呈现模式视图控制器时的异常：NSInternalInconsistencyException

Question

当我尝试呈现模式视图控制器时，发生异常：

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', 
reason: 'Attempting to begin a modal transition from <UINavigationController: 0x1d906060>
to <UINavigationController: 0x1da7a6d0> while a transition is already in progress. Wait
for viewDidAppear/viewDidDisappear to know the current transition has completed'

现在，我读了类似的问题，他们只是稍微延迟地打开了模态视图，例如

[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(openModalController) userInfo:nil repeats:NO];

演示文稿如下所示：

- (void)openImage:(ImageModel *)imageModel{
FullscreenImageViewController_iPhone * controller = [[FullscreenImageViewController_iPhone alloc] init];
controller.imageModel = imageModel;
UINavigationController * navController = [[UINavigationController alloc] initWithRootViewController:controller];
UIViewController * visibleController = [[AppDelegate_iPhone app] visibleViewController];
[visibleController presentViewController:navController animated:YES completion:^{

}];
}

这不是真正的解决方案，对吗？ 如何检查我的应用中某处是否正在进行过渡，并在当前过渡完成后立即打开新的模式视图？

Answer 1

这对我有用。 如果使用UIViewController的isBeingPresented和isBeingDismissed方法测试演示或解雇是否正在进行，请稍等片刻，然后重试：

- (void) presentVC {    
    if (presentingVC.isBeingPresented || presentingVC.isBeingDismissed) {
         double delayInSeconds = 0.3;
         dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
         dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
               [self presentVC];
         });
    }
    else {
        [presentingVC presentViewController:presentedVC animated:NO completion:nil];
    }
}