I'm trying to get multiple levels of hierarchy working
with Navigation Controllers. I have 3 levels of hierarchy and
I can move down through the levels of hierarchy, but I can
only go back one level and not two levels, back to the starting
view.
I start by creating a navigation controller for View #1 and push the next
view, View #2, onto it. Then I add the navigation controller to the
subview of the window in didSelectRowAtIndexPath. Clicking on
a table row in View #1 , takes me to the next hiearchy level View #2.
This next hiearchy level view is also a table view. Here is where
I think the problem occurs. I create another navigation controller
and push View #3 onto it in didSelectRowAtIndexPath in the View
Controller for View #2. Clicking on a table row in View #2 takes
me to View #3. But when I use the back button to go back to View #2,
I go back to an empty view, and not the real View #2.
Do I only need one navigation controller to handle 3 levels of
hiearchy instead of two navigation controllers?
If #1 is yes, then how do I pass the navigation controller to view #2's
controller so that I can push View #3 onto the navigation controller?
Or do I need to push all three views onto the navigation controller
in View #1?
Or...?
Thanks in advance,
Jim
The UIViewController has been designed to work hand in hand with UINavigationController. When pushing a new view, a UINavigationController will inject references to itself and to a UINavigationItem containing metadata about the navigation (back button with the title of the view behind it etc...).
Generally, you want to initialize your UINavigationController with Interface Builder using the "NIB Name" field to specify the "root view controller" (i.e. the first view to appear which should not have a back button). The equivalent in code roughly looks like this:
UIViewController *rootController = [[UIViewController alloc] initWithNibName:#"RootController"];
UINavigationController *navCtl = [[UINavigationController alloc] initWithRootController:rootcontroller];
Then, when you need to push a new view controller (probably in your didSelectRowAtIndexPath delegate method in your rootController)
SecondViewController *secondViewController = [[SecondViewController alloc] initWithNibName:#"SecondViewController"];
[self.navigationController pushViewController:secondViewController];
[secondViewController release];
Notice that you didn't have to create the self.navigationController property, it is already defined in UIViewController and will be injected with the right reference depending on the current state of the navigation. It works like magic!
The DrillDownSave sample code from the Apple Developer site:
https://developer.apple.com/library/ios/#samplecode/DrillDownSave/
does exactly what I am looking for with three hierarchy levels of
views using the navigation controller. Thanks for your answers.
Jim
In general all of your hierarchy should be contained in a single UINavigationController. I am not sure if nesting them is even supported.
How would you do this IF the subsequent views are additional instances of the same controller, that is a true hierarchy of nothing more than table views... the example shows hard coded views... but they essentially do the same thing. My OO background says if I alloc/init a new instance of a controller, shouldn't I be able to push that, then have its state restored on pop (back button)? That doesn't seem to work for me. Each instance of the controller (UITableViewController) has its own instance of an array as its data...
Related
I got a tabbed application like this:
and already set up everything like it should look, but it won't function yet. I already googled my problem and they said you first need to set up a NavigationController with the table view as rootView and then the NavigationBar but I really couldn't figure it out. Hope someone of you can help me.
Based on your response to my comment on your question here is what you should be doing:
First off, in order to make it look like the settings app table, you will need to change the style of your UITableView to UITableViewStyleGrouped.
Your hierarchy will consist of the following:
The viewcontroller that is actually added into your UITabBarController viewControllers array(since I see you have a tabbar as your lowest level of navigation) should be an UINavigationController. The root viewcontroller of the navigation controller should be the uiviewcontroller subclass you made that contains your table view. (let's say it's called SettingsViewController)
SettingsViewController *settingsViewController = [[SettingsViewController alloc] init];
UINavigationController *settingsNavController = [[UINavigationController alloc] initWithRootViewController:settingsViewController];
You will probably need to create a different UIViewController subclass for each type of detail pane you're going to want (if they have different functionality).
In the didSelectRowAtIndexPath UITableViewDelegate function, you will create the appropriate detail viewcontroller and push it onto your navigation stack.
Let's say you have a volume settings view controller as an example. The following is the code you would have in the function I just mentioned. Keep in mind you also need to actually check the index and/or section of the selected row to figure out which detail view should be shown.
VolumeSettingsViewController *volumeSettings = [[VolumeSettingsViewController alloc] init];
[self.navigationController pushViewController:volumeSettings animated:YES];
By default, this will function pretty much like the Apple Settings app navigation. The navigation bar will automatically have a "back" button to take you back to the settings view.
If you are using a Storyboard, select your view controller, go to the "Edit" menu and choose, "Embed in Navigation Controller."
If not using story boards, assuming this will be done in code, you need to create things in a reverse order of their hierarchy - something like this:
Create an instance of the Einstellungen tab's TableViewController using initWithNibName:
Create a UINavigationController using initWithRootViewController: and setting the Einstellungen as the root
Create a UITabBarController and set your navigation controller as one of the view controllers of this tab bar controller
Add the tab bar controller as a subview to the main window in your application delegate
This will create this hierarchy:
Tab bar controller
->view controller: Navigation Controller -> root view controller: Einstellungen
I have a Navigation Controller with a root table view which has several links. Tapping each link moves to the next view (by pushing it to the navigation controller's stack). But suppose that in that "next view", I have a UIButton that should take me further to another view (by pushing on to the same navigation controller's stack)...
View Controller-->first view-->second view-->third view..........
Now, I can easily access the Navigation Controller when I deal with the first view (and successfully push it to the Navigation Controller's stack) because it has been instantiated in the same file itself. What my real doubt is--How do you access a Navigation Controller in a far off view controller (eg, the third view or fourth view etc)? Please note that I am not using any separate delegate. All the Navigation Bar methods have been implemented in one file and connected to the Navigation Controller via an outlet.
When you push a ViewController onto a NavigationController the ViewController will automatically have it's navigationController property set. This means you can access the same NAvigationController no matter where you are in the stack.
-Update-
navigationController
In every UIViewController you can access that property.
So to in any other UIViewController that has been pushed onto the stack you should be able to just do this:
[self.navigationController pushViewController:othercontroller animated:YES];
Look at the documentation for UIViewController to see what other magic properties you have available.
I have been stuck on this for a few days now and it is killing me... In my viewDidLoad event, I am trying to programmatically add a full screen UINavigationController to a subview of my view controller. So far, I have only succeeded in doing two things...
1) Only a grey screen shows up
OR
2) I get something that resembles a navigation controller added to the view controller, instead of being my navigation controller from a XIB it is just a generic one... even though I loaded from the XIB. Oddly enough it is always shifted 25 pixels downward and slightly cut off.
I have read every single link on google and I can't seem to figure this out. I just created a new viewcontroller... added a UINavigationController to it... try to load that view controller and it messes up.
Any help is greatly appreciated!!!!
Instead of having the UINavigationController be a child of some other view controller, make the UINavigationController the root controller itself. The navigation controller is one of the special "container" view controllers, and it generally wants to own the whole screen and be at the root of the controller hierarchy (except in certain circumstances).
Try something like this:
UINavigationController * rootNavController = [[UINavigationController alloc] initWithRootViewController:myRootControllerInTheNavController];
[window addSubview:[rootNavController view]];
Which will obscure any existing views with the nav controller (those existing things will still be there when you -removeFromSuperview the nav controller's view). The nuclear option is to set your UIWindow's rootViewController property with the nav controller, but it sounds from your comment that this may not be what you want to do here.
Possibly a cleaner approach: If it accomplishes what you want, I believe you could also take your nav controller and present it modally (see docs for uiviewcontroller) from whatever the current view controller is. Set the transition appropriately, and while you're in the nav stack, the nav controller will be visible.
I've been reading the Head First iPhone Development book and I understand how to get to a new view from a table but how exactly would I be able to get to a new view or view controller, by just simply pressing a button? Is that even possible?
I mean there are some apps where you click a button, not a table cell and it loads a new view. How exactly is that done? If someone could help out a newbie it would be greatly appreciated!
I think what you're looking for is a modal vew controller. THis presents a modal view like you described on top of everything else. If rootViewController is the view controller that is displaying your current view, and myNewViewController the view controller you want to display modally:
[rootViewController presentModalViewController:myNewViewController animated:YES];
There's plenty of examples of this kind of thing on the net, just search for presentModalViewController
Like bpapa said in the comments, it's hard to be specific without code. However, generally what you want to do is:
Build a navigation controller that contains one original view.
Create a button in your original view using the Interface Builder.
Build a callback method (usually defined with IBAction) that is run when the button is pushed.
In that callback method, create a new view and push it onto the navigation controller the same way you would using a table view cell.
Alternately, if you only want one level of hierarchy, you could use a modal view controller; instead of pushing onto the navigation controller in the last step, just present the modal view controller.
The general answer is that you have an object that manages which view controller loads when.
The most commonly used is the UINavigationController. It is a UIViewController that instead of controlling views, controls other view controllers. It works like a simple stack. You push views you want to display onto the nav's controller stack and when you want them to disappear you pop them off.
A common (though sloppy) way of using a nav is to make it a property of your app delegate. Then anywhere in your app you can references it by:
UINavigationController *nav=[[[UIApplication sharedApplication] delegate] navigationController];
The view controller for the first the user sees is held in the nav's topViewController property. If you want to load a view based on a user action in the topViewController.view, you would have something like this:
- (IBAction) loadNextView:(id) sender{ // Action called by a a UI event such as a button press.
UINavigationController *nav=[[[UIApplication sharedApplication] delegate] navigationController];
UIViewController *nextViewController=...// load from nib, connect with IBOutlet, create programmatically
[nav pushViewController:nextView animated:YES];
}
The first view disappears to be replaced by the next one. To return to the first view, you have a method in the next view controller like so:
- (IBAction) unloadSelf:(id) sender{ // Action called by a a UI event such as a button press.
UINavigationController *nav=[[[UIApplication sharedApplication] delegate] navigationController];
[nav popViewControllerAnimated:YES];
}
... and the nav returns you automatically to the previous view regardless of what that view was.
When you first start out, especially if you use Interface Builder, the structure of the app is largely hidden. Behind the scenes all view controllers and their views exist in a hierarchy of some kind that leads back up to the app delegate. You should train yourself to think in hierarchal terms even if it is not immediately obvious how that hierarchy is constructed.
I am sure this is an easy question, but one that has escaped me for some time now.
Say I have a UIViewController, either defined as a root in an XIB or on a stack. At some point in my code I want to replace it with another view controller. Just flat out replace it. How would I do that?
I have tried defining the controller and assigning, but not sure what actually makes it push on the screen with the absence of a navigation controller.
I think when you say that you want to replace the view controller, what you actually mean is that you want to replace the view. Bear in mind that view controllers aren't visible, but every view controller maps to a view, which can become visible by getting added as a subview of a visible view.
Your solution of replacing self.view with the new view controller's view may work in your particular case, but it's probably not the "correct" answer to your question. There are going to be cases where this solution won't work for you.
Let's say you have a simple view based application with no navigation controller and no tab bar controller. In your app delegate you construct an instance of YourFirstViewController, and you call [window addSubview:yourFirstController];. Your view hierarchy now consists of a UIWindow with a single subview -- the view for YourFirstViewController.
Now let's say the user presses a button on that view, which is handled by an IBAction defined in YourFirstViewController. You want to respond by "replacing" YourFirstViewController's view with a view associated with YourSecondViewController. I put "replacing" in quotes because we more commonly present a view by pushing its view controller onto a navigation stack, or calling presentModalViewController:animated: to present the view modally, but let's assume that you've rejected those options for some reason, and you actually do want to manually replace YourFirstViewController's view with YourSecondViewController's view.
This is a simple matter of manipulating the view hierarchy. You want to remove YourFirstViewController's view from its superview (the UIWindow in this case), and you want to add YourSecondViewController's view as a subview to replace it. Your action would therefore look something like this:
- (IBAction)replaceButtonClicked {
UIView *mySuperview = self.view.superview;
YourSecondViewController *secondController = [[YourSecondViewController alloc] init];
[mySuperview addSubview:secondController.view];
[self.view removeFromSuperview];
[secondController release];
}
When we use a methods like -pushViewController:animated: or -presentModalViewController, the receiving controller manipulates the view hierarchy for us. This may make it seem like we're looking at view controllers on the screen, but we're not. We're just looking at a big hierarchy of nested views going all the way up to a UIWindow at the top.
You can present a new view controller modally:
[self presentModalViewController:aViewController animated:YES];
This won't outright replace the current VC, but it will display a new view over the current view.