从弹出的UINavigationController或UITabBarController确定viewWillAppear [英] Determine viewWillAppear from Popped UINavigationController or UITabBarController

问题描述

我无法找到一种方法来区分是从Nav控制器堆栈弹出还是从UITabBarController进入视图控制器.

I am unable to find a way to distinguish between popping from the Nav controller stack and entering the view controller from the UITabBarController.

我只想在从TabBar呈现视图时才调用ViewWillAppear中的方法，而不是在有人向后按导航控制器时调用它.

I want to call a method in ViewWillAppear only when the view is presented from the TabBar, not when someone presses back in the navigation controller.

如果我不使用TabBarController，则可以使用viewDidLoad轻松获得此功能.

If I wasn't using a TabBarController, I could easily get this functionally using viewDidLoad.

我尝试过

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)

    println("View Will Appear")

    if isBeingPresented() {
        println("BP")
    }
    if isMovingFromParentViewController() {
        println("from")
    }
    if isMovingToParentViewController() {
        println("to")
    }
}

但是当我出现时，与按Tab键或按向后按钮没有区别.

But there is no difference when I present from pressing the Tab Button or when press back button.

只有视图将出现"被调用.

Only the "View Will Appear" is getting called.

使用iOS 8.4/Swift

Using iOS 8.4 / Swift

推荐答案

听起来很像

Sounds like a good use of the UITabBarControllerDelegate.

首先，在ViewController comingFromTab上添加Bool属性:

First, add a Bool property on your ViewController comingFromTab:

class MyViewController: UIViewController {
    var comingFromTab = false

    // ...
}

将UITabBarControllerDelegate设置为所需的任何类，并实现方法shouldSelectViewController.您可能还想继承UITabBarController的子类，然后将它们放在其中.

Set your UITabBarControllerDelegate to whatever class you want and implement the method shouldSelectViewController. You may also want to subclass UITabBarController and put them in there.

func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {

    if let myViewController = viewController as? MyViewController {
        myViewController.comingFromTab = true
}

如果标签的初始视图控制器是UINavigationController，则必须将其解开并访问它的第一个视图控制器:

If your tab's initial view controller is a UINavigationController, you will have to unwrap that and access it's first view controller:

if let navController = viewController as? UINavigationController {
    if let myViewController = navController.viewControllers[0] as? MyViewController {
        // do stuff
    }
}

最后，在视图控制器的viewWillAppear中添加所需的任何功能:

Lastly, add whatever functionality you need in viewWillAppear in your view controller:

override func viewDidAppear(animated: Bool) {
    super.viewWillAppear(animated)

    // ...
    if comingFromTab {
        // Do whatever you need to do here if coming from the tab selection
        comingFromTab = false
    }
}

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