Any help is appreciated ! It's several days I'm fighting w/o results.
The scenario:
I and iPad application have a SplitViewController that shows 2 controllersViews (Root on the left e Detail on the right)
The Root allows a recursive navigation (tree that could be several drilldown levels) and I'm calling every time the same controller class (UITableView) pushing always in the controller stack). When the user taps a cell (left side), the detail view (right side) shows the information.
Keep in mind that the detail view controller is not always the same class: it means that I'm allocating (and releasing) programmatically several detailView controllers according the kind of information I have to display.
Here the fragment:
UIViewController <ItemGenericViewController> *newDetailViewController = [[NSClassFromString(cntrClass) alloc] initWithNibName:cntrXib bundle:nil];
//the detailViewController has been defined in the head section as ItemGenericViewController
//each detailViewController is a subclass of ItemGenericViewController
detailViewController = newDetailViewController;
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:detailViewController];
// Update the split view controller's view controllers array.
NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, nav, nil];
self.splitViewController.viewControllers = viewControllers;
[nav release];
[viewControllers release];
[detailViewController release];
Everything is working fine until a memory warning arises.
From that moment if I try to display a new detailViewcontroller the "connection" in the SplitViewController, between the RootController and the detailController, seems vanished. The result is: nothing appear on the right part of the splitController.
In the mean time if I navigate to parent level in the root controller the situation still failing.
For your information each time I push in the stack a new RootController instance (left column) I'm releasing the same controller (to save memory as usual) and I suspect, after receiving the memory warning, iOS is trying to free itself memory and my "history" disappear and the related connection, throught the split controller, too.
Is a nightmare ;-)
Do you have any suggestion ?
Thanks
Dario
I had a similar problem to you (maybe even worse - 16 combinations of possible view switches)... But I believe i have solved it right now.
So, i believe you have used Apple's example for view switching (I have, with modifications), and if you have so, problem is that "root" splitViewController (from MainWindow.xib) get's "niled" as default behavior when memory warning. And even if you add new array of view controllers to it, it will not cause any change (and even worse, it will not show any sign of warning). And solution is to check is it nil, and if is, to reinitialize it.
here is the code, using example from above:
UIViewController <ItemGenericViewController> *newDetailViewController = [[NSClassFromString(cntrClass) alloc] initWithNibName:cntrXib bundle:nil];
//the detailViewController has been defined in the head section as ItemGenericViewController
//each detailViewController is a subclass of ItemGenericViewController
detailViewController = newDetailViewController;
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:detailViewController];
// Update the split view controller's view controllers array.
NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, nav, nil];
/**** Milos Edit ****/
if (self.splitViewController == nil) {
// I'm keeping reference in app delegate, but any way to reinitialize splitViewController is OK
self.splitViewController = delegate.splitViewController;
}
/**** end of edit ****/
self.splitViewController.viewControllers = viewControllers;
[nav release];
[viewControllers release];
[detailViewController release];
Hope it will be helpful.
Cheers
Milos
Related
I have a UINavigationController object (named LoginNav) which consists of ViewController1 & ViewController2, my iPad app starts by loading a UISplitViewController subclass (named mainSplitViewController) and then presenting LoginNav modally on top of it (this is by the way done in didFinishLaunchingWithOptions method of AppDelegate like this:
[self.mainSplitViewController presentModalViewController:LoginNav animated:YES];).
Once ViewController1 is shown, I tap a UIButton in it to push ViewController2, when I finish working in ViewController2 I tap a UIButton in it to call [self.navigationController dismissModalViewControllerAnimated:YES]; to dismiss LoginNav with both of its view controllers and show mainSplitViewController's contents.
There is a dealloc method in both ViewController1 & ViewController2 with NSLog statement in each one, once loginNav is dismissed, the NSLogs never get fired, but doing [self.navigationController.viewControllers objectAtIndex:0] release]; & [self.navigationController.viewControllers objectAtIndex:1] release]; right after [self.navigationController dismissModalViewControllerAnimated:YES]; fires both NSLogs.
I commented out the above two release statements, then I launched the Allocations instrument, and launched the app again and pushed ViewController2 then dismissed loginNav as described above, and looked at Live Bytes column (All Allocations value ) it was 6.9 MB right after the dismissal of loginNav, then I did this step again but in this case using the two release statements, I got exactly a 6.9 MB value on Live Bytes column.
Two Questions:
1) why do not the dealloc methods of ViewController1 & ViewController2 never get fired after the dismissal of the navigation controller LoginNav that holds them ? and is it correct to do the above two release statements to release these view controllers ?
2) why releasing ViewController1 & ViewController2 does not free up memory ?
p.s. there is no single variable (or IBOutlet) being held in memory in both ViewController1 & ViewController2, everything is released in both of them.
These kinds of issues are nearly impossible to troubleshoot without seeing all your code. When you manage memory manually, there are multiple areas that you can go wrong. For example the following code will leak:
- (void)didSelectSomethingInViewControllerOne
{
ViewController2 *vc2 = [[ViewController2 alloc] init];
[self.navigationController pushViewController:vc2 animated:YES];
}
In this case you have allocated the object and thus have ownership of it. Then the nav controller takes ownership of it. When you pop the controller from the navigation stack, the navigation controller relinquishes ownership of it, but you never did, so it still has a retain count of 1 and won't get deallocated.
Relinquishing ownership of the controllers later in your code (like after dismissing the modal view) is a bad idea. It makes it difficult to analyze ownership when your releases are all over the place. As soon as the navigation controller has ownership you can release the object you allocated, as you do not intend to use it in the future:
- (void)didSelectSomethingInViewControllerOne
{
ViewController2 *vc2 = [[ViewController2 alloc] init];
[self.navigationController pushViewController:vc2 animated:YES];
[vc2 release];
}
The situation above can have nothing to do with your problem. Your problem may reside in many different areas. Which is why troubleshooting memory management problems is difficult. Without seeing source code.
Consider transitioning your project to ARC:
http://developer.apple.com/library/ios/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html
Another thing you might have fallen foul of is a retained property (such as a delegate) in your LoginNav.
I hope an easy question (but I can't solve it :)) I have 2 views, On view 1 I have UILabels that I change the text on with a button click, if I navigate to view 2 and then go back to view 1 the text is reset.
Is there any way to retain the text on the label when the view is changed?
Originally I used:
-(IBAction) napButton:
(id) sender{ nap *nap1 = [[nap alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:nap1 animated:YES];
this performed a simple view switch. With the suggestion below I changed this to:
-(IBAction) napButton:
(id) sender{ nap *nap1 = [[nap alloc] initWithNibName:#"nap" bundle:nil];
[self.navigationController pushViewController:nap1];
[nap1 release]; } }
The button performs no action and I get warning UINavigationController may not respond to -pushViewController
use UINavigationController. In a memory constrained device this is the best way to push or pop new views while preserving data or state in previous view.
An instance of UINavigationController can be created either in code or in an XIB file with relative ease. It’s thought of as a stack: it has a root view controller, and then new view controllers can be pushed onto the stack (often when the user taps on a row in a table) or popped off the stack (often by pressing the back button).
There are 4our methods are used to navigate user through the stack:
– pushViewController:animated:
– popViewControllerAnimated:
– popToRootViewControllerAnimated:
– popToViewController:animated:
For example if you want to move from view1 to view2, you need to do this from view1 -
SecondViewController *secondView = [[SecondViewController alloc]
initWithNibName:#"SecondViewController" bundle:nil];
[self.navigationController pushViewController:secondView];
[secondView release];
to move back to the previous state, i.e. from view2 to view1, you need to do this from view2 -
[self.navigationController popViewControllerAnimated:YES];
This should solve your problem in the most efficient way.
Imagine that we have multiview apllication which is controlled by Navigation Controller. We go from the first view to second by using pushViewController method and that's not a problem but then we need to move to the third view. And the third one is a view which looks like a TabBar. How do we do that? The third view is supposed to be controlled by TabBarController, isn't it?
So how to pass the control? I declared an outlet UITabBarController * tbc and connected it to TabBarController in xib file and then i tried this in viewDidLoad:
tbc = [[UITabBarController alloc]init];
and it shows nothing.
Your help is highly appreciated
It's a bit wierd. Its more standard to have a tabBarController that switches views and some of those views may be navigation controllers. But ...
Create the UITabBarController and push it.
NSMutableArray *viewControllers = [[NSMutableArray alloc] init];
// create someView
[viewControllers addObject:someView];
// create someView2
[viewControllers addObject:someView2];
UITabBarController *tabController = [[UITabBarController alloc] init];
[tabController setViewControllers:viewControllers];
[[self navigationController] pushViewController:tabController animated:YES];
Then, from the tabBarContoller view, based on some action, you can choose to pop it:
[self.navigationController popViewControllerAnimated: NO];
You can wire it up in the storyboard editor in the latest version of Xcode.
However, since this is very much non-standard use of the controls, you would need a very good reason as to why you would want a UI like this.
And even then, Apple's review process might turn your app down if the interface is clunky.
I have an aplication which initially there's a TabBarController, each tab is a ViewController and every one has a button which calls other controllers.
So how am I supose to structure this? Having one main rootviewController (if so, how?)? Or calling in the appdelegate only the tabBarController and in each the viewControllers inside the tab call the other controllers?
What's the best way so I can advance, go back and transition views nimbly?
Don't know if I made myself clear...
Thanks guys.
Generally you will start with the Template called "Tab Bar Application" and as of Xcode 4 starts by loading the MainWindow Nib, which hold a tab bar and the tab bar is set up in IB to have 2 view controllers, called "FirstViewController", and "SecondViewController"...
You can follow that pattern if it suites you, otherwise you may want to start with a view based application and add your own tab bar. I personally find it to be easier to control the tab bar, through the UITabBarDelegate, especially if you plan to do anything slightly esoteric.
Edit:
Basically one of two ways, if you plan to load a Navigation controller stack, or a single modal view.
1)
ThirdViewController * controller = [[ThirdViewController alloc] initWithNibName:#"ThirdViewController" bundle:nil];
UINavigationController * myNavigationController = [[UINavigationController alloc] initWithRootViewController:controller];
[self presentModalViewController:myNavigationController animated:YES];
[controller release];
[myNavigationController release];
2)
ThirdViewController * controller = [[ThirdViewController alloc] initWithNibName:#"ThirdViewController" bundle:nil];
[self presentModalViewController:controller animated:YES];
[controller release];
either way get back to the Tab environment by calling the following on the view controller that is calling present modal.
[self
dismissModalViewControllerAnimated:YES];
I'm having a problem with an iPhone App using UINavigationController. When I'm using pushNavigationController, it works fine. The iPhone does its animation while switching to the next ViewController. But when using an array of ViewControllers and the setViewControllers method, it has a glitch in the animation which can grow into a clearly visible animation bug.
The following snippet is called in the root ViewController. Depending on a condition it should either switch to ViewController1, or it should directly go to ViewController2. In the latter case the user can navigate back to vc1, then to the root.
NSMutableArray* viewControllers = [NSMutableArray arrayWithCapacity:2];
// put us on the stack
[viewControllers addObject:self];
// add first VC
AuthentificationViewController* authentificationViewController =
[[[AuthentificationViewController alloc] initWithNibName:#"AuthentificationViewController" bundle:nil] autorelease];
[viewControllers addObject:authentificationViewController];
if (someCondition == YES)
{
UserAssignmentsListViewController* userAssignmentsListViewController =
[[[UserAssignmentsListViewController alloc] initWithNibName:#"UserAssignmentsOverviewViewController" bundle:nil] autorelease];
[viewControllers addObject:userAssignmentsListViewController];
}
[self.navigationController
setViewControllers:[NSArray arrayWithArray:viewControllers] animated:YES];
As you can see I'll add the first and maybe the second VC to the array, finally setting the navigationController stack with animation. This works properly if I only add the first controller. But in the case where the animation should go to the 2nd controller, the navigation bar's title won't be "flying in". Instead there is an empty title until the animation is finished. And, even worse, if I replace the navbar title with a custom button, this button will be displayed in the upper left corner until the animation is finished. That's quite a displaying bug.
I tried to use a workaround with multiple pushViewController methods, but the animation doesn't look / feel right. I want the navigation to do its animation in the same way as pushViewController does. The only difference here is, that I don't add a VC but set the whole stack at once. Is there another workaround here, or could this be considered as a framework's bug? I thought about using only pushNavController for VC2, then somehow insert VC1 into the stack, but that doesn't seem possible.
Thanks for all hints and advices. :-)
Technical data: I'm using iOS 4.2, compiling for 4.0.
Finally I found the solution. The mistake was that the new top-level NavigationController has not been initialized and loaded properly until the animation is done. In my case, UserAssignmentsListViewController has a viewDidLoad method that will not be called until animation is done, but it sets the navigation title (here: a UIButton). Therefore the animation fails.
The solution is to refer to an already initialized view controller when it comes to pushing it to the stack. So initialize our top-level VC somewhere:
// initialize our top-level controller
ViewController* viewController2 = [[[ViewController alloc]
initWithNibName:#"ViewController" bundle:nil] autorelease];
Then when pushing two or more VCs to the stack, the top level one is already initialized and the animation works (following the example from my original question):
NSMutableArray* viewControllers = [NSMutableArray arrayWithCapacity:2];
// put us on the stack, too
[viewControllers addObject:self];
ViewController* viewController1 = [[[ViewController alloc]
initWithNibName:#"ViewController" bundle:nil] autorelease];
[viewControllers addObject:viewController1];
if (someCondition == YES)
{
[viewControllers addObject:viewController2];
}
[self.navigationController
setViewControllers:[NSArray arrayWithArray:viewControllers] animated:YES];