I have a UIViewController with a custom init method that looks like this:
- (id)initWithFrame:(CGRect)frame_ customObject:(CustomObject *)object_ {
if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
self = [super initWithNibName:#"ArtistViewController_iPad" bundle:nil];
} else {
self = [super initWithNibName:#"ArtistViewController" bundle:nil];
}
[self.view setFrame:frame_];
self.customObject = object_;
return self;
}
But when [self.view setFrame:frame_]; is called, it crashes with this in the log:
(null)
libc++abi.dylib: terminate called throwing an exception
This is how I allocate the UIViewController from another UIViewController:
CGRect frame = self.view.frame;
artistViewController = [[ArtistViewController alloc] initWithFrame:frame customObject:anObject];
the frame exists. self exists from [super initWithNibName:bundle];
But self.view seems to not exist. The nib files exist and have their view outlet hooked up.
Why does this happen?
You should not access the view from within the initializer. There are several more appropriate places to do this work, depending on what you really want to accomplish.
Read the view controller lifecycle to understand where you may want to place your modifications.
http://developer.apple.com/library/ios/#featuredarticles/ViewControllerPGforiPhoneOS/ViewLoadingandUnloading/ViewLoadingandUnloading.html#//apple_ref/doc/uid/TP40007457-CH10-SW1
Related
Where should I initialize a UITablewView as a subview, in - (id)initWithFrame:(CGRect)frame, in viewdidload or loadView? Which is the better approach? Where should I make the frame (I mean which is more effective)?
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
self.backgroundColor = kViewBackgroundColor;
_tableView = [[UITableView alloc] initWithFrame:CGRectZero style:UITableViewStyleGrouped];
_tableView.backgroundView = nil;
_tableView.backgroundColor = [UIColor clearColor];
_tableView.bounces = NO;
[self addSubview:_tableView];
}
return self;
}
On my projects I usually create a baseViewController with a custom initialiser like this:
- (id)init{
self = [self initWithNibName:NSStringFromClass([self class]) bundle:[NSBundle mainBundle]];
if (self) {
//You should create the tableView and other properties here
//and add as subviews inside viewDidLoad
_tableView = [[UITableView alloc]initWithFrame:CGRectMake(0,0,100,100)];
}
return self;
}
and I always create my view controller by using this init method, because I don't think the other vc's need to know the name of the nib file. If I were you I would create subviews inside init method, add as subviews inside viewDidLoad or viewWillAppear and finally releasing them inside dealloc if you are not using ARC.
Generally this depends on your requirement that if you are having custom view called with a tableview as subview then loadview with the initwithframe method will be better and while you want to initialize it from viewcontroller then viewdidload is better. I think you should bifurcate your requirement. Hope this helps.
Since you are initializing table view with zero frame it wont be visible even if you added that
you can try this
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
self.backgroundColor = kViewBackgroundColor;
UITableView *_tableView = [[UITableView alloc] initWithFrame:self.bounds style:UITableViewStyleGrouped];
_tableView.backgroundView = nil;
_tableView.backgroundColor = [UIColor clearColor];
_tableView.bounces = NO;
[_tableView setAutoresizingMask:UIViewAutoresizingFlexibleHeight|UIViewAutoresizingFlexibleWidth]
[self addSubview:_tableView];
}
return self;
}
If you'd like to create subviews programmatically based on superview metrics (frame or bounds), you should do it in viewDidLoad, because if you do in in initializer, metrics of self.view will not be avaliable, and you subviews will be created with zero frame and will not be visible (as Johnykutty) mentioned above.
But that does not seem to be a good practice in case your subview initialization routines require heavy operations.
Offtopic: I've been codin' for a looong time trying to do everything programmatically, never using xibs, etc. Well, if you ask me now, xibs really save your time and make life easier. Consider using interface builder for layout\autolayout, colors\borders etc stuff.
point 1. in delegate:
self.friendListVC = [[FriendListVC alloc] init];
point 2.
in FriendCollectionVC.mm:
- (void)viewDidLoad
{
[super viewDidLoad];
FriendCollectionVC *friendCollectionVC = [[FriendCollectionVC alloc] init];
[self.view addSubview:friendCollectionVC.view];
}
point 3. run:
use lldb:
po [self collectionView].delegate
p [self collectionView]
result:
[no Objective-C description available]
(PSTCollectionView *) $6 = 0x212bc400
point 4. continue run.
use lldb:
po [self collectionView].delegate
p [self collectionView]
result:
2013-11-30 00:15:25.637 App[45683:70b] *** -[FriendCollectionVC respondsToSelector:]: message sent to deallocated instance 0x67259eb0
[no Objective-C description available]
(PSTCollectionView *) $6 = 0x6785eca0
and use lldb at the same time:
po ((MyAppDelegate *)[[UIApplication sharedApplication] delegate]).friendListVC.view
<UIView: 0x6656efa0; frame = (0 0; 945 748); autoresize = W+H; layer = <CALayer: 0x665d0fd0>>
point 5. Question:
Why the friendCollectionVC inside FriendListVC was released?
The AppDelegate and AppDelegate.friendListVC and AppDelegate.friendListVC.view are all available.
The friendListVC.view contains subview friendCollectionVC.view. - see code 2.
And the project is using ARC.
You are not keeping any strong pointer to friendCollectionVC, since you create it as a local variable. Adding its view as a subview doesn't do anything to change that fact. In any case, it's not a good idea to just add one controller's view as a subview of another controller's view. When you add friendCollectionVC's view as a subview of FriendListVC's view, you should make friendCollectionVC a child view controller of FriendListVC, using the custom container controller api. If you do that, FriendListVC will have a strong pointer (in its childViewControllers array) to friendCollectionVC.
- (void)viewDidLoad {
[super viewDidLoad];
FriendCollectionVC *friendCollectionVC = [[FriendCollectionVC alloc] init];
[self addChildViewController:friendCollectionVC];
[friendCollectionVC didMoveToParentViewController:self];
[self.view addSubview:friendCollectionVC.view];
}
In my app I habe a view controller that calls several views. All these views are UIViews. That works fine, but not in every case. One of the views that are called has some labels, textfields and two UITextViews. Everything is shown correctly but the UITextViews. The view is called in that way:
[[self view] addSubview:tasteView];
//tasteView = [[TasteView alloc] init];
[self setCurrentView:tasteView];
I call the init method of the view to display the UITextViews:
EDIT: After a comment of Phillip Mills this was slightly changed! Init isn't called anymore.
- (id)init
{
if (self)
{
[tv1 setNeedsDisplay];
CGRect frame = tv1.frame;
frame.size.height += 1;
tv1.frame = frame;
}
return self;
}
As I saw that setNeedsDisplay had no effect, I changed the size of the corresponsing frame to force a redraw. Unfortunately that had no effect, too.
Btw, the view is initially loaded in the viewDidLoad of the view controller:
- (void)viewDidLoad
{
[super viewDidLoad];
[self setCurrentView:placeholder];
[self configureView];
wineryView = [self loadWineryView];
wineView = [self loadWineView];
tasteView = [self loadTasteView];
}
A method for loading the views looks like this:
- (UIView *) loadTasteView
{
NSArray *nibViews = [[NSBundle mainBundle] loadNibNamed:#"TasteView" owner:self options:nil];
UIView *tView;
for (id view in nibViews)
{
if ([view isKindOfClass:[TasteView class]])
{
tView = (TasteView*) view;
}
}
return tView;
}
I do not know why those UITextViews are not shown. Did I forget something? To show really everything, here are the connections that I made in InterfaceBuilder:
Does anyone know what I did wrong and can help me?
I think your initial code should be like this :
tasteView = [[TasteView alloc] init];
[[self view] addSubview:tasteView];
[self setCurrentView:tasteView];
addSubView after it is allocated
Hope it helps you
If you are creating the view in code (your first sample), alloc and init the view before trying to add it as a subview.
If you're loading it from another nib (last code section), you still need to add it to the view hierarchy.
In post Using initWithNibName changes absolutely nothing, he shows two uses of the same View Nib definition, in the first case, he simply calls alloc/init and the second, he specifies initWithNibName.
So, while this always works:
MyViewController *vctrlr = [[MyViewController alloc] initWithNibName:#"MyViewController" bundle:nil];
[self.navigationController pushViewController:vctrlr animated:YES];
[vctrlr release];
The following works for all the View Controllers I've inherited, but not mine!
TheirViewController *vctrlr = [[TheirViewController alloc] init];
[self.navigationController pushViewController:vctrlr animated:YES];
[vctrlr release];
New to iOS programming, I inherited some code. All the View Controllers' views are defined in IB, but there was inconsistent allocation/init creation of those view controllers. I created a new View Controller and XIB, but it does not work unless I use initWithNibName (it crashes when I push the view controller onto the Nav Controller). I cannot tell how my view controller is different than the others... any hints? I was able to delete the initNibName usage for all the other view controllers in the app except mine.
You can pass any string name to initWithNibName:. You are not just restricted to calling initWithNibName:#"MyClassName" when your class is called MyClassName. It could be initWithNibName:#"MyClassNameAlternateLayout".
This becomes useful if you need to load a different nib depending on what the app needs to do. While I try to have one nib per view controller per device category (iPhone or iPad) whenever possible to make development and maintenance simpler, I could understand if a developer would want to provide a different layout or different functionality at times.
Another important point is that initWithNibName:bundle: is the designated initializer for UIViewController. When you call -[[UIViewController alloc] init], then initWithNibName:bundle: is called behind the scenes. You can verify this with a symbolic breakpoint. In other words, if you simply want the default behavior, it is expected that you can call -[[UIViewController alloc] init] and the designated initializer will be called implicitly.
If, however, you are calling -[[UIViewController alloc] init] and not getting the expected behavior, it's likely that your UIViewController subclass has implemented - (id)init incorrectly. The implementation should look like one of these two examples:
- (id)init
{
self = [super init];
if (self) {
// custom initialization
}
return self;
}
or
- (id)init
{
NSString *aNibName = #"WhateverYouWant";
NSBundle *aBundle = [NSBundle mainBundle]; // or whatever bundle you want
self = [self initWithNibName:aNibName bundle:aBundle];
if (self) {
// custom initialization
}
return self;
}
If you want to work following code:
MyViewController *vctrlr = [[MyViewController alloc] inil];
[self.navigationController pushViewController:vctrlr animated:YES];
Then you should implement following both methods in MyViewController:
- (id)init
{
self = [super initWithNibName:#"MyViewController" bundle:nil];
if (self != nil)
{
// Do initialization if needed
}
return self;
}
- (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)bundle
{
NSAssert(NO, #"Init with nib");
return nil;
}
I can't figure out what the problem is here. I have a very simple UIViewController with a very simple viewDidLoad method:
-(void)viewDidLoad {
NSLog(#"making game view");
GameView *v = [[GameView alloc] initWithFrame:CGRectMake(0,0,320,460)];
[self.view addSubview:v];
[super viewDidLoad];
}
And my GameView is initialized as follows:
#interface GameView : UIView {
and it simply has a new drawRect method:
- (void)drawRect:(CGRect)rect
{
[super drawRect:rect];
NSLog(#"drawing");
}
In my console, I see "making game view" being printed, but "drawing" never is printed. Why? Why isn't my drawRect method in my custom UIView being called. I'm literally just trying to draw a circle on the screen.
Have you tried specifying the frame in the initialization of the view? Because you are creating a custom UIView, you need to specify the frame for the view before the drawing method is called.
Try changing your viewDidLoad to the following:
NSLog(#"making game view");
GameView *v = [[GameView alloc] initWithFrame:CGRectMake(0,0,320,460)];
if (v == nil)
NSLog(#"was not allocated and/or initialized");
[self.view addSubview:v];
if (v.superview == nil)
NSLog(#"was not added to view");
[super viewDidLoad];
let me know what you get.
Check if your view is being displayed. If a view is not currently on screen, drawRect will not be getting called even if you add the view to its superview. A possibility is that your view is blocked by the some other view.
And as far as I know, you don't need to write [super drawRect];
Note that even if viewDidLoad is called on a view controller it doesn't necessarily indicate the view controller's view is displayed on screen. Example: Assume a view controller A has an ivar where a view controller B is stored and view controller A's view is currently displayed. Also assume B is alloced and inited. Now if some method in A causes B's view to be accessed viewDidLoad in B will be called as a result regardless whether it's displayed.
If you're using a CocoaTouch lib or file you may need to override the initWithCoder method instead of viewDidLoad.
Objective-C:
- (instancetype)initWithCoder:(NSCoder *)coder
{
self = [super initWithCoder:coder];
if (self) {
//Do Stuff Here
}
return self;
}
I had a view that was offscreen, that I would load onscreen and then redraw. However, while cleaning up auto-layout constraints in XCode, it decided my offscreen view should have a frame (0,0,0,0) (x,y,w,h). And with a (0,0) size, the view would never load.
Make sure your NSView has a nonzero frame size, or else drawRect will not be called.