In the viewWillAppear delegate method, I'm setting subview's frames with rects ( location and size).
Now, There is one subview whose content will grow with user actions.
So, I need a callback in that superview controller ( The One I am talking on first sentence) , to update the layout. In this callback, I can find out how much the size increased, and then set other subviews frame rects too.
It can be done through calling setNeedsLayout method on the view, but it requires layoutSubviews to be overridden on the UIView. Please note that it is not a delegate method, I need to have a custom view, Which I don't want to do,
Is there any delegate method for me to update the layout in the view's controller ?
UPDATE:
This need to be support on iOS 4.2
There are two UIViewController methods of possible relevance:
-viewWillLayoutSubviews
-viewDidLayoutSubviews
You can probably guess when they're called.
Related
I'm struggling with setNeedsDisplay. I thought it was supposed to trigger calls of drawRect: for the view for which it is called and the hierarchy below that if it's within the view's bounds, but I'm not finding that to be the case. Here is my setup:
From the application delegate, I create a view whose size is a square that covers essentially the whole screen real estate. This view is called TrollCalendarView. There is not much that happens with TrollCalendarView except for a rotation triggered by the compass.
There are 7 subviews of TrollCalendarView called PlatformView intended to contain 2D draw objects arranged around the center of TrollCalendarView in a 7-sided arrangement. So when the iPad is rotated, these 7 views rotate such that they are always oriented with the cardinal directions.
Each of the PlatformView subviews contains 3 subviews called Tower. Each tower contains 2D draw objects implemented in drawRect:.
So, in summary, I have TrollCalendarView with empty drawRect:, and subviews PlatformView and Platformview -> Tower that each have drawRect implementations. Additionally, Tower lies within the bounds of Platform, and Platform lies within the bounds of TrollCalendarView.
In TrollCalendarView I've added a swipe recognizer. When I swipe happens, a property is updated, and I call [self setNeedsDisplay] but nothing seems to happen. I added NSLog entries to drawRect: method in each of these views, and only the TrollCalendarView drawRect: method is called. Ironically, that is the one view whose drawRect method will be empty.
There is no xib file.
What do I need to do to ensure the drawRect method in the other subviews is called? Is there documentation somewhere that describes all the nuances that could affect this?
I'm struggling with setNeedsDisplay. I thought it was supposed to trigger calls of drawRect for the view for which it is called and the hierarchy below that if it's within the view's bounds
No, that is not the case. Where did you get that idea?
-setNeedsDisplay: applies only to the view to which it is sent. If you need to invalidate other views, you need to add some code to send -setNeedsDisplay: to them, too. That's all there is to it.
I think this is an optimization in the framework; if your subviews don't need to draw again, then this is a major performance improvement. Realize that almost anything animatable does not require drawrect (moving, scaling, etc).
If you know that all of your subviews should be redrawn (and not simply moved), then override setNeedsDisplay in your main view and do like this:
-(void) setNeedsDisplay {
[self.subviews makeObjectsPerformSelector:#selector(setNeedsDisplay)];
[super setNeedsDisplay];
}
I have tested this, and it causes all subviews to be redrawn as well. Please note that you will earn efficiency karma points if you somehow filter your subviews and make sure you only send that to subviews which actually need redrawn... and even more if you can figure out how not to need to redraw them. :-)
From my understanding, setNeedsDisplay only affects the view it's called on. Is there a simple way to say "update this view and all its subviews, recursively?"
In response to the comments, here's my situation: I've got a custom view
#interface ContainerView : UIView
this view does not implement drawRect. In my xib there's an instance (called container) of the ContainerView which has some (custom) subviews added to it. When in the code I say
[container setNeedsDisplay]
I expect these subviews to update. Where am I wrong?
Ok, UIView draws itself when its first displayed. CALayers do not. Calling setNeedsDisplay on a UIView marks it as dirty, this automatically redraws all SubViews as well (calling drawrect on all subviews). Calling setNeedsDisplay on a CALayer doesn't have the same effect, it wont redraw sublayers. Hope this helps.
Regards
Ref
iOS 7 Programming Pushing the Limits By Rob Napier, Mugunth Kumar
UIView Class Reference
The UIView class defines a rectangular area on the screen and the interfaces for managing the content in that area. At runtime, a view object handles the rendering of any content in its area and also handles any interactions with that content
setNeedsDisplay
Marks the receiver’s entire bounds rectangle as needing to be redrawn.
Note: If your view is backed by a CAEAGLLayer object, this method has no effect. It is intended for use only with views that use native drawing technologies (such as UIKit and Core Graphics) to render their content.
The subviews are inside the bounds of the view, so the view will ask it's subview what to display.
Have you try and encounter some case that go agains this definition?
If you are implementing your own UIView subclass you need to handle all the display yourself in drawRect:
I have a customized View Controller (we'll call it the wrapper). Its view contains only a UIScrollView. The scroll view contains another customized view controller (we'll call it the inside view), initialized from an xib file (the scroll view itself is initialized from a xib file as well, but I don't believe it matters).
The wrapper view is displayed using a UITabBarController, which contains several more similar view controllers.
I have this weird problem: the wrapper's rotation functions - shouldAutoRotate, willAnimateRotation - get called every time that I rotate the device. For some reason, the inside view's rotation functions don't get called, but it still rotates. The inside view's shouldAutoRotate does get called when initializing it (when the app starts).
I've looked at google and couldn't find anything that is relevant to my case. I'm not sure if it is related, but the Autoresize subviews is checked on all xib files.
I'd be glad if you could help me solve this problem. I need the inside view's rotation function to get called on rotation in order to arrange it manually, but I'd like to avoid calling them from the wrapping view (rather it to work as it should).
Thank you in advance!
Well the innerViewController's rotation function will not be called because they are added as subview's to your scrollView what you can do is generate a NSNotification when orientation changes in your parent controller then you can receieve notification in subview and manage them accordingly. Or you can iterate through subviews of UIScrollView when your shouldAutoRoatate called in you parent controller and then manually call should autorotate method of child views. Hope you understand.
The simplest way is to hold some UIInnerViewController* innerController in your .h file and in .m to call inner's
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation inside of the wrapper like so:
wrapper.m
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation{
BOOL innerResult = [innerController shouldAutorotateToInterfaceOrientation:interfaceOrientation];
//may be more computations here
return innerResult;// or any other value, based on your needs
}
Other approach that you may use is to register inner controller to UIDeviceOrientationDidChangeNotification like so:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(orientationChanged:)
name:UIDeviceOrientationDidChangeNotification
object:nil];
and layout subviews in -(void)orientationChanged:(NSNotification*)notification;in the same inner controller. The only thing you should be awere of, is that UIDeviceOrientation is a little-bit different than UIInterfaceOrientation and may hold value such UIDeviceOrientationFaceUp that is not applicable to UI changes in most cases.
Nesting viewcontrollers inside custom viewcontrollers is not supported in iOS 4. You can usually forward all the necessary messages to your child VC's manually, though, with acceptable results.
I have my view set up in viewDidLoad. All the different frames and such of the subviews have been defined relative to self.view. Therefore it doesn't matter what size self.view is the subviews will always shrink or expand to fit (as it were).
So when I rotate my device I want the view to rotate (easy enough with shouldAutoRotateToInterfaceOrientation:...) but the subviews stay the same shape.
Calling [self viewDidLoad]; makes all the elements fit, but puts a new layer on top of the previous layout (which is obvious... but i'm just saying to explain what I mean).
Is there any way to refresh the frames of the subviews or something? I don't know what other people do to be honest. Am I going to have to put ALL of my views into the .h file as properties and do everything manually on didRotate...?
You have three options:
If autoresizing masks are good enough to position your views, assign the correct autoresizing mask to each subview when you create them.
If autoresizing masks are not sufficient, override willAnimateRotationToInterfaceOrientation:duration: and reposition your subviews in that method. I would create a custom method that takes the orientation as a parameter and is responsible for laying out all subviews. You can then call this method from willAnimateRotationToInterfaceOrientation:duration: and from viewDidLoad.
You could also create a custom UIView subclass and make your view controller's view an instance of this class. Then override layoutSubviews to position all subviews depending on the view's size. This approach implies that your custom view manages its subviews instead of the view controller.
I subclassed UIScrollView (IPhone SDK) and overrode the (void)layoutSubviews; method.
I noticed that each time the scrollView is scrolled, this method is called.
Is that the correct behaviour or do I have mistakes in my code? If it is the default behaviour, isn't this a performance killer?
Sincerely,
heinrich
It is the correct behaviour and it should be used to get a custom layout of your subviews. I have used it several times and haven't had any performance issues eaven with hundreds of items added.
A cut-out from the documentation on that topic:
Subclasses can also be containers for
other views. In this case, just
override the designated initializer,
initWithFrame:, to create a view
hierarchy. If you want to
programmatically force the layout of
subviews before drawing, send
setNeedsLayout to the view. Then when
layoutIfNeeded is invoked, the
layoutSubviews method is invoked just
before displaying. Subclasses should
override layoutSubviews to perform
any custom arrangement of subviews.