为啥 SwiftUI UIHostingController 有额外的间距?

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【中文标题】为啥 SwiftUI UIHostingController 有额外的间距?【英文标题】:Why does SwiftUI UIHostingController have extra spacing?为什么 SwiftUI UIHostingController 有额外的间距? 【发布时间】:2021-12-30 02:29:37 【问题描述】:

我正在尝试使用 UIHostingController 将 SwiftUI 视图添加到 UIKit 视图,它显示了额外的间距(此示例用于模拟生产应用程序上的问题)。这是屏幕截图。

布局概览:

View
  UIStackView
    UIImageView
    UIView(red)
    UIHostingController
    UIView(blue)

问题: swift UI 视图 (UIHostingController) 显示在红色和蓝色视图之间,它在分隔线后显示额外的间距。间距根据 SwiftUI 视图的大小而变化。

如果我减少行数(Hello World 文本)或减少间距,它似乎工作正常。

这里是完整的源代码(https://www.sendspace.com/file/ux0xt7):

ViewController.swift(主视图)

import UIKit

class ViewController: UIViewController 

    @IBOutlet weak var mainStackView: UIStackView!
    
    override func viewDidLoad() 
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        addView()
    


    private func addView() 
        mainStackView.spacing = 0
        mainStackView.alignment = .fill
        
        let imageView = UIImageView()
        imageView.image = UIImage(named: "mountain")
        imageView.contentMode = .scaleAspectFill
        imageView.clipsToBounds = true
        imageView.heightAnchor.constraint(equalToConstant: 260).isActive = true
        mainStackView.addArrangedSubview(imageView)
        
        let redView = UIView()
        redView.backgroundColor = .red
        redView.heightAnchor.constraint(equalToConstant: 100).isActive = true
        mainStackView.addArrangedSubview(redView)
        
        
        
        let sampleVC = SampleViewController()
        //let size = sampleVC.view.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize)
        //sampleVC.view.heightAnchor.constraint(equalToConstant: size.height).isActive = true
        mainStackView.addArrangedSubview(sampleVC.view)
        
        
        let blueView = UIView()
        blueView.backgroundColor = .blue
        blueView.heightAnchor.constraint(equalToConstant: 100).isActive = true
        mainStackView.addArrangedSubview(blueView)
    

SampleView.swift

import SwiftUI

struct SampleView: View 
    var body: some View 
        VStack(spacing: 0) 
            Text("Title")

            VStack (alignment: .leading, spacing: 30) 
                Text("Hello World1")
                Text("Hello World2")
                Text("Hello World3")
                Text("Hello World4")
                Text("Hello World5")
                Text("Hello World6")
                Text("Hello World7")
                Text("Hello World8")
                Text("Hello World9")
                Text("Hello World10")
            
            Divider()
        
        
    




struct SampleView_Previews: PreviewProvider 

    
    static var previews: some View 
        Group 
            SampleView()
        
    

SampleViewController.swift

import UIKit
import SwiftUI

class SampleViewController: UIViewController 
    override func viewDidLoad() 
        super.viewDidLoad()
        
        addView()
    
    
    private func addView() 
        let hostingController = UIHostingController(rootView: SampleView())
        
        hostingController.view.backgroundColor = .clear
        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
        addChild(hostingController)
        view.addSubview(hostingController.view)
        hostingController.didMove(toParent: self)
        
        NSLayoutConstraint.activate([
            hostingController.view.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            hostingController.view.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
            hostingController.view.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 0),
            hostingController.view.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
        ])
    

提前致谢!

【问题讨论】:

它看起来像一个错误 - 托管视图认为它在根目录中并将edgeAreaInsets 应用于内部 SwiftUI 内容。 【参考方案1】:

除了UIView(red),您可以简单地使用Color.redUIView(blue) 相同:

struct SampleView: View 
    var body: some View 
        
        VStack(spacing: .zero) 
            
            Color.red
            
            Text("Title")

            VStack (alignment: .leading, spacing: 30) 
                Text("Hello World1")
                Text("Hello World2")
                Text("Hello World3")
                Text("Hello World4")
                Text("Hello World5")
                Text("Hello World6")
                Text("Hello World7")
                Text("Hello World8")
                Text("Hello World9")
                Text("Hello World10")
            
            
            Divider()
            
            Color.blue.opacity(0.1)
        
 
    


结果:

【讨论】:

这是一个简单的演示应用程序,它从真实应用程序中模拟了问题。如果您将 Color.red 或 blue 视图替换为其他视图(例如图像),您可以很容易地看到布局中断。 我相信您想要的任何东西都可以用红色和蓝色替换,没有任何问题!也许你使用错误的方式! @丹尼 唯一的 swift ui 视图是白色背景的中间视图。上面的红色和蓝色视图是我的示例应用程序中的 UIKit 视图。当 swift ui 视图与滚动视图中的 UIKit 视图混合时,就会发生这种情况。 如果您仅使用少量视图,则不会发生这种情况。 没问题,你的设计和计划是你对可能的东西说不,最好的方法是不使用它或以正确的方式使用它。【参考方案2】:

让宿主控制器的视图再次更新其布局:

class SampleViewController: UIViewController 
    override func viewDidLoad() 
        super.viewDidLoad()
        
        addView()
    
    
    private func addView() 
        let hostingController = UIHostingController(rootView: SampleView())
        
        hostingController.view.backgroundColor = .clear
        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
        addChild(hostingController)
        view.addSubview(hostingController.view)
        hostingController.didMove(toParent: self)
        
        NSLayoutConstraint.activate([
            hostingController.view.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
            hostingController.view.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
            hostingController.view.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 0),
            hostingController.view.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
        ])
        
        hostingController.view.layoutIfNeeded()
    


【讨论】:

它不起作用。 奇怪。你不能只在VStack 的底部添加一个填充而不是使用Divider,或者最终尝试将其包装在AnyView 中,然后在主机控制器中使用它:let hostingController = UIHostingController(rootView: AnyView(SampleView())) 添加分隔线以显示错误造成的额外间距。 @Danny 你试过用AnyView 包装吗? 是的,它不起作用。【参考方案3】:

我遇到了类似的问题,就像 @Asperi mentions,由于 SwiftUI 视图应用了额外的安全区域插图。

很遗憾,简单地将edgesIgnoringSafeArea() 添加到 SwiftUI 视图中是行不通的。

相反,您可以使用以下 UIHostingController 扩展来解决此问题:

extension UIHostingController 
    convenience public init(rootView: Content, ignoreSafeArea: Bool) 
        self.init(rootView: rootView)
        
        if ignoreSafeArea 
            disableSafeArea()
        
    
    
    func disableSafeArea() 
        guard let viewClass = object_getClass(view) else  return 
        
        let viewSubclassName = String(cString: class_getName(viewClass)).appending("_IgnoreSafeArea")
        if let viewSubclass = NSClassFromString(viewSubclassName) 
            object_setClass(view, viewSubclass)
        
        else 
            guard let viewClassNameUtf8 = (viewSubclassName as NSString).utf8String else  return 
            guard let viewSubclass = objc_allocateClassPair(viewClass, viewClassNameUtf8, 0) else  return 
            
            if let method = class_getInstanceMethod(UIView.self, #selector(getter: UIView.safeAreaInsets)) 
                let safeAreaInsets: @convention(block) (AnyObject) -> UIEdgeInsets =  _ in
                    return .zero
                
                class_addMethod(viewSubclass, #selector(getter: UIView.safeAreaInsets), imp_implementationWithBlock(safeAreaInsets), method_getTypeEncoding(method))
            
            
            objc_registerClassPair(viewSubclass)
            object_setClass(view, viewSubclass)
        
    

并像这样使用它:

let hostingController = UIHostingController(rootView: SampleView(), ignoreSafeArea: true)

解决方案出处:https://defagos.github.io/swiftui_collection_part3/#fixing-cell-frames

【讨论】:

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