blocks|key|1179145|text|我假设你的意思是，当你说推到堆栈上时，你的视图正在通过推送一个新的视图来向导航控制器的堆栈下移。我建议使用viewDidUnload方法添加一个NSLog语句，以便向控制台写入一些内容，这样您就可以看到发生了什么，您可能想要向viewWillDissappeer添加一个NSLog。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1179146|entityMap^0|1H|D|20|5|35|I|3R|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

I assume you mean that your view is being moved down the navigation controller's stack by the pushing a new view when you say pushed onto the stack. I would suggest using the <code>viewDidUnload</code> method to add a <code>NSLog</code> statement to write something to the console so you can see what is going on, you may want to add a <code>NSLog</code> to <code>viewWillDissappeer</code>.

blocks|key|1179165|text|您可以使用以下代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1179166|-+(void)viewWillDisappear:(BOOL)animated+{
++[super+viewWillDisappear:animated];
++NSArray+*viewControllers+=+self.navigationController.viewControllers;
++if+(viewControllers.count+>+1+&&+[viewControllers+objectAtIndex:viewControllers.count-2]+==+self)+{
++++//+View+is+disappearing+because+a+new+view+controller+was+pushed+onto+the+stack
++++NSLog(@"New+view+controller+was+pushed");
++}+else+if+([viewControllers+indexOfObject:self]+==+NSNotFound)+{
++++//+View+is+disappearing+because+it+was+popped+from+the+stack
++++NSLog(@"View+controller+was+popped");
++}
}|code-block|syntax|javascript|1179167|当然，这是可能的，因为在调用viewWillDisappear时，UINavigationController的视图控制器堆栈(通过viewControllers属性公开)已经更新。|1179168|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can use the following.

<pre><code>- (void)viewWillDisappear:(BOOL)animated {
 [super viewWillDisappear:animated];
 NSArray *viewControllers = self.navigationController.viewControllers;
 if (viewControllers.count &gt; 1 &amp;&amp; [viewControllers objectAtIndex:viewControllers.count-2] == self) {
 // View is disappearing because a new view controller was pushed onto the stack
 NSLog(@"New view controller was pushed");
 } else if ([viewControllers indexOfObject:self] == NSNotFound) {
 // View is disappearing because it was popped from the stack
 NSLog(@"View controller was popped");
 }
}
</code></pre>

This is, of course, possible because the UINavigationController's view controller stack (exposed through the viewControllers property) has been updated by the time that viewWillDisappear is called.

blocks|key|1179228|text|如果您只是想知道视图是否正在弹出，当从控制器堆栈中删除时，我刚刚发现self.navigationController在viewDidDisappear中是nil。所以这是一个简单的替代测试。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1179229|(这是我在尝试了各种其他扭曲方法后发现的。我很惊讶没有导航控制器协议来注册一个视图控制器来通知pops。您不能使用UINavigationControllerDelegate，因为它实际上做了实际的显示工作。)|1179230|entityMap^0|Y|P|1O|G|26|3|0|1L|U|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

If you just want to know whether your view is getting popped, I just discovered that <code>self.navigationController</code> is <code>nil</code> in <code>viewDidDisappear</code>, when it is removed from the stack of controllers. So that's a simple alternative test.

(This I discover after trying all sorts of other contortions. I'm surprised there's no navigation controller protocol to register a view controller to be notified on pops. You can't use <code>UINavigationControllerDelegate</code> because that actually does real display work.)

blocks|key|1179247|text|我认为最简单的方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1179248|+-+(void)viewWillDisappear:(BOOL)animated
{
++++if+([self+isMovingFromParentViewController])
++++{
++++++++NSLog(@"View+controller+was+popped");
++++}
++++else
++++{
++++++++NSLog(@"New+view+controller+was+pushed");
++++}
++++[super+viewWillDisappear:animated];
}|code-block|syntax|javascript|1179249|Swift：|1179250|override+func+viewWillDisappear(animated:+Bool)
{
++++if+isMovingFromParent
++++{
++++++++print("View+controller+was+popped")
++++}
++++else
++++{
++++++++print("New+view+controller+was+pushed")
++++}
++++super.viewWillDisappear(animated)
}|1179251|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I think the easiest way is:

<pre><code> - (void)viewWillDisappear:(BOOL)animated
{
 if ([self isMovingFromParentViewController])
 {
 NSLog(@"View controller was popped");
 }
 else
 {
 NSLog(@"New view controller was pushed");
 }
 [super viewWillDisappear:animated];
}
</code></pre>

Swift:

<pre><code>override func viewWillDisappear(animated: Bool)
{
 if isMovingFromParent
 {
 print("View controller was popped")
 }
 else
 {
 print("New view controller was pushed")
 }
 super.viewWillDisappear(animated)
}
</code></pre>

blocks|key|1179279|text|这个问题已经相当陈旧了，但我无意中看到了它，所以我想把最佳实践(afaik)贴出来。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1179280|你可以直接做|1179281|if([self.navigationController.viewControllers+indexOfObject:self]==NSNotFound)
+//+view+controller+popped
}|code-block|syntax|javascript|1179282|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

This question is fairly old but I saw it by accident so I want to post best practice (afaik)

you can just do

<pre><code>if([self.navigationController.viewControllers indexOfObject:self]==NSNotFound)
 // view controller popped
}
</code></pre>

blocks|key|1394840|text|在iOS+6%2B中，Segues是处理此问题的一种非常有效的方法。如果您在接口生成器中为特定段指定了标识符，则可以在prepareForSegue中检查它。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1394841|-+(void)prepareForSegue:(UIStoryboardSegue+*)segue+sender:(id)sender
{
++++if+([segue.identifier+isEqualToString:@"LoginSegue"])+{
+++++++NSLog(@"Push");
+++++++//+Do+something+specific+here,+or+set+a+BOOL+indicating
+++++++//+a+push+has+occurred+that+will+be+checked+later
++++}
}|code-block|syntax|javascript|1394842|entityMap^0|1L|F|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Segues can be a very effective way of handling this problem in iOS 6+. If you have given the particular segue an identifier in Interface Builder you can check for it in <code>prepareForSegue</code>.

<pre><code>- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
 if ([segue.identifier isEqualToString:@"LoginSegue"]) {
 NSLog(@"Push");
 // Do something specific here, or set a BOOL indicating
 // a push has occurred that will be checked later
 }
}
</code></pre>

blocks|key|1179366|text|在Swift中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1179367|+override+func+viewWillDisappear(animated:+Bool)+{
++++if+let+navigationController+=+self.navigationController+{
++++++++if+!contains(navigationController.viewControllers+as!+Array<UIViewController>,+self)+{
++++++++}
++++}

++++super.viewWillDisappear(animated)

}|code-block|syntax|javascript|1179368|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In Swift: 

<pre><code> override func viewWillDisappear(animated: Bool) {
 if let navigationController = self.navigationController {
 if !contains(navigationController.viewControllers as! Array&lt;UIViewController&gt;, self) {
 }
 }

 super.viewWillDisappear(animated)

}
</code></pre>

blocks|key|1179375|text|Swift+4|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1179376|override+func+viewWillDisappear(_+animated:+Bool)
++++{
++++++++if+self.isMovingFromParent
++++++++{
++++++++++++//View+Controller+Popped
++++++++}
++++++++else
++++++++{
++++++++++++//New+view+controller+pushed
++++++++}
+++++++super.viewWillDisappear(animated)
++++}|code-block|syntax|javascript|1179377|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Swift 4
<pre><code>override func viewWillDisappear(_ animated: Bool)
 {
 if self.isMovingFromParent
 {
 //View Controller Popped
 }
 else
 {
 //New view controller pushed
 }
 super.viewWillDisappear(animated)
 }
</code></pre>

blocks|key|1179403|text|我发现苹果在这方面的文档很难理解。此扩展有助于查看每个导航处的状态。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1179404|extension+UIViewController+{
++++public+func+printTransitionStates()+{
++++++++print("isBeingPresented=\(isBeingPresented)")
++++++++print("isBeingDismissed=\(isBeingDismissed)")
++++++++print("isMovingToParentViewController=\(isMovingToParentViewController)")
++++++++print("isMovingFromParentViewController=\(isMovingFromParentViewController)")
++++}
}|code-block|syntax|javascript|1179405|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I find Apple's documentation on this is hard to understand. This extension helps see the states at each navigation.

<pre><code>extension UIViewController {
 public func printTransitionStates() {
 print("isBeingPresented=\(isBeingPresented)")
 print("isBeingDismissed=\(isBeingDismissed)")
 print("isMovingToParentViewController=\(isMovingToParentViewController)")
 print("isMovingFromParentViewController=\(isMovingFromParentViewController)")
 }
}
</code></pre>

blocks|key|1394921|text|谢谢@Bryan+Henry，仍然在Swift+5工作|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1394922|++++override+func+viewWillDisappear(_+animated:+Bool)+{
++++++++super.viewWillDisappear(animated)
++++++++if+let+controllers+=+navigationController?.children{
++++++++++++if+controllers.count+>+1,+controllers[controllers.count+-+2]+==+self{
++++++++++++++++//+View+is+disappearing+because+a+new+view+controller+was+pushed+onto+the+stack
++++++++++++++++print("New+view+controller+was+pushed")
++++++++++++}
++++++++++++else+if+controllers.firstIndex(of:+self)+==+nil{
++++++++++++++++//+View+is+disappearing+because+it+was+popped+from+the+stack
++++++++++++++++print("View+controller+was+popped")
++++++++++++}
++++++++}

++++}|code-block|syntax|javascript|1394923|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Thanks @Bryan Henry, Still works in Swift 5

<pre><code> override func viewWillDisappear(_ animated: Bool) {
 super.viewWillDisappear(animated)
 if let controllers = navigationController?.children{
 if controllers.count &gt; 1, controllers[controllers.count - 2] == self{
 // View is disappearing because a new view controller was pushed onto the stack
 print("New view controller was pushed")
 }
 else if controllers.firstIndex(of: self) == nil{
 // View is disappearing because it was popped from the stack
 print("View controller was popped")
 }
 }

 }
</code></pre>

I'm struggling to find a good solution to this problem. In a view controller's <code>-viewWillDisappear:</code> method, I need to find a way to determine whether it is because a view controller is being pushed onto the navigation controller's stack, or whether it is because the view controller is disappearing because it has been popped.

At the moment I'm setting flags such as <code>isShowingChildViewController</code> but it's getting fairly complicated. The only way I think I can detect it is in the <code>-dealloc</code> method.

viewWillDisappear: Determine whether view controller is being popped or is showing a sub-view controller

Swift

我正在努力为这个问题找到一个好的解决方案。在视图控制器的-viewWillDisappear:方法中，我需要找到一种方法来确定是因为视图控制器被推到了导航控制器的堆栈上，还是因为视图控制器因为被弹出而消失了。目前，我正在设置诸如isShowingChildViewController之类的标志，但它正变得相当复杂。我认...

问viewWillDisappear:确定视图控制器是否正在弹出或正在显示子视图控制器
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