WKWebview & UIImageView Inside UIScrollView programmatically autolayout Objective-C - ios

Question

I wanted to implement WKWebView and UIImageView Inside a UIScrollView programmatically, but it doesn't fulfill my requirement.I first add UIImageView & WKWebView to scrollView after that I added the scrollView to ViewController subview. I write the Objective-C code for it as below.
#import "StoryDetailViewController.h"
#import <WebKit/WebKit.h>
#interface StoryDetailViewController ()
//#property(strong,nonatomic) WKWebView *webView;
#end
#implementation StoryDetailViewController{
UIScrollView* scrollView;
WKWebView* webView;
UILabel* title;
UIImageView* imageView;
}
- (void)viewDidLoad {
[super viewDidLoad];
[self setUpSubview];
// Do any additional setup after loading the view.
}
-(void)setUpSubview{
scrollView = [[UIScrollView alloc]init];
scrollView.backgroundColor=[UIColor redColor];
scrollView.translatesAutoresizingMaskIntoConstraints=NO;
imageView=[[UIImageView alloc]init];
imageView.backgroundColor=[UIColor yellowColor];
imageView.translatesAutoresizingMaskIntoConstraints=NO;
webView = [[WKWebView alloc]init];
webView.backgroundColor=[UIColor purpleColor];
webView.translatesAutoresizingMaskIntoConstraints=NO;
[scrollView addSubview:imageView];
[scrollView addSubview:webView];
[self.view addSubview:scrollView];
[self addConstraints];
}
-(void)addConstraints{
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeHeight
multiplier:0.35
constant:0.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeLeft
multiplier:1.0
constant:0.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:webView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:webView
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeLeft
multiplier:1.0
constant:0.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:webView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:imageView
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:10.0]];
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:webView
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:scrollView
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeft
multiplier:1.0
constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:scrollView
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeRight
multiplier:1.0
constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:scrollView
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:scrollView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0.0]];
}
#end
**I'm using the WKwebview because the UIWebView is deprecated in Xcode 9 and WKwebview in storyboard supported only from iOS 11 **
So Please help if code is wrong.

Answer 1

First you want to put this code in viewDidLayoutSubviews
-(void)viewDidLayoutSubviews {
[self setUpSubview];
}
second , you should create a content view inside scrollview and add elements to it but as a work around add these 2 constraints
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeRight
multiplier:1.0
constant:0.0]];
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0]];
and remove this as scrollview expects it's size from sub-elements and not vice versa
[scrollView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:scrollView
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0]];
third give height for the imageView not that equals to scroll view remove it and give a static height or height proportional to self.view
[imageView addConstraint:[NSLayoutConstraint constraintWithItem:imageView
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNone
multiplier:1.0
constant:200.0]];
finally do setp 2,3 with the webview