my project first used the Three20 frame work for handling navigation.But due to some problems i ha to remove the three20 part.So im redesigning my app.
what im trying to do is show a detail view when user touches a button.I created a new mainwindow as there was none earlier.It does not have a navigation controller.
i used
DetailViewController *detailViewController=[[DetailViewController alloc] init];
[self.navigationController pushviewController:detailviewController animated:YES]
in the buttos touch up event.
but when i run the app nothings hapens on button touch.No warnings or errors are shown.
Ive done this in other apps but it just doesnt work here.
Since you are not using a UINavigationController, the navigationController property of the your UIViewController will remain nil. "Compile-wise" there's no problem, since the property exists, but the compiler does not know the property will remain nil, hence no warnings/errors are shown.
Sending a message to a nil object is allowed in Objective-C, hence the code doesn't crash and does nothing when being run.
If you want to get your code up & running, you'll need to put the root UIViewController in a UINavigationController. Once the UIViewController is shown in a UINavigationController, the property will be set to the UINavigationController automatically.
Edit: You could use something like this, instead of showing someController, "encapsulate" it in a UINavigationController and show that controller.
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:someController];
Related
I am a newbie to iOS world and have started building custom code on top of a templated code.
So excuse me for the obvious.
The View chain starts with a MainWindow.xib which contains a App Delegate Object, a Window Object and Application ViewController. I dont understand why those objects are needed over there. But what I understand, I need to mention starting ViewController in the "Nib Name" Property to initiate my custom View Controller (called "EmptyViewController"). Its a dummy view controller, just there to avoid crash to happen as a result of missing valid viewcontroller.
I initiate a separate Modal View Controller(MainViewController) inside didFinishLaunchingWithOptions.
Code for initiating modal View Controller --
self.window.rootViewController = self.viewController;
mainView = [[MainViewController alloc] initWithNibName:#"MainViewController" bundle:nil];
// present the viewcontroller
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:mainView];
[self.viewController presentModalViewController:navController animated:NO];
// release it, because it's retained as modalViewController
[navController release];
I do not put this MainViewController inside MainWindow.xib as I want to have navigation at the root of MainViewController.
Inside MainViewController, I push HelpViewController when "help" button is pressed.
But HelpViewController does not show any navigation bar. I do not understand why?
Code for Pushing Navigation bar --
HelpViewController *helpVC = [[HelpViewController alloc] init];
[self.navigationController pushViewController:helpVC animated:YES];
[helpVC release];
So I would like to understand --
1) Why is MainWindow.xib needed? Can I remove it? (Note: I tried to remove it, but then I get blank screen)
1.a) Why are all the controls/objects App Delegate Object, a Window Object and Application ViewController objects needed?
2) Why doesnt HelpViewController show Navigation bar?
3) Another thing I noticed, if I say self.presentingViewController, EmptyViewController handle is returned while popViewController returns me back to MainViewController.
Thanks
The App Delegate simply implements some app-level 'callbacks' by which iOS communicates with your own code. In main.m you can see how iOS is told which of your classes implements UIApplicationDelegate. iOS creates an instance of this class and call these delegate methods ('callback') whenever appropriate (e.g. when the app goes to background).
The Window is something iOS provides, your app needs to tell what to display on it. And, as you saw, this is usually done in didFinishLaunchingWithOptions (which is called by iOS to inform your app things are ready to get started).
A View Controller is a class that handles states of stuff you show on the Window. You don't show stuff directly on the Window, but instead use Views. Every View Controller has a View with UI elements.
The XIB or NIB is a UI description/layout file. A XIB and View are linked together; you need to tell the XIB to which View Controller member (e.g. a UILabel) a UI element belongs, and you tell the XIB which View Controller method to call on a certain UI event (e.g. user taps on a button).
These are the basics. I'm aware it does not answer all your questions; I suggest you read the very good Apple documentation. Don't try to understand everything immediately as things, as you're experiencing, indeed can seem illogical at start.
I'm developing my first iPhone app, which is a navigation based one. I want to know how I can use icons/buttons like this app in the root view to control navigation instead of the default table cell view.
I would appreciate some step by step guide since I'm sort of newbie and didn't get how to do this, reading the documentations, or similar questions.
Rather than starting with a Navigation based app, start with a window based app and create an instance of UINavigationController in app delegate (in method appDidFinishLaunching) and set any UIviewController as it's root view controller. You can then do whatever customizations in that view controller
Finally set the navigationController as rootviewController of you application window.
UIViewController *myCustomRootViewController = [[UIViewController alloc] init];
UINavigationController *myNavController = [[UINavigationController alloc] initWithRootViewController:myCustomRootViewController];
[myCustomRootViewController release];
self.window.rootViewController = myNavController;
[myNavController release];
You really need to use google, or anywhere else on Stack Overflow before you ask a question. I found this in a minute. If you're adding to a navigation controller (which is what handles views in a table view), then use – pushViewController:animated: instead of presentModalViewController:animated: And after you push or present a view controller, don't forget to release it if you are not using automatic reference counting.
i created a navigation based project but instead of tableview i added a new view with a button to navigate to the other view.. my button code is as shown below but whenever i run it the application doesn't run?? is the code wrong or navigation based application only work with tableview??
-(IBAction)clickMe:(id)sender
chdDetails *details=[[chdDetails dalloc]initWithNibName:#"chdDetails" bundle:nil];
[self.navigationController pushViewController:details animated:YES];
[details release];
details=nil;
It says "[[chdDetails dalloc]initW.... instead of alloc. is that a copy-waste typo?
No a navigationCOntroller will work with any viewController, you don't even need the navigationbar. I bet most application are navigationBased but you don't even see it.
[self.navigationController.navigationBar setHidden:YES]
Will do that.
Try placing a breakpoint in the clickMe method to test if it even gets called. What does this mean: "the application doesn't run??" is there an error message? Have you hooked the button up in IB? Is chdDetails a subclass of UIViewController? etc. etc.
Is chdDetails an UIViewController or an UIView? You can't push an UIView on an UINavigationController, only controllers.
I recently started a project, using Apple's Utility Application example project. In the example project, there's an info button that shows an instance of FlipSideView. If you know the Weather.app, you know what the button acts like.
I then changed the MainWindow.xib to contain a scrollview in the middle of the window and a page-control view at the bottom of the window (again, like the Weather.app). The scrollview gets filled with instances of MainView. When I then clicked the info button, the FlipSideView would show, but only in the area that was previously filled by the MainView instance – this means that the page-control view on the bottom of the page still showed when the FlipSideView instance got loaded.
So, I thought that I would simply add a UIViewController for the top-most window, which is the one declared inside the AppDelegate created along side with the project. So, I created a subclass of UIViewController, put an instance of it inside MainWindow.xib and connected it's view outlet to the UIWindow declared as window inside the app delegate. I also changed the button's action, so that it know sends a message to the MainWindowController instance. The message does get sent (I checked with NSLog() statements), but the FlipSideView doesn't get shown. Here's the relevant (?) code:
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideView" bundle:nil];
controller.delegate = self;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
Why's this not working from inside of MainWindowController, but the exact same code is working from inside of MainViewController? I've uploaded the entire project here for you to be able to see the whole thing.
Thanks for help!
-- Ry
EDIT: I think it might be related to me attaching the UIViewController's view outlet to an UIWindow instance. I now connect it to a UIView, and it's working perfectly well.
For the record, the answer has been added in the question. Ryyst said:
I think it might be related to me
attaching the UIViewController's view
outlet to an UIWindow instance. I now
connect it to a UIView, and it's
working perfectly well.
I'm experimenting with ViewControllers & NavigationControllers in Interface Builder trying to get a better grasp of what's tied to what and why... I'm struggling with a scenario that has confused me. Hopefully someone can set me straight...
Say I start with your typical iPhone template View-Based Application and I display a view which is handled by view controller (viewController). Then after a certain event I'd like to replace that view with a "typical" Navigation-Based View (rootVC). I'd like to create as much as possible in IB. My questions have to do with how to show rootVC and remove all traces of the previous viewController as user will never need to return and where/how to wire in the navController in IB. Currently when it's time to show the rootVC I do the following in my viewController:
RootVC *rvc = [[RootVC alloc] initWithNibName:#"RootVC" bundle:nil];
[rvc.view setFrame:[[UIScreen mainScreen] applicationFrame]];
ViewTestAppDelegate *appDelegate = (ViewTestAppDelegate *)[[UIApplication sharedApplication] delegate];
self.rootVC = rvc;
[rvc release];
[appDelegate.viewController.view removeFromSuperview];
[appDelegate.window addSubview:rootVC.view];
[appDelegate.viewController release];
rootVC displays except viewController still has a retain count of 1?!?
Also, where should rootVC's navigationController be instantiated? Having started with the View-Based template the MainWindow.xib contains an object for the viewController (which has its own ViewController.xib) an appDelegate and a UIWindow. My RootVC.xib contains a UITableView. Do I need yet another intermediary view controller that will have another ApplicationDelegate object that I wire up to a UIWindow object and a UINavigationController? The View Controller that comes along with IB's Navigation Controller object would then be set to my RootVC class?
Sorry for the verbosity. It's difficult for me to explain. Because some objects in IB are proxies and some are "real" it's sometimes confusing (to me) when trying "new" things out what's required, where & when. Basically I want to know to go about setting up one view leading to another with no way back to first view. 2nd view basically becomes the "main" root spawning off in many directions...
I would recommend using the navigation-based iPhone application template and presenting your one-time view as a modal view on top of the root view.
I was able to figure it out by putting a reference to the viewController in the MainWindow nib and then autoreleasing the viewController after I added the navigationController & rootVC to the UIWindow. Learned another thing or two about IB along the way. Pretty powerful...