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
Swift 5 __ Xcode 11.5
在我的情况下,我想做一个动画,当它完成后,返回。 一种覆盖后退按钮默认动作的方法 调用你的自定义动作是这样的:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
setBtnBack()
}
private func setBtnBack() {
for vw in navigationController?.navigationBar.subviews ?? [] where "\(vw.classForCoder)" == "_UINavigationBarContentView" {
print("\(vw.classForCoder)")
for subVw in vw.subviews where "\(subVw.classForCoder)" == "_UIButtonBarButton" {
let ctrl = subVw as! UIControl
ctrl.removeTarget(ctrl.allTargets.first, action: nil, for: .allEvents)
ctrl.addTarget(self, action: #selector(backBarBtnAction), for: .touchUpInside)
}
}
}
@objc func backBarBtnAction() {
doSomethingBeforeBack { [weak self](isEndedOk) in
if isEndedOk {
self?.navigationController?.popViewController(animated: true)
}
}
}
private func doSomethingBeforeBack(completion: @escaping (_ isEndedOk:Bool)->Void ) {
UIView.animate(withDuration: 0.25, animations: { [weak self] in
self?.vwTxt.alpha = 0
}) { (isEnded) in
completion(isEnded)
}
}
或者你可以使用这个方法一次来探索NavigationBar视图层次结构,并获得访问_UIButtonBarButton视图的索引,转换为UIControl,删除目标-动作,并添加你的自定义目标-动作:
private func debug_printSubviews(arrSubviews:[UIView]?, level:Int) {
for (i,subVw) in (arrSubviews ?? []).enumerated() {
var str = ""
for _ in 0...level {
str += "\t"
}
str += String(format: "%2d %@",i, "\(subVw.classForCoder)")
print(str)
debug_printSubviews(arrSubviews: subVw.subviews, level: level + 1)
}
}
// Set directly the indexs
private func setBtnBack_method2() {
// Remove or comment the print lines
debug_printSubviews(arrSubviews: navigationController?.navigationBar.subviews, level: 0)
let ctrl = navigationController?.navigationBar.subviews[1].subviews[0] as! UIControl
print("ctrl.allTargets: \(ctrl.allTargets)")
ctrl.removeTarget(ctrl.allTargets.first, action: nil, for: .allEvents)
print("ctrl.allTargets: \(ctrl.allTargets)")
ctrl.addTarget(self, action: #selector(backBarBtnAction), for: .touchUpInside)
print("ctrl.allTargets: \(ctrl.allTargets)")
}
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
}
如果你正在使用navigationController,那么将UINavigationControllerDelegate协议添加到类中,并添加delegate方法,如下所示:
class ViewController:UINavigationControllerDelegate {
func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController,
animated: Bool) {
if viewController === self {
// do here what you want
}
}
}
每当导航控制器滑到新屏幕时,就调用此方法。如果返回按钮被按下,新的视图控制器就是ViewController本身。
你可以在视图控制器中做一些事情
override func navigationShouldPopOnBackButton() -> Bool {
self.backAction() //Your action you want to perform.
return true
}
完整回答使用 当导航条上的“后退”按钮被按下时进行检测
斯威夫特4.2:
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if self.isMovingFromParent {
// Your code...
}
}