iOS开发之Context Menus

介绍

• WWDC 2019 推出了上下文菜单（Context Menus）成为 3DTouch 的替代品。
• 需要通过长按方式触发。
• 如果要启用上下文菜单，需要创建一个 UIContextMenuInteraction 并将其添加给某个触发的 UIView，然后指定 delegate，实现代理方法。
• 代理方法需要返回一个UIContextMenuConfiguration，其构造函数如下init(identifier: NSCopying?, previewProvider: UIContextMenuContentPreviewProvider?, actionProvider: UIContextMenuActionProvider? = nil)，最主要是第三个参数，需要在其中创建UIMenu。
• 案例

class ViewController: UIViewController {

    // 需要打开User Interaction
    @IBOutlet weak var imageView: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // 创建UIContextMenuInteraction
        let interaction = UIContextMenuInteraction(delegate: self)
        // 添加UIContextMenuInteraction
        imageView.addInteraction(interaction)
    }
}

// 代理方法
extension ViewController: UIContextMenuInteractionDelegate {
    func contextMenuInteraction(_ interaction: UIContextMenuInteraction, configurationForMenuAtLocation location: CGPoint) -> UIContextMenuConfiguration? {

        // 第一个菜单
        let favorite = UIAction(title: "Favorite", image: UIImage(systemName: "heart.fill")) { action in
            print("favorite")
        }

        // 第二个菜单
        let share = UIAction(title: "Share", image: UIImage(systemName: "square.and.arrow.up.fill")) { action in
            print("share")
        }

        // 第三个菜单
        let delete = UIAction(title: "Delete", image: UIImage(systemName: "trash.fill"), attributes: [.destructive]) { action in
            print("delete")
        }

        // 返回UIContextMenuConfiguration
        return UIContextMenuConfiguration(identifier: nil, previewProvider: nil) { _ in
            UIMenu(title: "Actions", children: [favorite, share, delete])
        }
    }
}

• 效果

UITableView和UICollectionView

iOS 13 以后，UITableView 和 UICollectionView 也支持 Context Menus，使用起来特别简单，只需要实现相应的代理方法，返回UIContextMenuConfiguration即可。

• UITableView

func tableView(_ tableView: UITableView, contextMenuConfigurationForRowAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {

    let favorite = UIAction(title: "Favorite", image: UIImage(systemName: "heart.fill")) { action in
        print("favorite")
    }

    let share = UIAction(title: "Share", image: UIImage(systemName: "square.and.arrow.up.fill")) { action in
        print("share")
    }

    let delete = UIAction(title: "Delete", image: UIImage(systemName: "trash.fill"), attributes: [.destructive]) { action in
        print("delete")
    }

    return UIContextMenuConfiguration(identifier: nil, previewProvider: nil) { _ in
        UIMenu(title: "Actions", children: [favorite, share, delete])
    }
}

• UICollectionView

func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? { 

    let favorite = UIAction(title: "Favorite", image: UIImage(systemName: "heart.fill")) { action in
        print("favorite")
    }

    let share = UIAction(title: "Share", image: UIImage(systemName: "square.and.arrow.up.fill")) { action in
        print("share")
    }

    let delete = UIAction(title: "Delete", image: UIImage(systemName: "trash.fill"), attributes: [.destructive]) { action in
        print("delete")
    }

    return UIContextMenuConfiguration(identifier: nil, previewProvider: nil) { _ in
        UIMenu(title: "Actions", children: [favorite, share, delete])
    }
}