UINavigationController 返回手勢與 leftBarButtonItem

UINavigationController 自帶從屏幕左側邊緣向右滑動的返回手勢，可以通過這個手勢實現 pop，或者 pop 中途取消 pop 而停留在當前控制器(UIViewController)。如果設置了當前控制器的 navigationItem.leftBarButtonItem 或 navigationItem.leftBarButtonItems，則返回手勢失效。可以通過自定義 NavigationController，實現設置 navigationItem.leftBarButtonItem 或 navigationItem.leftBarButtonItems，並且保留返回手勢。代碼已上傳 GitHub：https://github.com/Silence-GitHub/NavigationControllerDemo

UINavigationController 的 interactivePopGestureRecognizer 屬性為返回手勢。設置手勢的 delegate，手動管理返回手勢。當 UINavigationController 沒有或只有一個子控制器時，返回手勢不能響應，否則會出現奇怪的現象。自定義 currentNotRootVC 屬性，記錄當前的非根子控制器(只有一個子控制器時，此子控制器為根子控制器，root view controller)。設置 UINavigationController 的 delegate，通過 UINavigationControllerDelegate 的方法，更新 currentNotRootVC。代碼示例如下

import UIKit

class NavigationController: UINavigationController, UINavigationControllerDelegate, UIGestureRecognizerDelegate {

    // Current child view controller, but not root view controller
    private var currentNotRootVC: UIViewController?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        delegate = self
        interactivePopGestureRecognizer?.delegate = self
    }
    
    // MARK: - UINavigationControllerDelegate
    
    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        currentNotRootVC = viewControllers.count <= 1 ? nil : viewController
        /*
        switch viewController {
        case is SomeVCClassForbidPopGesture:
            interactivePopGestureRecognizer?.isEnabled = false
        default:
            interactivePopGestureRecognizer?.isEnabled = true
        }
         */
    }
    
    // MARK: - UIGestureRecognizerDelegate
    
    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        if interactivePopGestureRecognizer == gestureRecognizer {
            // Begin to pop only when top view controller is current child view controller but not root view controller
            return currentNotRootVC == topViewController
        }
        return true
    }

}

如果有部分控制器不允許返回手勢(例如編輯信息，退出頁面需要確認)，則在func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool)方法中，加入對 viewController 的判斷，開啟或禁用返回手勢。

參考：http://www.cnblogs.com/v2m_/p/3521569.html

轉載請註明出處：http://www.cnblogs.com/silence-cnblogs/p/6618056.html