I have a class called SKButton, subclass of SKSpriteNode, which implements the touchesBegan() function to print("hello"). But when i add an SKButton object to my view, touchesBegan() never gets called on the button. Why?
You need to make sure that userInteractionEnabled is enabled on all of the superviews of your view.
Also keep in mind that coming from Swift 2.3 to Swift 3 in your project might trigger the warning for the name of the method, you update it using the default fix and then you end up like me wondering why the methods related to touches are not called despite of the fact that you set userInteractionEnabled. Fix: make sure that method name is written as per your current version of Swift!
Related
Does anyone know why UITextView.layoutSubviews() is not called when rotating a device to portrait mode?
When rotating to landscape mode, these are called:
UIViewController.viewWillTransition
UIViewController.viewDidLayoutSubviews
UITextView.layoutSubviews
UILabel.layoutSubviews
But when rotating back to portrait, the UILabel.layoutSubviews() is called, but not the UITextView.layoutSubviews. This is in an empty project with no other code apart from traces in these methods.
layoutSubviews is usually called when setNeedsLayout() is invoked already in the previous invocation of run loop.
If the layout system does not think it needs to be called, it will not be called.
Ideally you should not override this function. You should just call setNeedsLayout() after making superview changes, and let the layout system call the default implementation of this function. Morever, you should define your subview layout needs inside auto-layout so it is able to get correct values from there.
If you want immediate update, you should call layoutIfNeeded().
This is because this is one of those methods that are called arbitrarily by UIKit framework and it may not be ideal for your layout needs.
There are 2 separate things here.
Understanding layoutSubviews(). I.e. when and where to use it.
How to achieve what you want to do the right way. I.e. doing something with the UITextView at device rotation.
About the layoutSubviews(), you should not put any logic here as your view is not having any sub views.
You may say that we expect iOS to call it, so we can put some implementation here, but again, that is not the right way. layoutSubviews() is not meant to alter the view itself, but just laying out sub views.
I would recommend reading more on layoutSubviews(). I learnt from here, when I started learning iOS.
Now to achieve what you want to do, i.e. do something at the time of device rotation, you proper way is to use viewWillTransition(to:with:) method of UIViewController.
In this method, you can put logic to do something just before the transition will happen.
And you can also put logic which will execute during the transition OR after the transition completes, using the UIViewControllerTransitionCoordinator parameter passed to viewWillTransition(to:with:)
Hope this helps!
I have been searching around for this particular method:didMoveToWindow() however I haven't found any concrete information.
Could someone explain why and when should someone use this method and when is it called?
This method is called by iOS when a UIView is added to the Window object.
You are supposed to override it to make your app do something at the same that.
The default implementation of this method does nothing. Subclasses can
override it to perform additional actions whenever the window changes.
The window property may be nil by the time that this method is called,
indicating that the receiver does not currently reside in any window.
This occurs when the receiver has just been removed from its superview
or when the receiver has just been added to a superview that is not
attached to a window. Overrides of this method may choose to ignore
such cases if they are not of interest.
https://developer.apple.com/reference/uikit/uiview/1622527-didmovetowindow
I have a case where I need to modify all instances of NSView, trivial by adding a couple of lines of code to init() but how can that be done cleanly for all subclasses in Swift?
The case I have in mind:
I add a custom property to NSView via an extension
That works fine, but isn't animatable until it's registered as animatable via the layer's addAnimation:forKey: method.
So all I really need to do is ensure that addAnimation:forKey: gets called every time NSView or a subclass gets called.
Things I've considered:
Somehow doing this in an extension. Problem: extensions can't override functions, and without overriding init() or something like viewDidAppear() the code has to be called manually every time (e.g. with a convenience initialiser).
Subclass NSView and add the code. Problem: NSButton, Slider and all the rest won't inherit the code, and I have to subclass them all.
Method swizzling. This should be possible, because obj-c methods are swizzlable and NSView inherits from NSObject.
So far only swizzling seems viable, but I'm reluctant to do this because it's reliant on the APIs staying obj-c friendly, and I don't know how long that will be the case for.
Is there another way?
Where should I customise my IBOutlets?
Say I have created a button with interface builder, created an IBOutlet for it and I would want to change a property during runtime (ex: background color or localized title).
I would think of adding it to the viewDidLoad method, but outlets aren't yet created.
I remember having nil outlets in viewDidLoad, but I might be wrong.
If I move it viewWillAppear, the code will be executed every time the view controller's view appears.
Is there any better place for my IBOutlet related code, so it's only executed once?
Obviously I can do just about any customization using only the interface builder and making use of the User defined runtime attributes or localized stroryboards, but I don't like that since it's much more tedious to change later.
From the Doc
Its clearly says about the Views loaded into the memory in the -viewDidLoad() delegate itself.
I would think of adding it to the viewDidLoad method, but outlets
aren't yet created.
It is a false statement, Because you only get the viewDidLoad: message after IBOutlets are created. So you can safely do any customization in viewDidLoad:
Let’s say you have a Button you want to customise. You put the button at the place where you want it to be and then open the “Identity Inspector” on the right.
There is a textfield for “Custom Class”:
I usually create a subclass of UIButton / NSButton (depending on iOS or OSX) and edit the behaviour, drawing methods and functionality in this class file. Then just add the name of this class in this textfield. Voila!
I was wondering if I can call willMoveToSuperview on UIView and after that retain that view to reuse later for one ? something like following
if (!CGRectIntersectsRect(cell.frame, visibleRegion)) {
[cell willMoveToSuperview:nil];
[self.resuableCells addObject:cell];
}
I am not sure about your intent here...
But WillMoveToSuperview - According to doc:
The default implementation of this method does nothing. Subclasses can override it to perform additional actions whenever the superview changes.
So your code,
[cell willMoveToSuperview:nil];
Has no effect unless you override this method in a cell subclass and implement your own logic there.
Coming to your question -
Does willMoveToSuperview will also deallocate the UIView on which its got called?
Answer is obvious - NO.
willMoveToSuperview is an observer method that the system calls as a courtesy to you in order to give you a chance to handle special cases before it completes some other hidden tasks.
It's default behavior is to do nothing, but you might want to tidy up something in your code prior to a move by overriding this method.
A proper use case might be if you had a view playing a video clip or an animation, and something else in your code is about to rip the view out of it's current hierarchy and place it in some other un-related view hierarchy. You might want the chance to pause the clip or suspend the animation before the move took place.
I doubt it's the right method to handle what you are attempting, and I definitely know you should not be calling it directly.
Feel free to post some more code to show us what you're trying to accomplish and where it's going wrong.