Navigate to a specific UIViewController after rece

问题:

I am developing an iOS application that handles a hierarchy of UIViewController objects using a UINavigationController:

MenuViewController
  |
  |-ListOfAnimalsViewController
    |
    |-AnimalDetailsViewController
  |
  |-ListOfPlantsViewController
    |
    |-PlantDetailsViewController

The application receives local NSNotification objects with information of a certain animal or plant. The usual behavior when you touch the notification is to open the application and load the first view controller in hierarchy.

Is there a way of programmatically navigating to an instance of a UIViewController deep in the hierarchy instead?

EDIT: I am not asking for pushing the controller into the navigation stack, but for pushing the previous controllers as well, i.e. I would like to keep the navigation schema above.

回答1:

I'm gonna have to disagree with Suresh. While this solution may work in a simple case like this where you only have 1 previous ViewController, what if you wanted to add a 10th ViewController and keep the entire hierarchy? First of all you'd have to pass the final piece of data you want to show (in this case the plant or animal) through every ViewController and you'd be creating 10 ViewControllers at once. The transition between the current ViewController and the 10th would be far from seamless, performance would be terrible. Also no need to go and create your own navigation system, no need to make things more complicated than they are since this issue isn't too difficult.

Just push the ViewController you want to show, that way you'll only be creating 1 ViewController. In every ViewController that can be pushed as a result of a notification (and all the ones below that), override the behavior of the back button. Check in the viewControllers property of the navigationController if the ViewController before is is the one you expect, using NSStringFromClass. If not, create an NSMutableArray as a copy of the viewControllers, create the ViewController you do expect and insert it at the second to last spot in the array. Then replace the entire stack by calling the setViewControllers:animated: method on the navigationController with the mutable array, animated NO. Finally do the pop. Again you'll have created just 1 ViewController at a time, keeping your performance optimal.

Ican't post code right now since I'm on an iPad but if you need it, just ask and I'll add an example when i have a real keyboard.

回答2:

If you know the name of the class you can use the following code to navigate.

NSString *className = @"viewControllerName";

    UIViewController* myClass = (UIViewController*)[[NSClassFromString(className) alloc] init];
[self.navigationController pushViewController:myClass animated:YES];

回答3:

I think you will have to invent your own mechanism for following the navigation order since there's nothing in an iOS view controller's static definition that defines an ordering. (Segues seem to be as close as it gets and that's not very close.)

If I had to do this for a hierarchy of view controllers with some unknown depth, I'd consider creating a superclass that worked with a path, sort of like network routing. It would have a method such as displayNextControllerOnPath:(NSString *)path. A MenuViewController that was a RoutingController subclass would receive a path like @"ListOfAnimalsViewController.AnimalDetailsViewController", strip off the first path element, instantiate it (it being another RoutingController subclass), and send it @"AnimalDetailsViewController".

Other details would involve knowing when to stop and perhaps passing an object or dictionary as a payload for the last controller to use as content.

回答4:

I would reconstruct the stack in the following way:

MenuViewController *menuController = [[MenuViewController alloc] init];
ListOfAnimalsViewController *listController = [[ListOfAnimalsViewController alloc] init];
AnimalDetailsViewController *detailsController = [[AnimalDetailsViewController alloc] init];
UINavigationController *navigationController = [[UINavigationController alloc] init];
[navigationController setViewControllers:@[menuController, listController, detailsController]];
self.window.rootViewController = navigationController;

You may need to set some properties to based on your implementations.