当前可见视图控制器检查 [英] Current visible view controller checking

问题描述

我正在从我的AppDelegate类中检查我的ParentEndViewController当前是否是可见类.

I am checking from my AppDelegate class whether my ParentEndViewController is currently the visible class or not.

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone" bundle: nil];  
ParentEndViewController *parent = [storyboard instantiateViewControllerWithIdentifier:@"ParentEndViewController"];
 if (parent.isViewLoaded && parent.view.window){
         UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:displayName
                                                            message:body
                                                           delegate:nil
                                                  cancelButtonTitle:@"Ok"
                                                  otherButtonTitles:nil];
        [alertView show];
        NSLog(@"current view is parent!");
    }
    else{
        NSLog(@"current view is not parent!");
    }

它正在打印current view is not parent!".但是我确定在我的应用程序上运行的当前视图是ParentEndViewController，即它应该打印current view is parent!.

It is printing that current view is not parent!". But I am sure that the current view running on my app is ParentEndViewController, i.e it should print current view is parent!.

问题出在哪里?

推荐答案

问题是您在调用[storyboard instantiateViewControllerWithIdentifier:@"ParentEndViewController"];时实例化ParentEndViewController的新对象，此实例与根视图的实例不同控制器. 如果要在应用程序委托中检查应用程序的根视图控制器，则应尝试

The problem is that you instantiate a new object of ParentEndViewController when you call the [storyboard instantiateViewControllerWithIdentifier:@"ParentEndViewController"]; this instance is not the same as the instance of your root view controller. If you are checking the root view controller of your app in app delegate you should try

if([self.window.rootViewController isKindOfClass:[ParentEndViewController class]]) {
    NSLog(@"Luke I'm your father");
}
else {
    NSLog(@"Sorry bro, somebody else is the parent");
}

如果要检查导航控制器的最后一个视图控制器，则应尝试以下操作:

If you are checking the last view controller of your navigation controller you should try something like:

UIViewController *lastViewController = [[self.navigationController viewControllers] lastObject];

 if([lastViewController isKindOfClass:[ParentEndViewController class]) {
       NSLog(@"Luke I'm your father");
 }
 else {
     NSLog(@"Sorry bro, somebody else is the parent");
 }

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