Is there an easy way to know when all the subivews have loaded?
Right now I'm doing:
if([[self subviews] count] == 10) {
//do stuff
}
If there isn't an event/method for this, is there at least a way to dynamically know what the child count is GOING to be?
edit
I re-read this just now and realize it's a bit asinine. Let me clarify:
I'm loading this UIView from a XIB file and I wanted to know when the NIB has officially loaded (with all of it's children). So I dare say the correct answer would be awakeFromNib
If you're calling this from a viewController, just use
-(void)viewDidLoad;
Which is called after the view and all its subviews are loaded. If you're doing it from one of the views inside the nib, use:
-(void)awakeFromNib;
Which is called after the view's subviews have been loaded.
If you are adding subviews programmatically (e.g. [myView addSubview:anotherView]), then of course there is no way to know; the program could add more subviews at any time, if you write it that way.
If you are loading the view from a nib, you are probably looking for the awakeFromNib method. From the NSObject UIKit Additions Reference:
The nib-loading infrastructure sends an awakeFromNib message to each object recreated from a nib archive, but only after all the objects in the archive have been loaded and initialized. When an object receives an awakeFromNib message, it is guaranteed to have all its outlet and action connections already established.
Related
I have created a custom view (Quantity View) with nib file in Swift. I have created some IBOutlets & IBActions (for buttons, labels etc.) in my custom view.
I tried to use this custom view (Quantity View) by assigning class name to a UIView in my storyboard.
It's showing me all the IBOutlets & IBActions in the Connections Inspector, as shown in this screenshot: .
I just want to show only delegate for the Custom view.
Possible Answer:
I thought I can use the -viewWithTag to get the views instead of Outlets.
But, I want to know if it's possible with having Outlets also or if there is much better way to do this?
What are the other possible ways (optimum) to handle this situation?
You can also consider the following solution:
You can take the subviews of your QuantityViews(custom view) and you can identify the specific views by its frame origin.
Note : you should know the customview subviews frame
Its not possible to hide IBOutlets from storyboard if you declare the class members as IBs (IBOutlets or IBActions).
The IBOutlets or the IBActions are just indicators to the interface builder so that it can show the names on it when you try to bind them it actually calls the setValue: forKey: method to set the view's reference to the IBOutlet property.
Now if you try to access an subview from the file's owner class without any IBoutlets you need to have a pointer to point it, so for that either you can get the reference using ObjectID which is assigned to the subview by the interface builder or you can get it using the viewWithTag: method.
The ObjectID you need to find all time when you add or replace a subview from the view, so better and convenient approach is to use tag property of UIView class.
So my conclusion to this problem is to access the views using the viewWithTag method you mentioned earlier.
I think your way is correct. But sometimes Xcode doesn't work correctly.
The following makes the IBOutlets and IBActions reappear and work properly:
Clean project your project in Xcode.
Quit Xcode completely.
Delete all contents of ~/Library/Developer/Xcode/DerivedData/.
Restart MacOS just in case.
I hope you will resolve that :)
I do a lot of animations with UIKit and I frequently store any animated view's initial frames in viewDidLoad to always have a reference to the frame as it appears in a xib.
This is kind of smelly and seems like the kind of thing that would be automated, but I can't seem to find any info on this. Is there a property on UIView that stores initial xib frame sizes? Or maybe a UIKit utility method that scans the xml of a xib for it's attribute values by name?
So while I could not find any way to access an interface builder file's initial attributes (unless you count writing an IB XML parser a way), I found a brilliant alternative from Do I need to set heightForRowAtIndexPath if I am using a custom UITableViewCell?. Instead of accessing some constant values from an object itself (I was hoping for a self.attribute.nib.value), you can make two outlets per IB object- one for manipulating, and one for a prototype- which will hold all the original values of the xib.
To makes things simple, just create an(other) outlet for your nib and override its getter.
For example, if we have a LargeCell.xib, we would create an outlet for largeCell and another for largeCellPrototype.
Then we would make a lazy accessor for this prototype to ensure the prototype is not nil and only loaded once.
- (LargeCell*)largeCellPrototype
{
if (!_largeCellPrototype)
{
[NSBundle mainBundle] loadNibNamed:NSStringFromClass([LargeCell class]) // Presuming you don't name files with reckless abandon
owner:self
options:nil];
}
}
now getting the initial values is as simple as
CGFloat initialViewHeight = self.largeCellPrototype.frame.size.height;
If I want to initialize views programmatically, where in the viewcontroller lifecycle should this happen?
The initial intuition is loadView. However, here, we don't yet have the frame of the view itself (necessary for calculating the sizes/positions of the views). Ditto for viewDidLoad.
Next intuition is viewWillAppear- here we DO (finally) have a guarantee of the frame of the view. However, this has potential to be called many times throughout the vc lifecycle. Ditto for viewDidAppear, etc...
Finally, I found viewWillLayoutSubviews. This works for the initialization of most static layouts- however, whenever any view moves this gets called again (same problem as viewWillAppear).
I've seen recommendations to init the views in loadView and set their frames in viewWillLayoutSubviews (since setting frames should be idempotent, who cares if it gets called a couple times). But then why does apple so strongly encourage initWithFrame: as the standard initialization method of UIViews (https://developer.apple.com/library/ios/documentation/windowsviews/conceptual/viewpg_iphoneos/CreatingViews/CreatingViews.html)?
Would it be crazy to subclass all my UIViewControllers to have an initWithViewFrame: method? That way I can pass in a frame, manually set it immediately in loadView and be done with it? Or is it better to have a viewHasBeenFormatted flag in viewWillAppear that, if not set, calls the formatting of views and then sets it?
Or is this just apple's way of saying "use interface builder or you're screwed"?
Any help is appreciated!
edit- accidentally wrote loadView where I meant viewWillAppear (in final paragraph)
update- I guess I've come to terms with the fact that there is no place where
The frame is confidently known
The code will only be run once (on setup)
Looks like you're expected to initWithFrame: all your views in viewDidLoad (but then I guess the contents of that view shouldn't treat that frame as even remotely final? because how could it be when it was derived on an assumption? ugh...). Then re-set their frames in layoutSubviews. And make sure to manually handle the differences between initial layout and layout as a result of a moved view there... Man I feel like I've GOT to be missing something... (lol denial...)
I guess that, OR submit and use IB.
update2- viewWillLayoutSubviews WILL get called when one of its subviews is resized. So it is still disqualified as it fails property 2 of the required characteristics that I'm looking for. :(
If you're doing layout with IB, it's fine to do additional view initialization in viewDidLoad (for example, if you need to do stuff that IB doesn't handle well, or if you have UIView subclasses with properties not supported by IB). Alternatively, if you're not using IB, the documentation says you should use loadView to manually initialize your view hierarchy.
You're right, though, that you can't rely on the frame being accurate at that point. So you can accomplish layout via each view's autoResizingMask property, layout constraints (if you're iOS 6 and later), and/or overriding layoutSubviews.
My usual approach is to do layout to some degree in IB, then do anything else I need to (nontrivial layout, custom classes, etc) in viewDidLoad. Then, if I have layout to figure out that autoResizingMask doesn't cover (I'm supporting down to iOS 5), I override viewWillAppear (or layoutSubviews if I'm subclassing UIView) and do some pixel math. I've got a category on UIView to help with this that has things like:
-(void)centerSubviewHorizontally:(UIView *)view pixelsFromTop:(float)pixels;
-(void)centerSubviewHorizontally:(UIView *)view pixelsBelow:(float)pixels siblingView:(UIView *)sibling;
View controllers should not have initWithFrame: methods. What I do in all of my code (I never use IB) is to let the default loadView do its own thing. I create and setup all subviews in viewDidLoad. At this point the view controller's frame has at least a sane value. All subviews can be created with their own sane frames based on the initial size of the view controller's view. With proper autoresizingMask values this may be all you need.
If you need more specific subview layout, put the appropriate layout code in the viewWillLayoutSubviews method. This will deal with any view controller view frame changes including rotation, in-call status bars, etc.
If you don't use interface builder you should override loadView and initialize the views there. If you use autolayout you can also add your constraints there. If you don't use autolayout you can override the layoutSubviews method of your views to adjust the frames.
If I'm creating a UIView programmatically and I wish to change the UIView properties (background, for example, or actually, messing with CALayers), must I place the code outside of UIView such as in the View controller? Can I put the code somewhere inside UIView?
I was checking out the CoreAnimationKioskStyleMenu example, its code is inside UIView but it's loaded from Nib and can be placed at awakeFromNib, so it doesn't seem to apply to my case.
That depends. Obviously, a good way to handle this is to use a xib file, as it is designed to hold data like this, but that isn't always the best answer for every situation.
If the view is meant to be reused frequently (like a button, or some widget) throughout the application, its best to store all that customization in a subclass of the UIView.
If its a single larger view that will always be managed by a UIViewController, you can keep some of the information in the UIViewController. However, if you end up subclassing a UIView anyway it's probably best practice to keep the data in the UIView.
As a general note, I believe its worth your time to push as much of this data into a xib using interface builder. Magic values (like colors or sizes) peppered through your code will always be a problem if you want to modify it. I have found modifying a xib to be much easier.
Actually there are some methods where you could place initialization/ customization code.
(void)willMoveToSuperview:(UIView *)newSuperview;
(void)didMoveToSuperview;
will get called as soon as u add the view as a subview to another view, at which point you already have the frame and all the properties, and you can do further customizing as you wish.
(void)layoutSubviews -- generally used for changing subviews' frames and layout organization.
Will get called each time the view needs to be redrawn by the system, or when you specifically call [self setNeedsLayout] on your UIView.
Hope this helps.
I have a nib file where I have a view that contains a background image, a button and another image that covers the full screen (a shadow) that needs to be moved to the front.
On the view, I'm creating child views, and after creating those and adding them using [self addView] I need to move to the front the shadow image.
I'm currently using the tag attribute to find that view, but I'm thinking there's probably a better way, by means of identifying the subviews I add in Interface Builder by some name.
I tries adding a IBOutlet to connect the subview with its parent, but it didn't work (and made no sense, since the subview is already connected to its parent in some way).
The IBOutlets way should work, and is probably the best way to do it. Make sure you made the proper connection in Interface Builder after you declared them in the .h file.
The iPhone does a lazy loading of view controllers. The nib might not have been loaded in initWithCoder or any init method for that matter as Kendall specified.
viewDidLoad is the preferred place to access anything from the nib if you want to access them before the view is displayed.
Hope that helps.
At what point are you trying to access the subviews? If you try within init of a ViewController, the IBOutlets will be nil. The first method you can get at them is probably viewDidLoad.
The reason it does make sense to do things this way is that IBOutlets are just direct pointers to some component, even if they are already subviews of something else. Just saves a lot of hunting.
Using the Tag is a perfectly valid way to locate specific views, so long as you're using the viewWithTag: method. If you're already using tags, there's no need to change to IBOutlets unless you just don't like calling viewWithTag:.