I've run into a problem with my Project.
Every time I try to access my UINavigationController from a Pushed UIViewController, I get "(null)" as a return.
So this is my project is structured:
1. AppDelegate.m initalises UINavigation Controller
2. UINavigation Controller starts with Welcome Page
3. Welcome Page Pushes New UIViewController on Button Press
4. UIViewController returns (null) when self.navigationController called
OK, so here's some code, in my Welcome Page I'm calling this:
MyClass *theChatRoom = [[MyClass alloc] initWithNibName:#"ChatRoom" bundle:nil];
[theChatRoom setTitle:[unitCode text]];
[self.navigationController pushViewController:theChatRoom animated:YES];
Which works fine, it pushes the new View Controller.
But then in MyClass.m :
#implementation MyClass
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
NSLog([NSString stringWithFormat:#"%#",self.navigationController]);
}
return self;
}
This returns (null)
What am I doing wrong?
According the documentation, the navigationController of UIViewController:
This property is nil if the view controller is not embedded inside a
navigation controller.
That's said, if you access the navigationController before embedding into the UINavigationController(not push yet), it will return nil. So you can access it in the viewDidLoad but no in - (id)initWithNibName:bundle:.
Related
I'm trying to make a button take me to a new UIViewController based on the content of a textField, but when I run it and hit the button (with the right condition in the text field to take me to the new UIViewController), the screen blacks out. This is what I wrote in my .h and .m files. Can anyone help me (Im using storyboards)
#interface ViewController : UIViewController
- (IBAction)boton:(id)sender;
#property (strong, nonatomic) IBOutlet UITextField *texto;
#end
#import "ViewController.h"
#import "ViewController2.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize texto;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)boton:(id)sender {
if ([texto.text isEqualToString:#"1"]) {
ViewController2 *vc1=[[ViewController2 alloc]init];
[self presentViewController:vc1 animated:YES completion:nil];
}
}
#end
As you say the screen is blacking out, I expect your viewController is getting initialised without a view.
To initialise with a view hierarchy from a xib(nib) file:
- (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle
where nibName can be nil if it shares it's name with the View Controller, and nibBundle can be nil it the nib is in the main bundle.
i.e....
ViewController2 *vc2;
vc2 = [[ViewController2 alloc] initWithNibName:nil
bundle:nil];
where the xib file is named ViewController2.xib
To initialise from a storyboard:
UIStoryboard *storyboard = self.storyboard;
vc2 = [storyboard instantiateViewControllerWithIdentifier:#"ViewController2"];
(you need to set up a viewController in storyboard and give it a matching identifier)
To initialise with neither storyboard or xib, you should override your view controller's - (void)loadView, create a view and assign it to self.view.
Update
In answer to your comment - the UIStoryboard... and ViewController2 *vc2= ... code would go into your button code (in your case it you would replace / adapt the line containing vc1=.... It would look like this:
- (IBAction)boton:(id)sender {
if ([texto.text isEqualToString:#"1"]) {
ViewController2 *vc2;
UIStoryboard *storyboard = self.storyboard;
vc2 = [storyboard instantiateViewControllerWithIdentifier:#"ViewController2"];
[self presentViewController:vc2 animated:YES completion:nil];
}
You will need to have created a storyboard scene in your storyboard with a viewController whose custom class is ViewController2 and identifier is "ViewController2". The identifier name is arbitrary, but must match the identifier string you use in your code.
As you are using storyboards, an alternative way to do this is to create a modal segue from the 'ViewController' scene to a 'ViewController2' scene, give it an identifier, and use performSegueWithIdentifier in your button method.
I learn the ObjC program flow, so far I understand that chain begins in main.m->UIApplicationMain->AppDelegate->ViewController
The point I don't understand is to which method inside the ViewController the AppDelegate class transfers the focus...
I feel it is critical to understand this topic, so would be thankful for any clarifications.
I have this code of Appdelegate.m -
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions: (NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
MasterViewController *masterViewController = [[MasterViewController alloc] init];
self.navigationController = [[UINavigationController alloc] initWithRootViewController: masterViewController];
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];
return YES;
and inside the ViewController there are these methods -
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self.navigationController setNavigationBarHidden:YES animated: NO];
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear: animated];
}
and others methods...
My questions are
To what method AppDelegate transfers control in MasterViewController. And does the control come back after MasterViewController "finished" its job or it is just looped?
How MasterViewController gets the xib name for initialisation (is it the same name as m file? i.e. what does it mean - nibNameOrNil bundle:nibBundleOrNil)
I see navigation controller involvement, however I don't understand how it is connected to viewcontroller....
If you catch my misunderstanding points - please be patient to explain... I feel that after this point I will be able to start...
(1) You're thinking about the logical flow in a procedural sort of way. The main run loop dispatches events down the responder chain. Your MasterViewController doesn't really 'finish'.
(2) The designated initializer for UIViewController is initWithNibName:bundle:. Your use of init here will not touch any associated nib file. If you wish to initialize MasterViewController from the nib, then you must use the designated initializer, e.g.
MasterViewController *masterViewController = [[MasterViewController alloc] initWithNibName:#"your-nib-name-goes-here" bundle:nil];
nibNameOrNil and nibBundleOrNil are just parameter names for the method. It's a tip to you that they may be nil. Take a look at the documentation for how the method behaves when those params are nil.
(3) UINavigationController is a subclass of UIViewController that presents content hierarchically. In this case, the application's window's root view controller is a navigation controller. In turn, that navigation controller's root view controller is your MasterViewController instance.
The documentation for UINavigationController describes it well.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
Everything works fine. The code above is standard written by compiler. Nothing strange. I put breakpoints there in my viewControllers just to see how things go.
Sometimes the function is called. Sometimes it's not.
'
In all cases things work fine. But what would be the circumstances where that function is not called?
Yes, I am using XIB for all those viewControllers.
I notice that viewControllers directly under the navigationViewController is the one where initWithNibName doesn't break. I wonder why.
When your NSViewController is defined in a xib file (usually as an IBOutlet), initWithNibName:bundle: is not called, rather initWithCoder: gets called. This is the case when you use Interface Builder to set your NSViewController as part of UITabBarController(for UIViewController) or UINavigationController, and almost always when using Storyboards.
Or you can try this one also:
myViewController *objMyViewController = [[MyViewController alloc] initWithNibName:#"WebViewController_iPhone" bundle:nil];
objMyViewController.managedObjectContext = self.managedObjectContext;
navController = [[UINavigationController alloc] initWithRootViewController:objMyViewController];
[self.window setRootViewController:navController];
[window makeKeyAndVisible];
I have a file, called Map:
#interface Map : UIViewController<MKMapViewDelegate> {
IBOutlet MKMapView *map;
}
In interfaceBuider Map starts when the tab is clicked:
Map opens a UITableViewController when clicking and this UITableView opens another UITableViewController.
So what I want now is in the last UITableViewController, when back button is pressed, back to map. I never change the tab, I'm always at "Plano"
so, in Navigation.m I have:
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
And in my secondUITableView.m:
Navigation *aMap = [[Navigation alloc]initWithNibName:#"Map" bundle:nil];
[self.navigationController popToViewController:aMap animated:YES];
And what the error:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Tried to pop to a view controller that doesn't exist.'
How can I do this?
Thank you in advance
EDIT :
For back - root
[self.navigationController popToRootViewControllerAnimated:YES];
For back
[self.navigationController popViewControllerAnimated:YES];
I'm trying to build a Cocoa app for OSX Lion.
I have this line in my AppController code:
self.viewController = [[LoginViewController alloc] initWithNibName:#"LoginViewController" bundle:nil appController:self];
[_view addSubview:[_viewController view]];
[[_viewController view] setFrame:[_view bounds]];
LoginViewController looks like this:
#implementation LoginViewController
#synthesize appController = _appController;
- (id) initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil appController:(AppController *)appController {
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
[self setAppController:appController];
NSLog(#"Appcontroller init: %#", _appController);
}
return self;
}
- (IBAction)login:(id)sender {
NSLog(#"Appcontroller login: %#", _appController);
}
The login method is connected to a button click.
Log:
2012-05-23 12:45:49.574 QBLoader[3241:503] Appcontroller init: <AppController: 0x7fe2ab210440>
2012-05-23 12:45:52.085 QBLoader[3241:503] Appcontroller login: (null)
Why is the second log line null?
Since you indicated there is more than one instance of LoginViewController, I would check your xibs to see if you have created an object of that type anywhere. In particular I would start with the xib where you wire up the -login: action. If you only have one instance of AppController, a common method is to create the object in your MainMenu.xib and attach it to an outlet in your app's delegate. Then you can use something like [[NSApp delegate] appController] to access it.