This is an iPad app. You press one of two buttons and it presents a modal view controller containing a webview which will display a PDF. I created the UIViewController class containing the webview, and I want to use 1 of 2 initializers depending on which button the user pushes. When I initialize the object I want to set which PDF is displayed. The modal view is coming up but it is blank(No PDF displayed). However, when I use this same code within -(void)viewDidLoad{} it does work. Why is this? Thanks!
- (id)initAsPi{
NSLog(#"initAsPi Called");
[super init];
NSString *urlAddress = [[NSBundle mainBundle] pathForResource:#"PiPdf" ofType:#"pdf"];
NSURL *url = [NSURL fileURLWithPath:urlAddress];
NSURLRequest *urlRequestObj = [NSURLRequest requestWithURL:url];
[prescribingInfoWebView loadRequest:urlRequestObj];
return self;
}
Initialization
Your initialization method is wrong. Read Implementing an Initializer - Handling Initialization Failure at ...
http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/ObjectiveC/Articles/ocAllocInit.html%23//apple_ref/doc/uid/TP30001163-CH22-105377
It should look like ...
- (id)initAsPi {
self = [super init];
if ( self ) {
// Your initialization code
}
return self;
}
Why it does work in viewDidLoad and not in initAsPi?
prescribingInfoWebView is nil unless you're doing something obscure elsewhere.
You're probably creating prescribingInfoWebView in loadView method or it is automatically initialized during view load if you're loading your view from XIB.
When the init method of a view controller is executed, it has not yet loaded its view. So prescribingInfoWebView is probably nil at this point (you should check with the debugger) and so the message you are trying to send to it has no effect.
UIViewControllers load their interfaces lazily. This means any UI properties set up in Interface Builder or in -loadView will be nil until some request for the view causes it to load. In your initializer, this is almost certainly the problem.
Related
I have a strange problem and I have no idea how to solve it. I have a root viewcontroller. Via button you can switch to the child viewcontroller. In the child view controller I open a link like this as a request to the webview:
myURL = [NSURL URLWithString:#"http://m.imdb.com/video/imdb/vi2284695065/"];
NSURLRequest *myRequest = [NSURLRequest requestWithURL:myURL];
[myWebView loadRequest:myRequest];
the video on the page is autoplaying and switching to fullscreen mode. In exactly this moment I get a log message which indicates that the viewdidload method on my rootviewcontroller is called. Which eventually makes my code not working anymore. But why? Its not the viewdidload of the current viewcontroller its the one of the rootviewcontroller?! I don´t know what kind of code I should provide actually...
Edit
I switch to viewcontroller like this:
UIViewController *NVC = [self.storyboard instantiateViewControllerWithIdentifier:#"child"];
[self presentViewController:NVC animated:NO completion:nil];
The rootviewcontroller does not get a received memory warning.
I have two init functions in my UIViewController subclass:
- (id)init
{
self = [super init];
if (self)
{
// Custom stuff
return self;
}
return nil;
}
and
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName: nibNameOrNil
bundle: nibBundleOrNil];
if (self)
{
// Custom stuff
}
return self;
}
I put the init function in to avoid the call to the initWithNibName:bundle: method. I am trying to experiment with taking the xib file out. Unfortunately, calling this init [[Myclass alloc] init] calls initWithNibName:bundle: through the call to [super init].
First, where in the documentation should I be reading so that I would have expected the call to the parent init method to call my own initWithNibName:bundle: method?
Second, how is this a good design choice on Apple's part. I am not seeing why this is desirable behavior? (It may be that I am just not getting the big picture here so please feel free to clue me in.)
Third, how do I get around it best. Do I just take the initWithNibName:bundle: out of my code? Is there never a case where I would like the option of using either a xib or a manual instantiation of the class.
Usually I have to initialise my view controllers with managed object context. I implement simple -(id)initWithContext: method in which I call super's initWithNibName:bundle: method. This way I can define my own xib name.
Not sure about the first part of you question (the reading thing, that is), but Apple's class templates for VC's show that they have their own initWithNibName:bundle method which calls on super with same parameters as they are given. Hence from your situation I'd say that exactly this is designated initialiser and it's not "safe" to call simple init method on super as it will invoke initWithNibName:bundle. I believe UIViewController's init looks like this:
- (id)init
{
self = [self initWithNibName:nibNameDerivedFromClass bundle:probablyNilOrMainBundle];
if (!self) return nil;
// some extra initialization
return self;
}
Since the super class doesn't have initWithNibName:bundle it has to call method on itself making it the designated initialiser. Since you have overridden it, ObjC's runtime replaces self in that method with your class.
If you want to exclude Interface Builder from the creation of your UIViewController's GUI, you have to override loadView and create the view yourself. Don't implement initWithNibName:bundle:.
- (void)loadView {
// Init a view. The frame will be automatically set by the view controller.
UIView *view = [[UIView alloc] initWithFrame:CGRectZero];
// Add additional views (buttons, sliders etc.) to your view here.
// Set the view controller's view to the new view.
self.view = view.
}
First, where in the documentation should I be reading so that I would
have expected the call to the parent init class to call my own
initWithNibName:bundle: method?
You don't, it's a design thing. init is not the base initialization method for all classes
Second, how is this a good design choice on Apple's part. I am not
seeing why this is desirable behavior? (It may be that I am just not
getting the big picture here so please feel free to clue me in.)
When init calls that, it sends nil name and bundle, and it defaults to an empty xib file. There's always a xib file, yours or not.
Third, how do I get around it best. Do I just take the
initWithNibName:bundle: out of my code? Is there never a case where I
would like the option of using either a xib or a manual instantiation
of the class.
You don't. You don't really need to have that code there if you are just calling super, merely forwarding a method.
You can customize your view and add subviews in the viewDidLoad method. In this method you can check whether the class was created using init or using initWithNibName:bundle: by examining property nibName. When using init, nibName will be nil.
- (void)viewDidLoad
{
[super viewDidLoad];
if (!self.nibName) {
// View was not loaded from nib - setup view
}
}
I want to be able to use a blue object box to delegate control over an NSOutlineView. The blue object box would be hooked up to my primary controller, so it'd just be a data source and control the content of the NSOutlineView.
The problem I'm having is that I have no control over the Channel Data Source. I'm simply calling a declared method with some test NSLog inside of it, and it doesn't get called. The outlet doesn't get instantiated.
Here's the connections of the blue object box (ChannelDataSource)
Here's the connections of File's Owner for my primary controller.
So you see, I want to do something like [dataSource callMyMethod]; with the final aim that I have control over the contents for the NSOutlineView.
Any ideas?
EDIT
The application is structured whereby my primarily app delegate looks like this:
#implementation MyAppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// Insert code here to initialize your application
controller = [[MainController alloc] init];
[controller showWindow];
}
#end
Then in the MainController I have something along the following lines:
#implementation MainController
-(id)init {
self = [super init];
if (self) {
// loads of random stuff
[dataSource myMethod];
}
return self;
}
So "Channel Data Source" blue object box is dataSource. At this point in the application life cycle, it's null, which isn't what I was expecting. At the same time, it's still a bit of black magic to me. If you have a blue object box, at what point is it instantiated? Obviously this isn't hooked up correctly though.
EDIT EDIT
Further to my points above, and trying to fix the problem, is this actually a good way to go about it? I'm looking at this thinking it's not meeting a decent MVC architecture, because ultimately the blue object box's owning class is storing and managing the data. Is there a better way to go about managing what's in your NSOutlineView?
EDIT EDIT EDIT
So I have my app delegate, which is strangely a class all by itself that instantiates the main controller. Don't ask me why I did this, it was very early code. So my app delegate (root entry point) has this:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// Insert code here to initialize your application
controller = [[MyController alloc] initWithWindowNibName:#"MainWindow"];
[controller showWindow:nil]; // this doesn't open the window
[controller loadWindow]; // this does open the window
}
And the declaration of the controller:
#interface MyController : NSWindowController
Which contains the following method declaration in it:
-(void)windowDidLoad {
[dataSource insertChannel:#"test" forServer:#"test2"];
}
I have a breakpoint in windowDidLoad and it definitely doesn't get called.
Ideas?
There's still a few things you didn't clarify, but I can do some guessing. First, I'm assuming that MainController is a subclass of NSWindowController. If so, you should be using initWithWindowNibName: instead of just init, otherwise how would the controller know what window to show when you address showWindow: to it? Second, even if you do that, and change your init method to initWithWindowNibNamed:, what your wrote won't work, because the init is too early in the process to see your outlet, datasource. If you just log dataSource it will come up null. A better place to put that code would be in windowDidLoad, as everything will have been set up by then (this will be called after showWindow:). So, in my little test project, this is what I did.
In the app delegate:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
self.cont = [[Controller alloc] initWithWindowNibName:#"Window"];
[self.cont showWindow:nil];
}
In the Controller.M I have this:
- (void)windowDidLoad {
NSLog(#"%#",self.dataSource);
[self.dataSource testMethod];
}
In IB, in the Window.xib file, I set the class of the file's owner to Controller, and the class of the blue cube to ChannelDataSource. EVerything was hooked up the same way you showed in your post.
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
I have a modal view controller that I am trying to present a web view in it. Tthe first time it appears, it shows up as blank. When I close it out and click it again, however, it displays fine. I'm thinking it may be an issue with the loading of the webView, but I've tried displaying it only when the webView finishes loading, but it never gets called then.
NSURL* newURL = [[NSURL alloc] initFileURLWithPath: fileString];
NSURLRequest *newURLRequest = [[NSURLRequest alloc] initWithURL: newURL];
[webViewController.webView loadRequest: newURLRequest];
[newURL release];
[newURLRequest release];
webViewController.modalPresentationStyle=UIModalPresentationPageSheet;
[self presentModalViewController:webViewController animated:YES];
The webView control won't be accessible the first time until the first present call causes controls to be loaded and initialized. Before the first present, webViewController.webView will be nil and so calling loadRequest on it will do nothing.
You could move the loadRequest call after the presentModalViewController call.
But instead of accessing controls in view controller's views directly, it'd be better to declare the url string as a NSString property (called say urlString) in WebViewController and set it to fileString before the presentModalViewController call (and don't create the NSURL, etc there):
webViewController.urlString = fileString;
[self presentModalViewController:webViewController animated:YES];
Finally, in WebViewController, in viewWillAppear: or viewDidAppear:, create the NSURL (using urlString), create the NSURLRequest, and call loadRequest.