子视图控制器和边距

Question

我有一个如下的子视图控制器。

import UIKit
class SampleChildViewController : UIViewController {

    let imageView : UIImageView = {
        let imageview = UIImageView()
        imageview.translatesAutoresizingMaskIntoConstraints = false
        imageview.clipsToBounds = true
        imageview.contentMode = .scaleAspectFit
        imageview.image = UIImage(named: "cat")
        return imageview
    }()


    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(imageView)

        NSLayoutConstraint.activate([
            imageView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 8),
            imageView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 8),
            imageView.widthAnchor.constraint(equalToConstant: 150),
            imageView.heightAnchor.constraint(equalToConstant: 150)
            ])
    }


}

然后我有如下所示的父视图控制器。我已将子视图控制器添加到父视图控制器中，如下所示。

import UIKit

class ViewController: UIViewController {

    let child : SampleChildViewController = SampleChildViewController()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.white
        child.view.translatesAutoresizingMaskIntoConstraints = false
        addChild(child)
        view.addSubview(child.imageView)
        child.didMove(toParent: self)

    }


}

现在问题是我在图像视图的父视图控制器中有一个奇怪的边距问题。如下面的屏幕快照所示，图像视图隐藏在导航栏的后面。如果我将子视图控制器作为根视图控制器并加载应用程序，则图像视图将正确定位。如何解决这个问题？

Answer 1

您既不给子视图一个框架，也不给它一个约束

child.view.translatesAutoresizingMaskIntoConstraints = false 

还应该添加视图而不是imageView

view.addSubview(child.view) 
NSLayoutConstraint.activate([
   child.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 8),
   child.view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 8),
   child.view.leftAnchor.constraint(equalTo: view.leftAnchor),
   child.view.rightAnchor.constraint(equalTo: view.rightAnchor),
])

并设置

navigationController?.navigationBar.prefersLargeTitles = false