I have two class:
MeuPrimeiroViewController.h/.m
MeuSegundoViewController.h/.m
I have this code:
MeuPrimeiroViewController.h
- (IBAction)botao:(id)sender;
MeuPrimeiroViewController.m
#import "MeuPrimeiroViewController.h"
#import "MeuSegundoViewController.h"
- (IBAction)botao:(id)sender{
MeuSegundoViewController *segundo = [[MeuSegundoViewController alloc] init];
UIWindow *window = [[UIApplication sharedApplication] keyWindow];
UIView *view = segundo.view;
[window addSubview:view];
}
This command works great, but in the 'SegundoViewController' I have this code:
MeuSegundoViewController.h
- (IBAction)botaoback:(id)sender;
MeuSegundoViewController.m
- (IBAction)botaoback:(id)sender{
NSLog(#"Back messange");
}
But the console log don't return any messanges, and the simulator returns me to the main.m file, why?
When you do:
[window addSubview:view];
The view belonging to MeuSegundoViewController is retained by its new superview (the window), but the view controller instance segundo isn't - and it gets destroyed. So, when you press the button you get an exception because the segundo instance can't be called.
I doubt you really want to be adding the view as a subview of the window. It would be much better to be adding it as a subview of the MeuPrimeiroViewController view, or to have a navigation controller and push both of the view controllers into it. If you use the navigation controller then it will retain the view controllers (and prevent the crash). If you use MeuPrimeiroViewController then call:
[self addChildViewController:segundo];
if you continue to use the window then you need something to retain the view controller (and there is no good obvious choice).
Related
I'm not using a navigation controller or a tab bar controller, I'm not using the push/pop method or presenting views modally. In my main view controller, I am adding a view controller like so:
UIViewController *nextController;
nextController = [[GamePlayViewController alloc] initWithNibName:#"GamePlayView" bundle:nil];
[nextController performSelector:#selector(setDelegate:) withObject:self];
temporaryController = nextController;
[self.view addSubview:nextController.view];
This view controller follows a delegate protocol and when the user is finished in this game view, this code is called:
[delegate backToMenu:self];
which calls this function in the app's main view controller:
- (void)backToMenu:(GamePlayViewController *)sender {
NSLog(#"back to menu");
[temporaryController.view removeFromSuperview];
}
Removing the view with removeFromSuperview seems to get rid of the view only, but I can see due to NSLogging that code is still executing in the .m file of that removed view. The view is still in in the app's memory. It has not been discarded as I had hoped.
"Release" is an old relic never to be used with ARC, so how can I entirely remove the viewController that was created with alloc/initWithNibName?
Thanks!
You should also be using the view controller life cycle methods.
Adding:
GamePlayViewController *nextController = [[GamePlayViewController alloc] initWithNibName:#"GamePlayView" bundle:nil];
nextController.delegate = self;
[self addChildViewController:nextController];
[self.view addSubview:nextController.view];
[nextController didMoveToParentViewController:self];
temporaryController = nextController;
Removing:
[temporaryController didMoveToParentViewController:nil];
[temporaryController.view removeFromSuperview];
[temporaryController removeFromParentViewController];
temporaryController = nil;
Also if temporaryController is a strong property (or you've used an iVar), you should nil it out after removing it.
As the CAAnimation retains its delegate make you remove the animation and nil out the delegate.
-(void)didMoveToParentViewController:(UIViewController *)parentViewController
{
[super didMoveToParentViewController:parentViewController];
if (!parentViewController) {
CAAnimation *animation = [movingObject.layer animationForKey:#"animatePositionX"];
animation.delegate = nil;
[movingObject.layer removeAnimationForKey:#"animatePositionX"];
}
}
If you want to check your view controller is being deallocoated you should implement the dealloc method and place a breakpoint inside of it. I suggest a breakpoint over a NSLog as I don't know how much you already log out so it might get missed, with a breakpoint it is much clearly - actually stopping the program flow.
I have 2 ViewControllers that I use App delegate to switch them according to user interaction.
in AppDelegate.m I have:
- (void) switchViews
{
if (_viewController.view.superview == nil) {
[_window addSubview:_viewController.view];
[_window bringSubviewToFront:_viewController.view];
[viewController2.view removeFromSuperview];
} else
{
[_window addSubview:_viewController2.view];
[_window bringSubviewToFront:_viewController2.view];
[_viewController.view removeFromSuperview];
}
}
_viewController is for main view and _viewController2 is for glview(I am using isgl3d). The switch works but everytime I switch back to glview, I see duplicated view on top, which I suspect even main view is duplicated too.
Any idea how can I remove the view entirely so that I don't have this issue? Thanks!
You shouldn't be adding and removing the views like this, just change which controller is the root view controller of the window. Doing that make the new controller's view a subview of the window, and removes the old controller's view.
if ([self.window.rootViewController isEqual: _viewController]) {
self.window.rootViewController = viewController2;
}else{
self.window.rootViewController = viewController;
I found out how to do this after watching Stanford Coding Together:IOS.
Some critical info of VC that I am not aware of:
Everytime VC is instantiate, viewDidLoad is called once to setup all the important stuff like outlets and such. Then viewWillAppear and viewWillDisappear will be called for in between view swapping. Because it is called just a moment before view is shown to user, all the geometry setting like view orientation and size is set here.
so what I do is:
I addSubview in viewDidLoad, the do all the running setup in viewWillappear and viewWillDisappear.
one more note: view will remain there as long as the app still running.
anyway Thanks rdelmar for helping.
I am trying to get a popup effect and want to design the popup view in another view controller so i can use the xib to do it.
When i used the presentViewController or pushViewController and set the background to transparent, i end up seeing the Window's background color.
I tried this code to add subview to the navigation controller's view so that i can have the Info view cover the entire screen with a transparent background. I also have tab bar to cover up as well.
InfoVC *vc = [[InfoVC alloc] initWithNibName:#"InfoVC" bundle:nil];
[self.navigationController.view addSubview:vc.view];
My problem is inside my InfoVC when i try to dismiss it, the app will crash with some EXC_BAD_ACCESS message:
[self.view removeFromSuperview];
EDIT:
I found a way to stop it crashing but setting the InfoVC as a property in the MainVC. I think the reason for crash is when i call "self.view" in the action inside the InfoVC, it doesn't know that self is the InfoVC inside MainVC.
InfoVC *vc = [[InfoVC alloc] initWithNibName:#"InfoVC" bundle:nil];
[self.navigationController.view addSubview:vc.view];
No no no no. Never never do that.
There is an elaborate dance that you must traverse in order to put a view controller's view inside another view controller's view (or remove it afterwards) if it doesn't come with built-in facilities for doing this (the way a UISplitViewController does, or the way a navigation controller manages the views of the view controllers that are pushed and popped within it).
Read up on customer container controllers. One of the examples from my book is here:
https://github.com/mattneub/Programming-iOS-Book-Examples/blob/master/ch19p556containerController/p476containerController/ViewController.m
Shouldn't you be using the following to remove the view from its superview?
[vc.view removeFromSuperview];
You can never have a UIView remove it's subviews, the subviews themselves must remove themselves from it's superview. You can easily loop through subviews and have them removed like so
for (UIView *view in vc.view.subviews) {
[view removeFromSuperview];
}
Docs for reference:
http://developer.apple.com/library/ios/#documentation/uikit/reference/uiview_class/uiview/uiview.html
After a "modally" presented view controller has appeared the views under the now presented view controller will be removed; this saves memory, and eases rendering. In your case, though, you also end up seeing the window behind the "modally" presented view.
The natural, and seemingly logical, next step is to simply take one view controller's view and cram it into another. However, as you have discovered, this is problematic. With the newly inserted view safely retained by the view hierarchy it is safe, but the new view controller is not so lucky, it is quickly deallocated. So when this new view tries to contact its controller you will get an EXC_BAD_ACCESS and crash. One workaround, again as you have found, is to simply have the original view controller keep a strong reference to the new view controller. And this can work... badly. There's still a good chance you will get an UIViewControllerHierarchyInconsistencyException.
Of course if you simply want to add a small view you create in IB you don't need to use a view controller as the "File's Owner" and there are many examples of creating an instance of a view from a xib file.
The more interesting question here is, "How would/does apple do it?" Apple consistently says that a view controller is the correct controller for an encapsulated unit of work. For example, their TWTweetComposeViewController, you present it, and it seems to float. How?
The first way of accomplishing this that comes to my mind is to have a clear background that isn't clear. That is, create an image of the screen before the presented view controller appears and set that as the background before the presenting view is removed. So for example(Explanation to follow):
QuickSheetViewController.xib
QuickSheetViewController.h
#import <UIKit/UIKit.h>
#interface QuickSheetViewController : UIViewController
- (IBAction)dismissButtonPressed:(id)sender;
#end
QuickSheetViewController.m
#import "QuickSheetViewController.h"
#import <QuartzCore/QuartzCore.h>
#implementation QuickSheetViewController {
UIImage *_backgroundImage;
}
-(void)renderAndSaveBackgroundImageFromVC:(UIViewController *)vc{
UIGraphicsBeginImageContext(vc.view.bounds.size);
[vc.view.layer renderInContext:UIGraphicsGetCurrentContext()];
_backgroundImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
// save an image of the current view, and set our background to clear so we can see the slide-in.
[self renderAndSaveBackgroundImageFromVC:self.presentingViewController];
self.view.backgroundColor = [UIColor clearColor];
}
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
// Time to use our saved background image.
self.view.backgroundColor = [UIColor colorWithPatternImage:_backgroundImage];
}
-(void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
// Set our background to clear so we can see the slide-out.
self.view.backgroundColor = [UIColor clearColor];
}
- (IBAction)dismissButtonPressed:(id)sender {
[self dismissViewControllerAnimated:YES completion:nil];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end
The majority of this example hinges upon the renderAndSaveBackgroundImageFromVC: method. In which, we create a graphics context render the view we are about to cover into it, and then create a UIImage to later (in viewDidAppear) use as a background.
Now simply use it like:
QuickSheetViewController *newVC = [[QuickSheetViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController:newVC animated:YES completion:nil];
You will see through the background just long enough for the animation to happen, then we use our saved image to hide the removal of the presenting view.
My application starts off with nothing but a UIWindow. I programmatically add a view controller to self.window in application:didFinishLaunchingWithOptions:.
myViewController = [[UIViewController alloc] init:...];
...
[self.window addSubview:myViewController.view];
[self.window makeKeyAndVisible];
At the same time i kick off a background process:
[NSThread detachNewThreadSelector:#selector(startupOperations) toTarget:self withObject:nil];
The startupOperations look something like this:
NSAutoreleasePool *threadPool = [[NSAutoreleasePool alloc] init];
// Load data
...
// When your done, call method on the main thread
[self performSelectorOnMainThread:#selector(showMainViewController) withObject:nil waitUntilDone:false];
// Release autorelease pool
[threadPool release];
showMainViewController removes myViewController, creates a UITabBarController and sets it as the window's main view:
[self.myViewController.view removeFromSuperview];
self.myViewController = nil;
tabBarController = [[UITabBarController alloc] init];
...
[self.window addSubview:tabBarController.view];
[self.window makeKeyAndVisible];
Questions:
All the view controllers are returning YES for shouldAutorotateToInterfaceOrientation:. Rotation works fine for myViewController but as soon as the tabBarController is made visible, rotation stops working and interface appears in Portrait. What's the reason behind this behavior?
Also, in iOS 4.x, UIWindow has rootViewController property. What's the role of this property? The new templates use rootViewController instead of [self.window addSubview:...]. Why is that?
Pretty strange. I tried and simulate your "view flow" in a simple tab bar based project and autorotation effectively works after removing the initial controller and adding the tab bar controller's view as a subview.
The only condition I found where it did not work is when self.window did contain a second subview that I did not remove. Could you check at the moment when you execute
[self.window addSubview:tabBarController.view];
what is self.window.subview content?
If that does not help, could you share in your question how you initialize the UITabBarController and UITabBar?
As to your second question, as you say rootViewController is the root controller for all the views that belong to the window:
The root view controller provides the content view of the window. Assigning a view controller to this property (either programmatically or using Interface Builder) installs the view controller’s view as the content view of the window. If the window has an existing view hierarchy, the old views are removed before the new ones are installed.
(Source)
You can also use that, but take care of assigning it already in applicationDidFinishLaunching, otherwise, if you "manually" add a subview and later change this property, it will not remove the subview you explicitly added.
I'm pretty new to iOS development, and I'm trying to develop a simple app in which a button changes the subviews. I have a base RootViewController, which displays MiddleView correctly on init. MiddleView has a single button, labeled "First," which is connected (in Interface Builder) to RootViewController's -openFirstView.
Here's how MiddleView is displayed within RootViewController's -viewDidLoad
MiddleViewController *middleTemp = [[MiddleViewController alloc] initWithNibName:#"MiddleView" bundle:nil];
self.middle = middleTemp;
self.middle.rootViewController = self;
[self.view addSubview:middle.view];
[middleTemp release];
So I have the following ViewControllerss: MiddleViewController and FirstController which control MiddleView and FirstView respectively, and a RootViewController which switches between the two.
I've linked this by placing a RootViewController reference in MiddleViewController, and adding
self.middle.rootViewController = self;
to RootViewController's -viewDidLoad.
-(IBAction)openFirstView:(id)sender{
[middle.view removeFromSuperview];
[self.view addSubview:firstController.view];
}
Note: I've tried initializing firstController within -openFirstView, and when it initially didn't run, I moved the initialization to -viewDidLoad and have proven that it is initializing from the nib correctly by displaying FirstView directly in -viewDidLoad
Where firstController is loaded to a reference earlier in code. However, when I run the code and click the button, nothing in the view changes.
I've done some more diagnosing. I've found specifically that -ViewDidLoad in rootViewController is being called twice, once on the original load and once on the first click of the button, and I'm not sure exactly why.
It seems you haven't inialize your firstView in the below method
-(IBAction)openFirstView:(id)sender{
[middle.view removeFromSuperview];
//First initialize the firstController
[self.view addSubview:firstController.view];
}