iOS 17下UIBarButtonItem的pulse符号动画失效问题（不使用UIImageView）

你的代码逻辑本身没问题，但符号动画的添加时机不对——在viewDidLoad阶段，UIBarButtonItem尚未被添加到实际视图层级中，此时调用addSymbolEffect不会触发动画效果。WWDC视频的描述没错，但未强调这个关键的时机细节。

修正方案：调整动画添加时机 #

把添加符号动画的代码移到按钮完成视图渲染之后执行，有两种可行方式：

方式1：在viewDidAppear中添加动画 #

import UIKit

class ViewController: UIViewController {
    private var resumeButton: UIBarButtonItem?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let config = UIImage.SymbolConfiguration(scale: UIImage.SymbolScale.large)
        let image = UIImage(systemName: "playpause.fill", withConfiguration: config)
        
        resumeButton = UIBarButtonItem(image: image, style: .plain, target: self, action: #selector(sayHello))
        toolbarItems = [resumeButton!]
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        resumeButton?.addSymbolEffect(.pulse, options: .repeating, animated: true)
        resumeButton?.isSymbolAnimationEnabled = true
    }
    
    @objc func sayHello(_ sender: UIBarButtonItem) {
        print("Hello: \(sender)")
    }
}

方式2：在viewDidLoad中延迟执行动画 #

通过DispatchQueue.main.async把动画代码推迟到下一次主循环，确保按钮已加入视图层级：

override func viewDidLoad() {
    super.viewDidLoad()
    
    let config = UIImage.SymbolConfiguration(scale: UIImage.SymbolScale.large)
    let image = UIImage(systemName: "playpause.fill", withConfiguration: config)
    
    let resumeButton = UIBarButtonItem(image: image, style: .plain, target: self, action: #selector(sayHello))
    toolbarItems = [resumeButton]
    
    // 延迟执行，确保按钮完成渲染
    DispatchQueue.main.async {
        resumeButton.addSymbolEffect(.pulse, options: .repeating, animated: true)
        resumeButton.isSymbolAnimationEnabled = true
    }
}

关于自定义UIImageView的对齐问题 #

如果你想通过自定义视图实现动画，别直接用UIImageView作为customView，改用UIButton包裹UIImageView——UIButton会自动适配工具栏的布局规则，解决尺寸和对齐异常的问题：

override func viewDidLoad() {
    super.viewDidLoad()
    
    let config = UIImage.SymbolConfiguration(scale: UIImage.SymbolScale.large)
    let image = UIImage(systemName: "playpause.fill", withConfiguration: config)
    
    // 用UIButton包裹UIImageView，自动适配工具栏布局
    let button = UIButton(type: .system)
    button.setImage(image, for: .normal)
    button.addTarget(self, action: #selector(sayHello), for: .touchUpInside)
    
    // 给内部的UIImageView添加符号动画
    if let imageView = button.imageView {
        imageView.addSymbolEffect(.pulse, options: .repeating, animated: true)
    }
    
    let resumeButton = UIBarButtonItem(customView: button)
    toolbarItems = [resumeButton]
}

内容的提问来源于stack exchange，提问作者Mario