I have a tabbar application and on the first tab I have a MKMapView. What I want to do is from somewhere else in the application, switch the active tab to the mapview and set the mapview's region based on the data in the previous view (the one with the button to switch to the mapview).
What I've tried is:
[self.tabBarController setSelectedView:0];
UIMapViewController *mapView = [self.tabBarController.viewControllers objectAtIndex:0];
[mapView displayBookmarkAnnotation:bookmark];
This just causes the app to crash unable to find the method I created.
I don't think I've chosen the best path to implement this but I'm really not sure how I should go about it.
[Update]
Casting the controller returned by the tabBarController had no effect.
[Solved]
I was trying to cast a UINavigationController to my mapView
[self.tabBarController setSelectedView:0];
UINavigationController *navController = [self.tabBarController.viewControllers objectAtIndex:0];
//if the tab has other views open, return to mapView
[navController popToRootViewControllerAnimated:YES];
UIMapViewController *mapView = (UIMapViewController *)[navController visibleViewController];
[mapView customMessage:object];
Are you sure the main view controller for that tab is not a UINavigationController? If so, you can get the root view controller for that which should be your UIMapViewController.
It would be good to put a direct reference in the AppDelegate though if you are going to be calling it from elsewhere.
Why not route it through your AppDelegate? The AppDelegate can have a UITabBarController and the MKMapView (both wired through interface builder.) The UIButton handler would then also be in the AppDelegate so that it can call -[UITabBarController setSelectedView:] and -[MKMapView setRegion:].
What you want to do is create a subclass or a category of the UITabBarController that
registers for NotificationCenter events that you define
handles the events with a new selector. I generally use do/did naming convention for them.
When the event comes through you set the selectedIndex.
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.
If the application was previously in the background, when applicationDidBecomeActive is called,how can I optionally refresh the user interface ?
I expect the current view controller is always the initial view controller in storyboard.I can't get the pointer to storyboard in my main AppDelegate.m .
How can I check and determine which view controller is currently showing ?
If you just want a pointer to your storyboard then you can do this:
UIStoryboard *sb = [[[self window] rootViewController] storyboard];
where rootViewController is actually the initial view controller of your storyboard. If you expect this controller to be the current controller (as you say) then you're good to go, but if you want to actually update your UI, then I guess you could post a custom notification from the delegate (inside applicationDidBecomeActive), and register each controller that may be interested to catch it so it can update its UI (or just add self as observer for UIApplicationDidBecomeActiveNotification to catch the same one that your delegate catches...).
PS. If your rootViewController is a UINavigationController you can get the currently showing controller like this:
id currentController = [[[self window] rootViewController] visibleViewController];
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 have a UITabBarController, and one tab is a UINavigationController. I have a search bar that goes to a certain view within the UINavigationController. The problem is that if the first view is not pushed by the UINavigationController, than it crashes because my search doesn't recognize the visibleViewController from this call:
UINavigationController *navController = [self.MainTab.viewControllers objectAtIndex:1];
FirstViewController *fVC = [navController visibleViewController];
What I don't understand is, before this code, I do this:
self.MainTab.selectedIndex = 1;
This code on its own selects the viewController in that tab, where then the view gets loaded to my knowledge. So shouldn't this be enough for the [navController visibleViewController] to get the current viewController? Thanks.
Try topViewController instead of visibleViewController.
FirstViewController *fVC = [navController topViewController];
From what you explain in your question and comments, I understand that your code tries to access an object of type FirstViewController, supposedly the first view to be pushed on to your UINavigationController, when it has not yet been created.
On the other hand, if you first programmatically select the tab, the view is created and everything works fine. Indeed, that view is created in a viewDidLoad method that is run when the tab is selected.
The solution I would suggest is avoiding accessing the UINavigationController visibleViewController directly from your search tab; instead, let your search code access the model (as in Model-View-Controller) for your app and store there the result; then, from the mentioned viewDidLoad method again access the model to read the search result and update/show the UI.
This is the clean solution, IMO. If you want a sort of workaround to your current design, then check the fVC value you get back from visibleViewController and if it is not what expected, then instantiate the view properly.
I hope this helps.
I know this has been answered, but I found another solution that might be helpful. In my case I was handling rotation differently for some viewControllers within my NavigationController, I did the following:
Subclass UINavigationController, then where needed in your new subclass you can access the current visibleViewController's title like so:
- (BOOL)shouldAutorotate
{
if ([[self visibleViewController].title isEqualToString:#"Special Case"]) {
return NO;
}
return YES;
}
This is not specific to rotation, this is just what I used it for. The only thing you have to do is set your self.title for each of the viewControllers you are checking against in their viewDidLoad, if they are set in IB or are not set they will be nil.
I have a TabBarController with 7 Custom ViewControllers and what i am trying to do is have the TabBarController on startup load the first ViewController in its array as well as a ViewController in one of the other tabs.
As far as i understand it the viewDidLoad method for the ViewController's is only called for that tab when it is first selected. Is there a way to force the TabBarController to call a ViewController viewDidLoad method even if its not active?
thx
Just reference the ViewController view:
[myViewController view]
If myViewController's view is nil, then it will be loaded.
Note that even if this approach is working, your app will be affected by the view loading/unloading mechanism which is controlled by the internal run loop logic and not by your app, while the view controller "internal logic" should be initialized by the initWithNib: method which is completely under your control. But this is just a suggestion to avoid strange bugs, anyway the solution proposed is working.
This technique seems to work pretty good. I have an app with a UITabBarController at the bottom with 5 buttons in it. When the user clicks the 3rd button, the viewDidLoad for that view took 5 seconds to do stuff so I used this technique to cause its viewDidLoad to get called when the app starts. I don't want the 3rd view to be displayed; just to be initialized so it shows up instantly when clicked.
I had to subclass the UITabBarController to something like FoohBarController, then in it's viewDidLoad I made a background thread do this:
{
// get a pointer to the 3rd item in the tab bar (0 based)
UINavigationController *navcon = [self.viewControllers objectAtIndex:2];
// get a pointer to the viewController I want to init
CalendarViewController *calendar = [navcon.viewControllers objectAtIndex:0];
// Just ask for the view. This will force the view to load and to initialize
UIView *v = calendar.view;
v = nil; // to remove a compiler warning
}