当大标题折叠时，如何显示不同的导航标题？

How to present different navigation title when large title collapse?(当大标题折叠时，如何显示不同的导航标题？)

问题描述

目前，我在ViewController的viewdidLoad中使用以下代码为导航栏启用了大标题：

navigationController?.navigationBar.prefersLargeTitles = true
        self.navigationController?.navigationItem.largeTitleDisplayMode = .automatic

        let date = Date()
        let formatter = DateFormatter()
        formatter.dateFormat = "MMMM dd"
        let result = formatter.string(from: date)




        self.title = "VGhpcyBpcyBhIFRlc3QKKHJlc3VsdCk="



        var count = 0
        for item in(self.navigationController?.navigationBar.subviews)! {
            for sub in item.subviews{
                if sub is UILabel{
                    if count == 1 {
                        break;
                    }
                    let titleLab :UILabel = sub as! UILabel
                    titleLab.numberOfLines = 0
                    titleLab.text = self.title
                    titleLab.lineBreakMode = .byWordWrapping
                    count = count + 1
                }
            }

        }
        self.navigationController?.navigationBar.layoutSubviews()
        self.navigationController?.navigationBar.layoutIfNeeded()

在导航栏不再很大的"正常状态"下折叠时，如何显示完全不同的标题？

推荐答案

您可以observebounds更改navigationBar的title，并选中navigationBar的height。

1.对于小标题，navigationBar的height=44

2.对于大标题，navigationBar的height44

class VC: UIViewController {
    var observer: NSKeyValueObservation?

    override func viewDidLoad() {
        super.viewDidLoad()
        self.observer = self.navigationController?.navigationBar.observe(.bounds, options: [.new], changeHandler: { (navigationBar, changes) in
            if let height = changes.newValue?.height {
                if height > 44.0 {
                    //Large Title
                    self.title = "TGFyZ2UgVGl0bGU="
                } else {
                    //Small Title
                    self.title = "U21hbGwgVGl0bGU="
                }
            }
        })
    }
}