我需要执行一个动作(清空一个数组),当UINavigationController的后退按钮被按下,而按钮仍然导致堆栈上的前一个ViewController出现。我如何使用swift来实现这一点?
当前回答
当返回按钮按下,忽略交互式弹出与屏幕边缘手势。
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if isMovingFromParent, transitionCoordinator?.isInteractive == false {
// code here
}
}
其他回答
在我的例子中,viewWillDisappear效果最好。但在某些情况下,必须修改之前的视图控制器。所以这是我的解决方案访问之前的视图控制器,它在Swift 4中工作:
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if isMovingFromParentViewController {
if let viewControllers = self.navigationController?.viewControllers {
if (viewControllers.count >= 1) {
let previousViewController = viewControllers[viewControllers.count-1] as! NameOfDestinationViewController
// whatever you want to do
previousViewController.callOrModifySomething()
}
}
}
}
试试这个。
self.navigationItem.leftBarButtonItem?.target = "methodname"
func methodname ( ) {
// enter code here
}
这个也试试。
override func viewWillAppear(animated: Bool) {
//empty your array
}
这是我自己解决问题的方法
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.navigationItem.leftBarButtonItem?.action = #selector(self.back(sender:))
self.navigationItem.leftBarButtonItem?.target = self
}
@objc func back(sender: UIBarButtonItem) {
}
我通过以下方法做到了这一点:
斯威夫特3
override func didMoveToParentViewController(parent: UIViewController?) {
super.didMoveToParentViewController(parent)
if parent == nil {
println("Back Button pressed.")
delegate?.goingBack()
}
}
斯威夫特4
override func didMove(toParent parent: UIViewController?) {
super.didMove(toParent: parent)
if parent == nil {
debugPrint("Back Button pressed.")
}
}
不需要自定义后退按钮。
override func willMove(toParent parent: UIViewController?)
{
super.willMove(toParent: parent)
if parent == nil
{
print("This VC is 'will' be popped. i.e. the back button was pressed.")
}
}