SwiftUI中UIActivityController无法显示打印图片问题排查

你错误地将UIActivityViewController的SwiftUI包装器放在了sheet中展示。sheet是SwiftUI用于展示自定义SwiftUI视图的容器，而UIActivityViewController是UIKit体系下的模态视图控制器，需要通过UIKit的present方法触发，直接嵌套在sheet里会导致系统无法正确加载分享内容，最终显示空白面板。

通过获取当前活跃的UIKit视图控制器，直接present分享面板，无需依赖SwiftUI的sheet：

1. 添加工具扩展获取当前视图控制器：

extension UIApplication {
    static func currentViewController() -> UIViewController? {
        let keyWindow = shared.connectedScenes
            .filter { $0.activationState == .foregroundActive }
            .compactMap { $0 as? UIWindowScene }
            .first?
            .windows
            .first { $0.isKeyWindow }
        
        return keyWindow?.rootViewController?.presentedViewController ?? keyWindow?.rootViewController
    }
}

2. 修改ContentView的按钮逻辑：

struct ContentView: View {
    var body: some View {
        NavigationStack {
            Text("Hello, World!")
            
            VStack {
                Button(action: {
                    guard let image = UIImage(named: "profile") else {
                        print("Image not found")
                        return
                    }
                    let activityVC = UIActivityViewController(activityItems: [image], applicationActivities: nil)
                    if let currentVC = UIApplication.currentViewController() {
                        currentVC.present(activityVC, animated: true)
                    }
                }, label: {
                    Text("Print")
                })
            }
        }
    }
}

如果你的应用只需要支持iOS 16及以上版本，可以直接使用SwiftUI原生的ShareLink，代码更简洁：

struct ContentView: View {
    private var shareImage: UIImage? {
        UIImage(named: "profile")
    }
    
    var body: some View {
        NavigationStack {
            Text("Hello, World!")
            
            VStack {
                if let image = shareImage {
                    ShareLink(
                        item: image,
                        preview: SharePreview("Profile Image", image: image)
                    ) {
                        Text("Print")
                    }
                } else {
                    Text("Image not found")
                }
            }
        }
    }
}

内容的提问来源于stack exchange，提问作者iosdev1111