I will like my application that always starts as the first time I open it. I have several view controllers and when I exit my application and I open it again I see the view controller where I left of. Maybe I have to call the method applicationWillTerminate method.
I use this code to open a new view:
UIViewController *control = [[SomeViewController alloc] initWithNibName:#"SomeViewController"
bundle:nil];
UINavigationController *navControl = [[UINavigationController alloc]
initWithRootViewController:control];
[self presentModalViewController:navControl animated:NO];
[navControl setNavigationBarHidden:YES];
[control release];
[navControl release];
this code works great when linking it to buttons. But when I place that code in the applicationDidBecomeActive method it does not work.
The easiest way is to set UIApplicationExitsOnSuspend in Info.plist.
That really isn't the expected behaviour, though. Users expect to see the app "where they left off", especially if they've only briefly left the app (e.g. because they got a phone call).
Your code snippet adds a view controller, but is unlikely to work since your app delegate is not a UIViewController. It also doesn't do anything about removing the old view controllers.
EDIT: If all you need to do is display a splash screen (or something), then it's something like this:
In -applicationDidEnterBackground:, add a "splash screen" view (not a view controller) to self.window. (iOS takes a "screenshot" after you return from -applicationDidEnterBackground: and uses this in the app-switch animation; you want this to be what the user sees when switching back to your app)
In -applicationWillEnterForeground:, do whatever animations you want and eventually remove the view from the window (call -removeFromSuperview).
EDIT 2: The same will work in -applicationWillResignActive:/-applicationWillBecomeActive:, except this happens on a sleep/wake event, which might not be what you want...
I'd avoid using view controllers for this, because trying to shoehorn a view controller in the view controller hierarchy is likely to be problematic (for example, you have to figure out which VC to present it from, and you have to do the "right thing" if the user backgrounds your app while the VC is on screen, and...)
The reason it doesn't work in applicationDidBecomeActive is that method is only sent to the Application delegate, which doesn't know about presentModalViewController.
I suggest instead that in your appDelegate, implement applicationWillEnterForeground:, which should restore the state to a newly launched application (equivalent to what the state is at the end of application:didFinishLaunchingWithOptions: ).
OR...(edits)
If you just want a certain viewController to run (which is still loaded, right?)...For example, if you have a tab controller and just want to go to the root of the first view controller, put the following code into applicationWillEnterForeground:
UITabBarController * myTabBar = self.tabBarController;
myTabBar.selectedIndex = 0;
[[myTabBar.viewControllers objectAtIndex:0] popToRootViewControllerAnimated:NO];
Temporary solution:
I made my application crash on applicationWillResignActive method and it works. My application needs to run an animation when I launch it. But this works because next time the application runs it starts like the first time I opened it.
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 sure this has been asked countless times, and I've seen similar questions though the answer still eludes me.
I have an application with multiple view controllers and as a good view controller does its own task. However I find myself stuck in that I can't switch from one view controller to another. I've seen many people say "use a navigation controller" but this isn't what I want to use due to the unwanted view elements that are part and parcel to view controller.
I've done the following and have had limited success. The view controller is switched but the view does not load and I get an empty view instead:
- (IBAction)showLogin:(id)sender
{
PPLoginViewController *login = [[PPLoginViewController alloc] initWithNibName:#"PPLoginViewController" bundle:nil];
PPAppDelegate *appDelegate = [UIApplication sharedApplication].delegate;
appDelegate.window.rootViewController = login;
[self.view insertSubview:login.view atIndex:0];
}
Using UINavigationController as a rootViewController is a good tone of creating iOS application.
As i understand unwanted view elements is a navigationBar? You can just hide it manually, setting:
[self.navigationController setNavigationBarHidden:YES];
And about your case, if you want to change you current viewController(targeting iOS 6), you can just present new one:
[self presentViewController:login animated:YES completion:nil];
or add child (Here is nice example to add and remove a child):
[self addChildViewController:login];
Why to set UINavigationController as a root?
1) First of all it makes your application visible viewcontrollers to be well structured. (Especially it is needed on iPhone). You can always get the stack and pop (or move) to any viewController you want.
2) Why I make always make navigation as a root one, because it makes the application more supportable, so to it will cost not so many code changes to add some features to the app.
If you create one (root) viewcontroller with a lot of children, or which presents other viewcontrolls, it will make your code really difficult to support, and make something like gode-object.
Listen to George, UINavigationController is the way to go. Your reasons for not wanting to use it are not valid.
However, the reason your code doesn't work might have to do with the unnecessary line after setting the rootViewController to the login vc.
Per Apple's documentation, setting rootViewController automatically sets the window's view to the view controller's view.
I have a problem with the UINavigationController. It about a client or serverside logout.
The idea for serverside logout is this, every 15 seconds a function is called that checks if the App is still logged in. If that is not the case then jump to the LoginViewController.
The Logout can also happen from the App itself. It executs simular code.
There are three relevant Controllers, LoginViewController is where we want to end up, SignOutController is where the 'Sign out'-Button is located and MainViewController.
Here are the relevant code parts.
First, the UINavigationController gets allcated like this:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
splashScreenViewController_ = [[SplashScreenViewController alloc] initWithNibName:#"SplashScreenViewController" bundle:nil];
uiNav_ = [[UINavigationController alloc] initWithRootViewController:splashScreenViewController_];
uiNav_.navigationBar.barStyle = UIBarStyleBlackTranslucent;
uiNav_.navigationBarHidden = YES;
[window_ setRootViewController:uiNav_];
[window_ makeKeyAndVisible];
return YES;
}
When the 'Sign out'-Button is pressed or the App figures out that the Server has forced a logout, this code is executed (same code, diffrent functions):
LoginViewController *loginView = [[LoginViewController alloc]initWithNibName:#"LoginViewController" bundle:nil];
[self.navigationController pushViewController:loginView animated:YES];
[loginView release];
If its a Serverside Logout it just reloads the MainViewController, every 15 seconds you see the animation of MainViewController sliding in. Its goes in a cycle from there, every 15 seconds it reloads.
If you click the 'Sign out'-Button it jumps to MainViewController instead of LoginViewController and starts the same cycle discribed above.
P.S. I have checked if any importend variable is nil, and I have checked that initalisation code is actually executed.
Edit: I think I did not mention that. My app works 99% of the time. Just one in a while this happen that the Sign-out button does not work and I start this cycle. Normally it works fine.
For the 15 second cycle where a new LoginViewController slides in it just seems you are not stopping to check if the app is logged in after realizing it wasn't. You should have some sort of boolean to store that and cancel the timer or whatever you use.
I don't understand what you say happens when you press the logout button, but I don't think you are making a good user interface.
I suggest you start the application by adding to the navigation controller the loginViewController as root. Then you add without animation the one you want to start with (for example MainViewController). Whenever the application is logged out of the service you pop the view controllers until the first one, which sould be the login one.
You have the method popToRootViewControllerAnimated: for that.
If you want to preserve the splash screen you can set it as the root view controller of the app, and chenge it to the uiNavigationController when you have finished loading.
The timer won't stop automatically just because you've pushed a view on top of another. It will be there until the controller it started on is released, which will only happen after it has been removed from the stack.
Also, you don't need to push MainViewController onto the stack after every check, you'll end up with multiple instances of it, each on top of another.
Also, without really knowing much about the architecture of the app, it would seem like a good idea to make LoginViewController modal, they really can't do anything if they've not logged in right? A modally presented viewcontroller wouldn't be affected by the navigation stack, and would also retain the users navigation stack much easier than having to manually push/pop controllers.
My app downloads data from internet when it starts, during the splash screen.
It does the same when, from the background, it enters in foreground (when the user open the app from the background).
When the app is open, the user can push some views in order to read the informations downloaded.
I want that when the app is open from the background state, the viewControllers are popped until the first view is showed...
I want to do something like this in my AppDelegate:
while ([self.view isNotMainView]) //of course this method doesn't exists
{ [self.navigationController popViewControllerAnimated:NO]; }
is it possible?
Thanks
Just use:
[self.navigationController popToRootViewControllerAnimated:NO];
Hope that Helps!
hope Following link will help...
How are people popping their UINavigationController stacks under a UITabBarController?
You can keep a reference or Current navigation controller in your appdelegate OR you can write this in you viewDidUnload OR viewWillDisapper for popping navigation to root when application goes to background.
You could just compare the view against your main view if you have a reference hanging around:
while (self.view != myMainView)
etc. (Assuming that self.view is the correct reference as well.)
I am a relatively new iPhone app developer so my knowledge is a little sketchy, so please forgive me if this is a bit of a trivial question.
I have a navigation app which drills between table views by calling pushViewController on the navigationController object
I have one particular section which pushes new view controllers sequentially as the user goes through the interface. The view controllers are all subclassed from UIViewController.
It all works fine until it gets to the end, where the idea is the user presses a "Finish" button and is returned to the root view controller (main menu).
So on the button press I call:
[[self navigationController] popToRootViewControllerAnimated:YES];
And it crashes.
I am a bit worried this could be a big problem as this definitly worked at some point but it is now always failing.
Can anyone give any ideas/advice?
Some suggestions:
Before calling popToRootViewControllerAnimated: confirm that the RootViewController does actually exist. If it died somewhere along the line, calling the method will cause a crash.
Check the – viewWillDisappear: and – viewDidDisappear: methods of your last view to make sure you're not doing something dangerous there.
Not sure if popping a view causes it to always deallocate but check the dealloc method of the views and their controllers to make sure your not over-releasing something.
One mistake I've seen a lot is releasing objects in the data model from controllers. When another controller (in this case the RootViewController) tries to access the data model the app crashes.
It sound's like you need how to use the Xcode debugger. Type in debugger in Xcode help to get pointers.
You should not be using popToRootViewController in your viewWillDisappear.
Instead if you want to pop to root controller on your pressing the back button, you should replace the back button by your own and add an action to it. Try doing something like ::
UIBarButtonItem *back = [[UIBarButtonItem alloc] initWithTitle:#"back"
style:UIBarButtonItemStyleBordered
target:self
action:#selector(goBack:)];
self.navigationItem.leftBarButtonItem = back;
and then handle the action as ::
- (void) goBack:(id)sender
{
// pop to root view controller
[self.navigationController popToRootViewControllerAnimated:YES];
}
As the others have commented, the first step is to run this is debug mode and figure out where and why you are crashing.
The most common type of crash is using a deallocated object (EXEC_BAD_ACCESS). Have you run the static analyzer? Are you properly retaining your object references?