这是@oneway的 Swift 3 版本的答案，用于在导航栏后退按钮事件被触发之前捕获它。由于UINavigationBarDelegate不能用于UIViewController，您需要创建一个在navigationBar shouldPop被调用时触发的委托。
@objc public protocol BackButtonDelegate {
@objc optional func navigationShouldPopOnBackButton() -> Bool
}
extension UINavigationController: UINavigationBarDelegate {
public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
if viewControllers.count < (navigationBar.items?.count)! {
return true
}
var shouldPop = true
let vc = self.topViewController
if vc.responds(to: #selector(vc.navigationShouldPopOnBackButton)) {
shouldPop = vc.navigationShouldPopOnBackButton()
}
if shouldPop {
DispatchQueue.main.async {
self.popViewController(animated: true)
}
} else {
for subView in navigationBar.subviews {
if(0 < subView.alpha && subView.alpha < 1) {
UIView.animate(withDuration: 0.25, animations: {
subView.alpha = 1
})
}
}
}
return false
}
}
然后，在您的视图控制器中添加委托功能：
class BaseVC: UIViewController, BackButtonDelegate {
func navigationShouldPopOnBackButton() -> Bool {
if ... {
return true
} else {
return false
}
}
}
我意识到我们经常想为用户添加一个警报控制器来决定他们是否想要返回。return false如果是这样，您可以通过执行以下操作始终navigationShouldPopOnBackButton()运行并关闭视图控制器：
func navigationShouldPopOnBackButton() -> Bool {
let alert = UIAlertController(title: "Warning",
message: "Do you want to quit?",
preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Yes", style: .default, handler: { UIAlertAction in self.yes()}))
alert.addAction(UIAlertAction(title: "No", style: .cancel, handler: { UIAlertAction in self.no()}))
present(alert, animated: true, completion: nil)
return false
}
func yes() {
print("yes")
DispatchQueue.main.async {
_ = self.navigationController?.popViewController(animated: true)
}
}
func no() {
print("no")
}
