iOS：目前是否有辦法阻止兩個視圖控制器同時被推入或彈出？

Question

我看到的唯一解決方案是對一個計算器問題的回答。我發佈了下面的鏈接。我指的是第五個答案。似乎有些用戶在解決方案方面存在一些問題。我不知道是否有另一個類別可以阻止兩個控制器同時被推送。任何提示或建議表示讚賞。

#import "UINavigationController+Consistent.h" 
#import <objc/runtime.h> 
/// This char is used to add storage for the isPushingViewController property. 
static char const * const ObjectTagKey = "ObjectTag"; 

@interface UINavigationController() 
@property (readwrite,getter = isViewTransitionInProgress) BOOL viewTransitionInProgress; 

@end 

@implementation UINavigationController (Consistent) 

- (void)setViewTransitionInProgress:(BOOL)property { 
NSNumber *number = [NSNumber numberWithBool:property]; 
objc_setAssociatedObject(self, ObjectTagKey, number , OBJC_ASSOCIATION_RETAIN); 
} 


- (BOOL)isViewTransitionInProgress { 
NSNumber *number = objc_getAssociatedObject(self, ObjectTagKey); 

return [number boolValue]; 
} 


#pragma mark - Intercept Pop, Push, PopToRootVC 
/// @name Intercept Pop, Push, PopToRootVC 

- (NSArray *)safePopToRootViewControllerAnimated:(BOOL)animated { 
if (self.viewTransitionInProgress) return nil; 
if (animated) { 
    self.viewTransitionInProgress = YES; 
} 
//-- This is not a recursion, due to method swizzling the call below calls the original method. 
return [self safePopToRootViewControllerAnimated:animated]; 

} 


    - (NSArray *)safePopToViewController:(UIViewController *)viewController animated:(BOOL)animated { 
if (self.viewTransitionInProgress) return nil; 
if (animated) { 
    self.viewTransitionInProgress = YES; 
    } 
//-- This is not a recursion, due to method swizzling the call below calls the original method. 
return [self safePopToViewController:viewController animated:animated]; 
    } 


- (UIViewController *)safePopViewControllerAnimated:(BOOL)animated { 
if (self.viewTransitionInProgress) return nil; 
if (animated) { 
    self.viewTransitionInProgress = YES; 
} 
//-- This is not a recursion, due to method swizzling the call below calls the original method. 
return [self safePopViewControllerAnimated:animated]; 
} 



    - (void)safePushViewController:(UIViewController *)viewController animated:(BOOL)animated { 
self.delegate = self; 
//-- If we are already pushing a view controller, we dont push another one. 
if (self.isViewTransitionInProgress == NO) { 
    //-- This is not a recursion, due to method swizzling the call below calls the original method. 
    [self safePushViewController:viewController animated:animated]; 
    if (animated) { 
     self.viewTransitionInProgress = YES; 
    } 
    } 
    } 


// This is confirmed to be App Store safe. 
// If you feel uncomfortable to use Private API, you could also use the delegate method navigationController:didShowViewController:animated:. 
- (void)safeDidShowViewController:(UIViewController *)viewController animated:(BOOL)animated { 
//-- This is not a recursion. Due to method swizzling this is calling the original method. 
[self safeDidShowViewController:viewController animated:animated]; 
self.viewTransitionInProgress = NO; 
} 


// If the user doesnt complete the swipe-to-go-back gesture, we need to intercept it and set the flag to NO again. 
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated { 
id<UIViewControllerTransitionCoordinator> tc = navigationController.topViewController.transitionCoordinator; 
[tc notifyWhenInteractionEndsUsingBlock:^(id<UIViewControllerTransitionCoordinatorContext> context) { 
    self.viewTransitionInProgress = NO; 
    //--Reenable swipe back gesture. 
    self.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)viewController; 
    [self.interactivePopGestureRecognizer setEnabled:YES]; 
}]; 
//-- Method swizzling wont work in the case of a delegate so: 
//-- forward this method to the original delegate if there is one different than ourselves. 
if (navigationController.delegate != self) { 
    [navigationController.delegate navigationController:navigationController 
           willShowViewController:viewController 
               animated:animated]; 
} 
} 


    + (void)load { 
//-- Exchange the original implementation with our custom one. 
method_exchangeImplementations(class_getInstanceMethod(self, @selector(pushViewController:animated:)), class_getInstanceMethod(self, @selector(safePushViewController:animated:))); 
method_exchangeImplementations(class_getInstanceMethod(self, @selector(didShowViewController:animated:)), class_getInstanceMethod(self, @selector(safeDidShowViewController:animated:))); 
method_exchangeImplementations(class_getInstanceMethod(self, @selector(popViewControllerAnimated:)), class_getInstanceMethod(self, @selector(safePopViewControllerAnimated:))); 
method_exchangeImplementations(class_getInstanceMethod(self, @selector(popToRootViewControllerAnimated:)), class_getInstanceMethod(self, @selector(safePopToRootViewControllerAnimated:))); 
method_exchangeImplementations(class_getInstanceMethod(self, @selector(popToViewController:animated:)), class_getInstanceMethod(self, @selector(safePopToViewController:animated:))); 
} 

@end 

iOS app error - Can't add self as subview

Answer 1

更新答案：

我喜歡這個解決方案由nonamelive在Github上什麼，我原貼：https://gist.github.com/nonamelive/9334458。通過繼承UINavigationController並利用UINavigationControllerDelegate，您可以確定發生轉換的時間，防止在轉換期間發生其他轉換，並且在同一個類中進行轉換。下面是其中不包括私有API nonamelive的解決方案的更新：

#import "NavController.h" 

@interface NavController() 

@property (nonatomic, assign) BOOL shouldIgnorePushingViewControllers; 

@end 

@implementation NavController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 
} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated 
{ 
    if (!self.shouldIgnorePushingViewControllers) 
    { 
     [super pushViewController:viewController animated:animated]; 
    } 
    self.shouldIgnorePushingViewControllers = YES; 
} 

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated { 
    self.shouldIgnorePushingViewControllers = NO; 
} 

@end 

---

以前的答案：

問題與此以前的答案：isBeingPresented和isBeingDismissed只有在viewDidLoad:或viewDidApper:

工作

儘管我避風港我自己沒有測試過，這裏有一個建議。

由於您使用的是UINavigationController，您可以訪問您的導航堆棧的內容，就像這樣：

NSArray *viewControllers = self.navigationController.viewControllers; 

並通過視圖控制器的數組，你可以訪問，如果需要的部分或全部相關指數是。

幸運的是，在iOS 5中引入了兩個特別方便的方法：和isBeingDismissed，如果視圖控制器分別處於呈現或被解散的過程中，則返回「YES」否則爲「否」。

因此，舉例來說，這裏有一個方法：

NSArray *viewControllers = self.navigationController.viewControllers; 

for (UIViewController *viewController in viewControllers) { 

    if (viewController.isBeingPresented || viewController.isBeingDismissed) { 
     // In this case when a pop or push is already in progress, don't perform 
     // a pop or push on the current view controller. Perhaps return to this 
     // method after a delay to check this conditional again. 
     return; 
    } 
} 

// Else if you make it through the loop uninterrupted, perform push or pop 
// of the current view controller. 

實際上，你可能不會通過堆棧上的每個視圖控制器有循環，但也許這個建議將幫助你動身的右腳。

Answer 2

這裏是我的方法，使用UINavigationController類別和方法swizzling。 方法-[UINavigationController didShowViewController:animated:]是私人的，所以雖然已經報告使用安全，但使用您自己的風險。

對於想法和NSHipster積分轉到this answer爲方法swizzling代碼。 This answer也有一個有趣的方法。

// 
// UINavigationController+Additions.h 
// 

@interface UINavigationController (Additions) 

@property (nonatomic, getter = isViewTransitionInProgress) BOOL viewTransitionInProgress; 

@end 


// 
// UINavigationController+Additions.m 
// 

#import "UINavigationController+Additions.h" 
#import <objc/runtime.h> 

static void *UINavigationControllerViewTransitionInProgressKey = &UINavigationControllerViewTransitionInProgressKey; 

@interface UINavigationController() 
// Private method, use at your own risk. 
- (void)didShowViewController:(UIViewController *)viewController animated:(BOOL)animated; 
@end 


@implementation UINavigationController (Additions) 

+ (void)load 
{ 
    static dispatch_once_t onceToken; 
    dispatch_once(&onceToken, ^{ 
     Class class = [self class]; 

     SEL originalSelector1 = @selector(pushViewController:animated:); 
     SEL swizzledSelector1 = @selector(zwizzledForViewTransitionInProgress_pushViewController:animated:); 

     Method originalMethod1 = class_getInstanceMethod(class, originalSelector1); 
     Method swizzledMethod1 = class_getInstanceMethod(class, swizzledSelector1); 

     BOOL didAddMethod1 = class_addMethod(class, originalSelector1, method_getImplementation(swizzledMethod1), method_getTypeEncoding(swizzledMethod1)); 

     if (didAddMethod1) { 
      class_replaceMethod(class, swizzledSelector1, method_getImplementation(originalMethod1), method_getTypeEncoding(originalMethod1)); 
     } else { 
      method_exchangeImplementations(originalMethod1, swizzledMethod1); 
     } 

     SEL originalSelector2 = @selector(didShowViewController:animated:); 
     SEL swizzledSelector2 = @selector(zwizzledForViewTransitionInProgress_didShowViewController:animated:); 

     Method originalMethod2 = class_getInstanceMethod(class, originalSelector2); 
     Method swizzledMethod2 = class_getInstanceMethod(class, swizzledSelector2); 

     BOOL didAddMethod2 = class_addMethod(class, originalSelector2, method_getImplementation(swizzledMethod2), method_getTypeEncoding(swizzledMethod2)); 

     if (didAddMethod2) { 
      class_replaceMethod(class, swizzledSelector2, method_getImplementation(originalMethod2), method_getTypeEncoding(originalMethod2)); 
     } else { 
      method_exchangeImplementations(originalMethod2, swizzledMethod2); 
     } 

    }); 
} 

- (void)zwizzledForViewTransitionInProgress_pushViewController:(UIViewController *)viewController animated:(BOOL)animated 
{ 
    if (self.viewTransitionInProgress) { 
     LogWarning(@"Pushing a view controller while an other view transition is in progress. Aborting."); 
    } else { 
     self.viewTransitionInProgress = YES; 
     [self zwizzledForViewTransitionInProgress_pushViewController:viewController animated:animated]; 
    } 
} 

- (void)zwizzledForViewTransitionInProgress_didShowViewController:(UIViewController *)viewController animated:(BOOL)animated 
{ 
    [self zwizzledForViewTransitionInProgress_didShowViewController:viewController animated:YES]; 
    self.viewTransitionInProgress = NO; 
} 

- (void)setViewTransitionInProgress:(BOOL)viewTransitionInProgress 
{ 
    NSNumber *boolValue = [NSNumber numberWithBool:viewTransitionInProgress]; 
    objc_setAssociatedObject(self, UINavigationControllerViewTransitionInProgressKey, boolValue, OBJC_ASSOCIATION_RETAIN); 
} 

- (BOOL)isViewTransitionInProgress 
{ 
    NSNumber *viewTransitionInProgress = objc_getAssociatedObject(self, UINavigationControllerViewTransitionInProgressKey); 
    return [viewTransitionInProgress boolValue]; 
} 

@end 

Answer 3

受@Lindsey Scott啓發回答我創建了UINavigationController子類。我的解決方案的優點是它也可以處理彈出，並且您可以在沒有任何問題的情況下實際執行所有請求（這是通過acceptConflictingCommands標誌進行控制的）。

MyNavigationController.h

#import <UIKit/UIKit.h> 

@interface MyNavigationController : UINavigationController 

@property(nonatomic, assign) BOOL acceptConflictingCommands; 

@end 

MyNavigationController.m

#import "MyNavigationController.h" 

@interface MyNavigationController()<UINavigationControllerDelegate> 

@property(nonatomic, assign) BOOL shouldIgnoreStackRequests; 
@property(nonatomic, strong) NSMutableArray* waitingCommands; 

@end 

@implementation MyNavigationController 

-(instancetype)init 
{ 
    if(self = [super init]) 
    { 
     self.delegate = self; 
     _waitingCommands = [NSMutableArray new]; 
    } 

    return self; 
} 

-(instancetype)initWithRootViewController:(UIViewController *)rootViewController 
{ 
    if(self = [super initWithRootViewController:rootViewController]) 
    { 
     self.delegate = self; 
     _waitingCommands = [NSMutableArray new]; 
     _acceptConflictingCommands = YES; 
    } 

    return self; 
} 

-(void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated 
{ 
    if(!_shouldIgnoreStackRequests) 
    { 
     [super pushViewController:viewController animated:animated]; 

     _shouldIgnoreStackRequests = YES; 
    } 
    else if (_acceptConflictingCommands) 
    { 
     __weak typeof(self) weakSelf = self; 

     //store and push it after current transition ends 
     [_waitingCommands addObject:^{ 

      id strongSelf = weakSelf; 

      [strongSelf pushViewController:viewController animated:animated]; 

     }]; 
    } 

} 

-(UIViewController *)popViewControllerAnimated:(BOOL)animated 
{ 
    __block UIViewController* popedController = nil; 

    if(1 < self.viewControllers.count) 
    { 
     if(!_shouldIgnoreStackRequests) 
     { 
      popedController = [super popViewControllerAnimated:animated]; 

      _shouldIgnoreStackRequests = YES; 
     } 
     else if(_acceptConflictingCommands) 
     { 
      __weak typeof(self) weakSelf = self; 

      [_waitingCommands addObject:^{ 

       id strongSelf = weakSelf; 

       popedController = [strongSelf popViewControllerAnimated:animated]; 

      }]; 
     } 
    } 

    return popedController; 
} 

#pragma mark - uinavigationcontroller delegate 
- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated 
{ 
    _shouldIgnoreStackRequests = NO; 

    if(0 < _waitingCommands.count) 
    { 
     void(^waitingAction)() = _waitingCommands.lastObject; 
     [_waitingCommands removeLastObject]; 
     waitingAction(); 
    } 
} 

@end 

當然，你可以改變acceptConflictingCommands的默認值，或從外部控制它。

如果您的代碼恰好使用popToRootViewController，setViewControllers：animated：和/或popToViewController，您必須以相同方式覆蓋它們以確保它們不會制動導航堆棧。