嘗試在已經轉換時關閉演示控制器

Question

我使用iOS8 GM上的Xcode6 GM編譯我的項目。當解僱許多視圖控制器，我的應用程序總是崩潰和調試區域顯示：

"Trying to dismiss the presentation controller while transitioning already. transitionViewForCurrentTransition is not set, presentation controller was dismissed during the presentation? "

我用Google搜索，發現了類似的情況，並顯示了同樣的錯誤：

[self.viewController presentViewController:vc animated:NO completion:^{ 
     [self.viewController dismissViewControllerAnimated:NO completion:nil]; 
}]; 

它工作正常使用Xcode5和IOS 7 。錯誤的含義是什麼？ iOS8對「Hack」不滿意嗎？提前致謝。

Answer 1

我的解決辦法：

dismissViewControllerAnimated:completion:If you present several view controllers in succession, thus building a stack of presented view controllers, calling this method on a view controller lower in the stack dismisses its immediate child view controller and all view controllers above that child on the stack. When this happens, only the top-most view is dismissed in an animated fashion; any intermediate view controllers are simply removed from the stack.

例如，我有4個觀點：A-> B-> C-> D，當我想解僱B時，我首先檢查C是否也想通過使用objc_setAssociatedObject附加/分離NSString對象來解僱，如果C也想解僱，那麼只需取消C的請求。只需致電駁回B.

Answer 2

您是否試圖強制改變設備方向？ 總之，在我看來，你可以嘗試在當前的代碼更改爲：

[self.navigationController presentViewController:vc animated:NO completion:^{ 
    dispatch_after(0, dispatch_get_main_queue(), ^{ 
     [self.navigationController dismissViewControllerAnimated:NO completion:nil]; 
    }); 
}]; 

Answer 3

ThirdViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:@"Third"]; 
UIViewController *VC1 = self.presentingViewController; 
[self dismissViewControllerAnimated:NO completion:^{}]; 
[VC1 presentViewController:vc animated:YES completion:^{}]; 

Answer 4

我有同樣的問題，我發現一個乾淨的解決方案避免使用dispatch_async或dispatch_after。

簡單地說，正如異常所描述的那樣，當呈現轉換仍在進行中時，您試圖關閉視圖控制器。 這意味着，一旦

- presentViewController:animated:completion: 

完成塊被調用，調用該辭退的轉變尚未完成。

從iOS的7起過渡的UIViewController有一個可用的新方法

- transitionCoordinator 

的transitionCoordinator給你 機會盡快轉換完成後排隊完成塊。

該方法返回的對象符合UIViewControllerTransitionCoordinator協議。知道解決方案非常簡單。

的

- presentViewController:animated:completion: 

過渡協調器的調用之後被適當地由框架構成。

使用

- animateAlongsideTransition:completion: 

它發送正確完成塊。

這裏有點代碼段更好地解釋解決方案

void(^completion)() = ^() { 
    [modalViewController dismissViewControllerAnimated:YES completion:nil]; 
}; 

// This check is needed if you need to support iOS version older than 7.0 
BOOL canUseTransitionCoordinator = [viewController respondsToSelector:@selector(transitionCoordinator)]; 

if (animated && canUseTransitionCoordinator) 
{ 
    [viewController presentViewController:modalViewController animated:animated completion:nil]; 
    [viewController.transitionCoordinator animateAlongsideTransition:nil completion:^(id<UIViewControllerTransitionCoordinatorContext> context) { 
     completion(); 
    }]; 
} 
else 
{ 
    [viewController presentViewController:modalViewController animated:animated completion:completion]; 
}