1024 x 768

View controller lifecycle @ University iOS Meetup

December 2, 2014

9 slides

=Overpass

bebas neue =

image

When will then be now?

Ben Gohlke December 2, 2014 university ios

View Controller Lifecycle

View Lifecycle

• UIViewController loads its view programmatically or via storyboard/nib.

• Several methods are called on UIViewController instance to provide an opportunity for customization.

• Layout

• Content

December 2, 2014 university ios

Programmatic Initialization

• Override loadView method in your view controller.

• Do NOT call super on loadView

• Create a root view object and set its frame (usu. same as window or container)

• Create any subviews and add them to their parent using addSubview:

• If using autolayout, add constraints to subviews

• If not, use viewWillLayoutSubviews and viewDidLayoutSubviews

December 2, 2014 university ios

Load from a nib or storyboard

• Lay out subviews in nib or storyboard

• Xcode packages these objects in an archive which is unpacked at runtime. Your app will gain control of fully instantiated and configured objects.

• Not necessarily laid out though.

December 2, 2014 university ios

@interface MyViewController()

@property (nonatomic) IBOutlet UIButton *myButton; @property (nonatomic) IBOutlet UIButton *myTextField; - (IBAction)myAction:(id)sender;

@end

Tweaking the layout

• viewWillLayoutSubviews, called right before subviews are laid out. Opportunity to override and make changes to view before layout.

• viewDidLayoutSubviews, called right after subviews are laid out (not guaranteed that all subviews have adjusted their layouts).

December 2, 2014 university ios

- (void)viewWillLayoutSubviews {

[super viewWillLayoutSubviews]; if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) self.view.superview.bounds = CGRectMake(0, 0, 540, 400); }

- (void)viewDidLayoutSubviews {

[super viewDidLayoutSubviews]; if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { CGFloat imageViewWidth = CGRectGetWidth(self.anImageView.bounds); CGFloat multiplier = imageViewWidth / self.anImageView.image.size.width; CGFloat adjustedHeight = ceilf(self.anImageView.image.size.height * multiplier);

[self.anImageViewHeightConstraint setConstraint:adjustedHeight]; } }

Demo

December 2, 2014 university ios

https://github.com/jcgohlke/University-iOS-Demo-December

@AkhenatenQuestions?

December 2, 2014 university ios