iOS Objective C ScrollView - ios

Question

I am trying to implement a UIScrollView and load it with images from an array of images in Xcode using objective-C, each image in the UIScrollView must be full screen both in portrait and in the landscape mode.I have been able to make it work in portrait mode but not in landscape mode. It should be fullscreen in all iOS device sizes. Below is the code I have written so far. I have UIScrollView in my storyboard, a button and a label. Any answer or pointing to a tutorial that implements this will be appreciated. Thanks in advance.
CGRect screen = [[UIScreen mainScreen] bounds];
CGFloat widthInPixel = screen.size.width;
CGFloat heightInPixel = screen.size.height;
float increaseAmount = widthInPixel;
self.imageScrollView.contentMode = UIViewContentModeScaleAspectFit;
self.imageScrollView.pagingEnabled = YES;
[self.imageScrollView setAlwaysBounceVertical:NO];
[self.imageScrollView setAlwaysBounceHorizontal:NO];
imageViews = [[NSMutableArray alloc] init];
self.imageScrollView.clipsToBounds = YES;
NSInteger imageNumbers = [self.images count];
UIImageView *image;
for(NSInteger i = 0; i < imageNumbers; i++) {
CGFloat xOrigin = i * self.view.frame.size.width;
image = [[UIImageView alloc] initWithFrame:
CGRectMake(xOrigin, 0,
widthInPixel,
self.imageScrollView.frame.size.height)];
image.contentMode = UIViewContentModeScaleAspectFit;
image.clipsToBounds = YES;
image.image = self.images[i];
[image setAutoresizingMask:
UIViewAutoresizingFlexibleWidth |
UIViewAutoresizingFlexibleHeight];
[self.imageScrollView addSubview:image];
}
self.imageScrollView.contentSize = CGSizeMake(image.frame.size.width *
imageNumbers,
self.imageScrollView.frame.size.height);

Answer 1

You really should learn how to use auto-layout and constraints. Use your favorite search engine and search for ios auto layout tutorial ... you'll find plenty of material.
Edit:
Scroll offset is an inherent issue when rotating a scroll view with paging enabled. See the edit below for an implementation of viewWillTransitionToSize.
But, to give you an idea, this will do what you want, including auto-resizing on device rotation:
//
// ViewController.m
// ScrollingImages
//
// Created by Don Mag on 7/19/18.
//
#import "ViewController.h"
#interface ViewController ()
#property (strong, nonatomic) IBOutlet UIScrollView *theScrollView;
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSArray *images = #[#"a", #"b", #"c", #"d", #"e"];
[_theScrollView setPagingEnabled:YES];
[_theScrollView setAlwaysBounceVertical:NO];
[_theScrollView setAlwaysBounceHorizontal:NO];
// we'll use this to hold the most recently added view
UIImageView *prevImageView = nil;
for (int i = 0; i < images.count; i++) {
// create an image view with named image from array
UIImageView *v = [[UIImageView alloc] initWithImage:[UIImage imageNamed:images[i]]];
// we want to use auto-layout
v.translatesAutoresizingMaskIntoConstraints = NO;
// we want aspect-fit
v.contentMode = UIViewContentModeScaleAspectFit;
// add it to the scroll view
[_theScrollView addSubview:v];
// set width and height constraints equal to the scroll view
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0] setActive:YES];
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeHeight
multiplier:1.0
constant:0.0] setActive:YES];
if (i == 0) { // if it's the first image
// add top constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0.0] setActive:YES];
// and leading constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:0.0] setActive:YES];
} else {
// constrain leading to previous image view trailing
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:prevImageView
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:0.0] setActive:YES];
// and top to previous image view top
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:prevImageView
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0.0] setActive:YES];
}
if (i == images.count - 1) { // if it's the last image
// add trailing constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:0.0] setActive:YES];
// and bottom constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0.0] setActive:YES];
}
// reference to most recently added view
prevImageView = v;
}
}
- (void) viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
[super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
// execute before rotation
// get the "index" of the current image in the scroll view
NSUInteger idx = (unsigned)(_theScrollView.contentOffset.x / _theScrollView.frame.size.width);
[coordinator animateAlongsideTransition:^(id _Nonnull context) {
// execute during rotation
// update the scroll view's contentOffset, based on the "index"
self.theScrollView.contentOffset = CGPointMake(idx * self.theScrollView.frame.size.width, 0);
} completion:^(id _Nonnull context) {
// execute after rotation (if additional code wanted)
}];
}
#end
You can download a working example project here: https://github.com/DonMag/ScrollingImages