Let me first say that I've searched Google and, although many have similar issues, I haven't seen anything with the following bizarre behavior and remedy.
I've created a UIViewController and associated nib with several IBOutlets. On trying to consume this nib from another class, I discovered that after instantiating it with initWithNibName:bundle:, the IBOutlets are still nil.
I confirmed that they are correctly wired up, and yes, they are being synthesized, but still nothing. While investigating further, I changed the initWithNibName method as follows:
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
UIView *view = self.view;
NSArray *subviews = self.view.subviews;
NSLog(#"Loaded view containing %d subviews.", [subviews count]);
}
return self;
}
Unbelievably, the addition of the three lines here, creating throwaway variables and logging, makes the IBOutlets wire up properly and work from the outside.
I have cleaned and rebuilt and restarted my machine, but still, if I remove these lines, it stops working. I am really baffled here and concerned that I have some kind of voodoo working that's going to break the moment I ship. Any ideas on what could be happening?
You misunderstand what initWithNibName:bundle: does, and when a UIViewController loads its nib.
The initWithNibName:bundle: method records the name of the nib to be loaded. It does not immediately load the nib.
The -[UIViewController view] method loads the nib on demand, by sending [self loadView] if necessary. The implementation of -[UIViewController view] is basically this:
- (UIView *)view {
if (_view == nil) {
[self loadView];
[self viewDidLoad];
}
return _view;
}
So if you call self.view in your initWithNibName:bundle: override, that will cause the view controller to load its nib.
However, it's generally inappropriate to call self.view from initWithNibName:bundle:. A view controller should be able to exist without its view hierarchy.
For example, suppose a user is running your app and navigates through several view controllers, which you implement by pushing the view controllers onto a navigation controller. Then the user switches to another app for a while. Now the system is running low on memory, so it kills background apps - including your app.
When the user launches your app again, your app (if it's well done) should try to restore the user's state. That means reloading the navigation controller with the stack of push view controllers. But only the top view controller's view is visible on screen. It would be a waste of time, memory, and battery to reload the views for all of the hidden view controllers immediately. That's why each view controller loads its nib on demand.
Related
After a viewcontroller has been presented modally, the initial preferredfocusedview is called. However, after we dismiss the viewcontroller and it has been dealloc. preferredfocusedview is not called after presenting the viewcontroller again. Running on tvOS 9.2.
Even adding the following did not help:
-(void) viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[self setNeedsFocusUpdate];
[self updateFocusIfNeeded];
}
Anyone know what's going on? Or if there's anyways to debug this?
Edit:
the way I am adding the viewcontroller:
viewController = [[UIViewController alloc] init];
[viewController addChildViewController:self];
[viewController.view addSubview:self.view];
[self didMoveToParentViewController:viewController];
If you are using a container view, having multiple ViewControllers or adding only one View Controller, the preferredFocusEnvironments method must be called from the rootView Controller indicating which View Controller to focus.
For eg.
View Controller A has a container View having ViewControllers B and ViewController C inside the Container.
View Controller A should have preferredFocusEnvironments returning which ViewController to focus.
This way, preferredFocusEnvironments on ViewController B or ViewController C will be called whenever the view becomes visible.
If the ViewController A doesn't have preferredFocusEnvironments, then it won't be called on the containerView ViewControllers.
Implementing custom focus behavior in tvOS 9 is disaster. Apple already mentioned that there is a limitation on redirecting focus specially when presenting/ dismissing a viewcontroller in WWDC.
tvOS10 will handle munch better with preferredFocusEnvironments.
https://developer.apple.com/videos/play/wwdc2016/215/
When I needed to fix this focus redirection issues in viewDidAppear in tvOS 9, I had exactly same issues. Sometimes it works, sometimes not. No clue what so ever. But after I put split second delay on setNeedsFocusUpdate / updateFocusIfNeeded in viewDidAppear it was way better in terms of consistency. preferredFocusedView get called all the time.
-(void) viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self setNeedsFocusUpdate];
[self updateFocusIfNeeded];
});
}
Do this in both presented and presenting view controllers, if you are manually changing focus. This is all from my observation and I don't think there is a proper way to achieve some focus behavior because tvOS API is kind of new and premature. Sorry about not being able to give you good explanation why this might work. Good luck.
Coming from an Android and Java background, I am relative new with Xcode Development.
I am using Xcode 5.0.2 and created my first IOS Application by selecting Create a New Xcode Project -> Single View Application. The initial project structure has been generated and I found that there is a Main_iphone.storyboard file which opens a UI Designer where I can drag and drop items to it. I selected UIScrollView and dragged it into the main window that has been generated.
Now in the Controller header file, I added #property (nonatomic, retain) IBOutlet UIScrollView *scrollView; so that i could access the scrollView from inside my controller code.
I wanted to add an item to the scrollView programatically so I created a template Custom View by adding new file -> Objective-C Class with XIB for User Interface, named it TSTFilesInfoController and designed the XIB by adding a View and a label inside the view. Same with the scrollView above, I created a property to expose the mainView in my controller class.
I hardcoded a loop of 10x inside the controller of the UIScrollView and inside the for loop I am instantiating TSTFilesInfoController and adding the view to the UIScrollView. But when i run the application, nothing is shown or added in the UIScrollView.
Heres the code for adding the CustomView:
- (void)viewDidLoad {
[super viewDidLoad];
for ( int i = 0; i < 10 ; i++) {
TSTFilesInfoController *info = [[TSTFilesInfoController alloc] init];
[self addChildViewController:info];
[self.scrollView addSubview:info.mainView];
NSLog(#"View has been added into the scrollView");
}
}
Can someone please tell me whats wrong with my codes and what would be the correct approach to achieve the output that i wanted? Thank you in advance for the help.
-- EDIT --
This code is auto-generated in TSTFilesInfoController.m
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
This is a misuse of a UIViewController subclass. Do not use a view controller just as a sort of fishing rod to hook a view that's inside a xib file. Simply load the xib file and grab the view yourself, and stuff it into your interface.
There are complex rules for how to put a view controller's view manually inside your interface, and in general it is something you should be reluctant to do. But making views come and go dynamically and directly is easy and common.
Let's suppose the .xib file is called TSTFilesInfo.xib and it has a top-level UIView subclass object, class MyView, which is the one you want. Then:
MyView* v = (MyView*)
([[UINib nibWithNibName:#"TSTFilesInfo" bundle:nil]
instantiateWithOwner:nil options:nil][0]);
This loads the nib once, instantiating its contents, and handing you a reference to that instance (the UIView in this case). Now plunk v into your interface. Keep that reference in an instance variable (probably weak, since it is retained by its superview) so that you can subsequently configure and communicate with any subviews of MyView to which you have created outlets.
NOTE: However, I must say from the example so far that it sounds to me like what you really want here is a UITableView, not a simple UIScrollView. It comes all set to do just the kind of thing you seem to up to here.
I'm new at objective-c so please bear with me. I have a class that returns a picture from a webcam and I am trying to display that to the screen. I subclassed NSViewController to get the image from the camera class and set it to an instance NSImageView and set the NSViewController's view to be the NSImageView. I have created a custom view in Interface Builder, dragged a NSViewController object into MainMenu.xib set it's class to be PhotoGrabberController, and control click-dragged from the custom view to the PhotoGrabberController to set it's outlet binding to be the view. (I really don't know how that works behind the scenes, it seems like magic to me). Nothing shows up on the screen and I've been playing around with this forever.
In PhotoGrabberController.h
#interface PhotoGrabberController : NSViewController {
PhotoGrabber * grabber;
NSImageView* iView;
}
#property (nonatomic, retain) NSImageView* iView;
In PhotoGrabberController.m
#implementation PhotoGrabberController
#synthesize iView,grabber;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
- (void) awakeFromNib
{
self = [super init];
if (self) {
NSRect rect = NSMakeRect(10, 10, 200, 100);
iView = [[NSImageView alloc] initWithFrame:rect];
[iView setImageScaling:NSScaleToFit];
[iView setImage:[NSImage imageNamed:#"picture.png"]];
grabber = [[PhotoGrabber alloc] init];
grabber.delegate = (id)self;
//[grabber grabPhoto]; (This usually sets iView but I removed it and manually set iView to be an image from file above for simplicity)
[self setView:iView];
}
}
I toyed around with putting a bunch of different things in the AppDelegate's applicationDidFinishLaunching but the way it's set up right now I think I shouldn't need to put anything in there.
Question
How do I get the main window to show the image?
Is it ok to use PhotoGrabberController.view instead of creating a view subclass?
What is wrong with my understanding of how things work here? I've spent a lot of time trying to figure this out and have gotten nowhere.
Can you direct me to a resource where I can fully understand how this works? I've found Apple documentation too detailed and thick. I just want to understand how windows, views, and view controllers are loaded and interact.
How do I get the main window to show the image?
That's a view's job.
As you already have a view, you just need to get it into the window. A window only holds one view directly, which is called its content view; most probably, you will want to add the view controller's view as a subview of the view that is already the content view, or as a subview of some other grandchild view.
Is it ok to use PhotoGrabberController.view instead of creating a view subclass?
These are orthogonal. The VC's view is an instance of a view class. Creating a class has nothing to do with using an instance.
I don't think creating a view subclass will help you here. You already have two working views: a plain NSView as the VC's immediate view, and a NSImageView within it. No subclass is necessary to add these to the view—with the image view within it—to the window.
What is wrong with my understanding of how things work here?
You've missed the entire concept of the view hierarchy, and the fact that such a hierarchy is how every window displays its content.
Also, you began your question with “I'm new at objective-c” (sic), but your question is about the Cocoa framework (specifically, the AppKit framework), not the Objective-C language.
Can you direct me to a resource where I can fully understand how this works?
The Window Programming Guide (particularly, “How Windows Work”) and the View Programming Guide (particularly, “Working with the View Hierarchy”).
I am trying to open a ViewController from within another ViewController if certain conditions are met. The code seems to run without error but the view is never shown. I am new to xcode 4 /ios 5 so I must be missing something.
Here is the code responsible for opening the second viewcontroller:
CreateUserViewController *createUserController = [[CreateUserViewController alloc] initWithNibName:#"CreateUserView" bundle:[NSBundle mainBundle] keyWrapper:keyChainWrapper];
[self presentViewController:createUserController animated:YES completion:nil];
In my project I have a xib called, "CreateUserView". I have added a view controller to this xib and assigned it to, "CreateUserViewController".
Also I noticed in the apple documentation that is shows setting the delegate of the viewcontroller to be presented. But it seems that no property called, "delegate" is on the viewcontroller object. Is this documentation old? This is the document I am trying to use (section 9-1):
View Controller Programming
Can someone give me a hint? Thanks..
edit Adding Custom Constructor
-(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil keyWrapper:(KeychainItemWrapper *)keyWrapper
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if(self){
[self setKeyChainWrapper:keyWrapper];
}
return self;
}
Regarding CreateUserView.xib: you don't want to put a CreateUserViewController object in the nib. You want to set the custom class of the File's Owner placeholder to CreateUserViewController. Then you need to connect the view outlet of File's Owner to the top-level view in the nib.
Regarding the delegate property: The UIViewController class doesn't have its own delegate property. The idea is that you add a delegate property to your subclass of UIViewController. The delegate provides a way for your presented view controller to pass custom information back to the presenting view controller.
Why would you want to do that? Let's consider the code you posted. I'll assume you have a UserListViewController that shows a list of User objects, and has a "Create new user" button. When the user touches the "Create new user" button, you create a CreateUserViewController and present it.
The user interacts with the CreateUserViewController to set the attributes of the new User object - name, rank, hairstyle, etc. Then he touches a "Done" button. Your CreateUserViewController creates the new User object and puts it in the database. Then it needs to dismiss itself, so the UserListViewController's list of User objects will appear again.
But you want the User list to include the newly created User object and you want to scroll the list so that the new User is on the screen. So you need a way to have your CreateUserViewController tell the UserListViewController about the newly created User object. This is where the delegate comes in.
You define a protocol like this:
#protocol CreateUserViewControllerDelegate
- (void)didCreateUser:(User *)user;
#end
and you give your CreateUserViewController a delegate property:
#interface CreateUserViewController
#property (weak, nonatomic) id<CreateUserViewControllerDelegate> delegate;
// ...
When your CreateUserViewController's "Done" button is touched, you notify your delegate of the new User:
- (IBAction)doneButtonWasTouched:(id)sender {
User *user = [self createUser];
[self.delegate didCreateUser:user];
[self dismissViewControllerAnimated:YES completion:nil];
}
In your UserListViewController, you adopt and implement the protocol:
#interface UserListViewController <CreateUserViewControllerDelegate, UITableViewDelegate, UITableViewDataSource>
// ...
#end
#implementation UserListViewController
- (void)didCreateUser:(User *)user {
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:[self.users count] inSection:0];
[self.users addObject:user];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation: UITableViewRowAnimationAutomatic];
[self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition: UITableViewScrollPositionNone animated:YES];
}
and when you need to present a CreateUserViewController, you set the new controller's delegate to the UserListViewController:
- (IBAction)createUserButtonWasTouched:(id)sender {
CreateUserViewController *createUserController = [[CreateUserViewController alloc] initWithNibName:#"CreateUserView" bundle:[NSBundle mainBundle] keyWrapper:keyChainWrapper];
createUserController.delegate = self;
[self presentViewController:createUserController animated:YES completion:nil];
}
In iOS5 the method for pushing new view controllers was really changed around quite a bit from iOS4 and Xcode 3. In summary, storyboards are now used to create your application view controller flow. Even though you may use standalone .xib files to build an application it is much less common in iOS5.
Anyway, the main method for pushing new view controllers onto the screen is done using segues. Check out this tutorial for an introduction: http://www.raywenderlich.com/5138/beginning-storyboards-in-ios-5-part-1
It does a good job on explaining how to create a storyboard and use segues. You can still present view controllers in code "the old way" but it is much much less common now with the introduction of these new technologies. There are also some absolutely awesome tutorials on iTunes U - search for CS193P. It's the Stanford Introductory class to Objective-C and programming for iOS. This should get you started and maybe help you think of a way to push your createUserController in a way more up to speed with iOS5.
UPDATE
I just wanted to add. If you configure your program to use storyboards and segues you can use the method performSegueWithIdentifier:sender: to perform the segue to your createUserController view if the proper conditions are met. See the Apple API for UIViewController for information on how to use this method.
I have a UIViewController subclass that contains an instance of UIImagePickerController. Let's call this controller CameraController. Among other things, the CameraController manages the UIImagePickerController instance's overlayView, and other views, buttons, labels etc. that are displayed when the UIImagePickerController, let's call this instance photoPicker, is displayed as the modal controller.
The photoPicker's camera overlay and the elemets that are part of the CameraController view hierarchy display and function as expected. The problem I'm having is that I cannot use UIViewController's default initializer to create the CameraController's view heirarchy.
I am initializing CameraController from within another UIViewController. Let's call this controller the WebViewController. When the user clicks on a button in a view managed by WebViewController, the launchCamera method is called. It currently looks like this:
- (void) launchCamera{
if (!cameraController) {
cameraController = [[CameraController alloc] init];
// cameraController = [[CameraController alloc] initWithNibName:#"CameraController"
// bundle:[NSBundle mainBundle]];
cameraController.delegate = self;
}
[self presentModalViewController:cameraController.photoPicker animated:NO];
}
I want to be able to create CameraController by calling initWithNibName:bundle: but it's not working
as I'll explain.
CameraController's init method looks like this:
- (id) init {
if (self == [super init]) {
// Create and configure the image picker here...
// Load the UI elements for the camera overlay.
nibContents = [[NSBundle mainBundle] loadNibNamed:#"CameraController" owner:self options:nil];
[nibContents retain];
photoPicker.cameraOverlayView = overlay;
// More initialization code here...
}
return self;
}
The only way I can get the elements to load from the CameraController.xib file is to call loadNibNamed:owner:options:. Otherwise the camera takes over but no overlay nor other view components are displayed. It appears that a side-effect of this problem is that none of the view management methods on CameraController are ever called, like viewDidLoad, viewDidAppear etc.
However, all outlets defined in the nib seem to be working. For example, when the camera loads a view is displayed with some instructions for the user. On this view is a button to dismiss it. The button is declared in CameraController along with the method that is called that dismisses this instructions view. It is all wired together through the nib and works great. Furthermore, the button to take a picture is on the view that servers as photoPicker's overlay. This button and the method that is called when it's pressed is managed by CameraController and all wired up in the nib. It works fine too.
So what am I missing? Why can't I use UIViewController's default initializer to create the CameraController instance. And, why are none of CameraController's view mangement methods ever called.
Thanks.
Your problem is easy but need some steps.
Well... First, if overlay is an IBOutlet, it can not be loaded at init time. So move picker and co in viewDidLoad. Place also here all other items that your say that they are not loaded. They should be loaded there (viewDIDLoad). Check that outlets are connected.
Second, call
cameraController = [[CameraController alloc] initWithNibName:#"CameraController"
bundle:nil];
and ensure that CameraController contains (just) a view, and CameraController inherits UIViewController. Check also file's owner.
And at some time, you may consider that calling :
[self presentModalViewController:cameraController.photoPicker animated:NO];
does not make the CameraController control your picker. Does that make sense to you ?
What does that do regarding your problem ?
It seems you are confusing some things. I try to explain in another way :
The one that controls the picker is the one that is its delegate. Your may consider creating in a MAIN view.
The controller of the overlay (added as subview) is the one that own its view in File's Owner. That may be created from the MAIN view, adding its view as subview of the controller. Basically, it is loaded just to get the overlay, but viewDidLoad, ... won't be called.
That's all and I belive those steps are not ok in your code.
That should give something like :
MainController
Loadcamera {
self.picker = [UIImagePicker alloc] init.....];
self.picker.delegate = self;
SecondController* scnd = [[SecondController alloc] initWithNibName:#"SecondController" bundle:nil];
[self.picker addOverlay:scnd.view];
[self presentModalViewController:self.picker animated:NO];
}
/// And here manage your picker delegate methods
SecondController
// Here manage your IBActions and whatever you want for the overlay