ios - 多个navigationItem.rightBarButtonItem时，navigationItem.titleView无法居中渲染？

Question

我在做this教程。由于 this，我必须修复我的代码问题。导航栏呈现如下图。我只需要我的标题图标位于导航栏的中心。有什么技巧吗？

这是我当前的代码。

func setUpNavigationBarItems(){
    //https://www.youtube.com/watch?v=zS-CCd4xmRY
    let titleImageView = UIImageView(image: UIImage(named: "ic_nav_app_icon"))
    titleImageView.frame = CGRect(x: 0, y: 0, width: 34, height: 34)
    titleImageView.contentMode = .scaleAspectFit
    navigationItem.titleView = titleImageView


    let addButton = UIButton(type: .system)
    let addImage = UIImage(named: "ic_nav_add")
    addButton.setImage(addImage?.withRenderingMode(.alwaysOriginal), for: .normal)
    NSLayoutConstraint(item: addButton, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true
    NSLayoutConstraint(item: addButton, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true
    navigationItem.leftBarButtonItem = UIBarButtonItem(customView: addButton)


    let searchButton = UIButton(type: .system)
    let searchImage = UIImage(named: "ic_nav_phone")
    searchButton.setImage(searchImage?.withRenderingMode(.alwaysOriginal), for: .normal)
    NSLayoutConstraint(item: searchButton, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true
    NSLayoutConstraint(item: searchButton, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true

    let settingButton = UIButton(type: .system)
    let settingImage = UIImage(named: "ic_nav_setting")
    settingButton.setImage(settingImage?.withRenderingMode(.alwaysOriginal), for: .normal)
    NSLayoutConstraint(item: settingButton, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true
    NSLayoutConstraint(item: settingButton, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 30).isActive = true

    navigationItem.rightBarButtonItems = [UIBarButtonItem(customView: searchButton), UIBarButtonItem(customView: settingButton)]

    navigationController?.navigationBar.backgroundColor = .white

}

Answer 1

如果你替换它应该有正确的布局:

titleImageView.frame = CGRect(x: 0, y: 0, width: 34, height: 34)

与:

NSLayoutConstraint(item: titleImageView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 34).isActive = true
NSLayoutConstraint(item: titleImageView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 34).isActive = true

如前一个答案中所述，标题 View 的框架在运行时可能不是 34x34。相反，它部分取决于图像的大小(UIImageView 的固有内容大小取决于图像的大小)和 UINavigationBar 的自动布局配置。

如果您运行 View 调试器，您可能会看到标题 View 的框架类似于 150x44，这就是为什么它被偏移到一侧以便为 UINavigationBar 中的所有内容腾出空间。

View 调试工具位于 Xcode 的底部栏中(在调试区域的顶部):

它可以让您检查框架、约束和更多的 View 层次结构，并且通常会提示您在遇到此类问题时可能出了什么问题。