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
只需control +拖动栏项到func下面。魅力工作
@IBAction func done(sender: AnyObject) {
if((self.presentingViewController) != nil){
self.dismiss(animated: false, completion: nil)
print("done")
}
}
其他回答
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if self.isMovingToParent {
//your code backView
}
}
只需control +拖动栏项到func下面。魅力工作
@IBAction func done(sender: AnyObject) {
if((self.presentingViewController) != nil){
self.dismiss(animated: false, completion: nil)
print("done")
}
}
我通过调用/重写viewWillDisappear来实现这一点,然后像这样访问navigationController的堆栈:
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(animated)
let stack = self.navigationController?.viewControllers.count
if stack >= 2 {
// for whatever reason, the last item on the stack is the TaskBuilderViewController (not self), so we only use -1 to access it
if let lastitem = self.navigationController?.viewControllers[stack! - 1] as? theViewControllerYoureTryingToAccess {
// hand over the data via public property or call a public method of theViewControllerYoureTryingToAccess, like
lastitem.emptyArray()
lastitem.value = 5
}
}
}
我的偏好是在导航控制器中覆盖popViewController。这样做的好处是:
你的应用程序保持默认的后退按钮外观和动画,你不需要管理它。如果用户在手机上设置了大号文本,这尤其有用,因为默认的后退按钮会根据用户的设置增加或减少大小。 你可以完全停止视图弹出,不像使用viewWillDisappear。
首先,创建一个自定义导航控制器类(并确保将其分配给故事板中的导航控制器或任何创建导航控制器的地方):
class NavControllerWithBackButtonOverride: UINavigationController {
var backButtonOverride: (() -> Void)? = nil
override func popViewController(animated: Bool) -> UIViewController? {
if backButtonOverride != nil {
//if anything is assigned to the backButtonOverride the override will run
self.backButtonOverride!()
return nil
} else {
//otherwise the default popViewController will run
return super.popViewController(animated: animated)
}
}
}
然后通过给backButtonOverride变量赋值,在视图控制器中启用/禁用重载:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.enableCustomBackButton()
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
self.disableCustomBackButton()
}
/**
Custom Back Button
*/
func customBackButtonAction() {
print("DO THIS INSTEAD")
}
func enableCustomBackButton() {
if let nav = self.navigationController as? NavControllerWithBackButtonOverride {
nav.backButtonOverride = { self.customBackButtonAction() }
nav.interactivePopGestureRecognizer?.isEnabled = false
}
}
func disableCustomBackButton() {
if let nav = self.navigationController as? NavControllerWithBackButtonOverride {
nav.backButtonOverride = nil
nav.interactivePopGestureRecognizer?.isEnabled = true
}
}
注意:我还禁用了interactivePopGestureRecognizer,因为它会导致自定义设置的问题。
这并不像我们想象的那么难。只需要为UIButton创建一个背景颜色清晰的框架,为按钮分配动作,并放置在导航栏后退按钮上。最后在使用后取下按钮。
这是Swift 3 用UIImage代替UIButton的示例代码
override func viewDidLoad() {
super.viewDidLoad()
let imageView = UIImageView()
imageView.backgroundColor = UIColor.clear
imageView.frame = CGRect(x:0,y:0,width:2*(self.navigationController?.navigationBar.bounds.height)!,height:(self.navigationController?.navigationBar.bounds.height)!)
let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(back(sender:)))
imageView.isUserInteractionEnabled = true
imageView.addGestureRecognizer(tapGestureRecognizer)
imageView.tag = 1
self.navigationController?.navigationBar.addSubview(imageView)
}
编写需要执行的代码
func back(sender: UIBarButtonItem) {
// Perform your custom actions}
_ = self.navigationController?.popViewController(animated: true)
}
执行操作后删除子视图
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
for view in (self.navigationController?.navigationBar.subviews)!{
if view.tag == 1 {
view.removeFromSuperview()
}
}