class CommonViewController: UIViewController {
    
    private let viewModel: MoviesDetailsViewModel

    init(viewModel: MoviesDetailsViewModel) {
        self.viewModel = viewModel
        super.init(nibName: nil, bundle: nil)
        navigationItem.largeTitleDisplayMode = .never
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        combineView()
        navigationItem.leftBarButtonItem = UIBarButtonItem.backButton(target: self, action: #selector(didTapBack(_:)))
    }
    
    private func combineView() {
        let dvc = MovieDetailsViewController(viewModel: viewModel)
        let svc = SmiliarMovieViewController(viewModel: viewModel)
        
        addChild(dvc)
        addChild(svc)
        
        view.addSubview(dvc.view)
        view.addSubview(svc.view)
        
        dvc.didMove(toParent: self)
        svc.didMove(toParent: self)
        
        setupSubviewConstraints(dvc: dvc, svc: svc)
    }
    
    private func setupSubviewConstraints(dvc: MovieDetailsViewController, svc: SmiliarMovieViewController) {
        dvc.view.translatesAutoresizingMaskIntoConstraints = false
        svc.view.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            dvc.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
            dvc.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            dvc.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            dvc.view.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 1/3),
            
            svc.view.topAnchor.constraint(equalTo: dvc.view.bottomAnchor),
            svc.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            svc.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            svc.view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
        ])
    }
    
    @objc private func didTapBack(_ sender: UIBarButtonItem) {
        navigationController?.popViewController(animated: true)
    }
}

内容的提问来源于stack exchange，提问作者user23454452