IOS Swift4 Not able to scroll a ScrollView - ios

Question

I hv been trying to make a scrollview scroll, just to the extent that the scrollview is supposed to show. However, I am not able to. This is my code.
func setupMainView() {
// This is where the image view and other UIViews which are supposed to go in the contentview are set up
self.setupImagesView()
self.setupView1()
self.setupView2()
self.setupView3()
self.setupView4()
self.scrollView = UIScrollView()
self.scrollView.backgroundColor = UIColor.white
self.view.addSubview(self.scrollView)
self.automaticallyAdjustsScrollViewInsets = false
self.scrollView.contentInset = UIEdgeInsets.zero
self.scrollView.scrollIndicatorInsets = UIEdgeInsets.zero;
self.contentView = UIView()
self.scrollView.layer.masksToBounds = false
self.scrollView.backgroundColor = UIColor.white
self.scrollView.layer.borderWidth = 0
self.scrollView.layer.borderColor = UIColor.white.cgColor
self.view.addSubview(scrollView)
self.contentView.addSubview(imagesScrollView)
self.contentView.addSubview(view1)
self.contentView.addSubview(view2)
self.contentView.addSubview(view3)
self.contentView.addSubview(view4)
self.scrollView.addSubview(contentView)
self.scrollView.contentInset = UIEdgeInsets.zero
self.scrollView.scrollIndicatorInsets = UIEdgeInsets.zero;
var scrollViewHeight:CGFloat = 0.0;
for _ in self.scrollView.subviews {
scrollViewHeight += view.frame.size.height
}
var newHeight = scrollViewHeight * 1.1 + offset + 100
scrollView.contentSize = CGSize(width:screenWidth, height:newHeight)
scrollView.reloadInputViews()
}
The views are getting loaded etc, but I am not manage the scroll. It somehow either too little or too much.
Now, I tried setting the height of contentSize to scrollViewHeight and double of that etc. What I notice is that there is no predictability of how much it will scroll. Change from 1.1 to 1.6 .. there is too much whitescreen below the views, change it to 1.1 or 1.2 it does not even scroll to the bottom.
Note, everything has been set up programmatically, without storyboard etc.
Also note that I need to support all IOS devices with version > 10.
Am a little lost here. What am I doing wrong?

Answer 1

This is a very old way of configuring a scroll view - you should be using auto-layout.
And, you're doing a number of things wrong...
First, we'll assume you are setting frames of the various subviews in code you haven't shown.
However, the code you have shown creates a scrollView and adds it to self.view -- but you never set the frame of the scroll view.
Also, this part of your code:
for _ in self.scrollView.subviews {
scrollViewHeight += view.frame.size.height
}
you've added several views as subviews of contentView, then added contentView as the only subview of scrollView.
And... you are trying to increment scrollViewHeight by the height of your root view instead of the height of the scrollView's subviews.
So, scrollViewHeight will only be the height of self.view.
What you probably want to do is sum the heights of contentView.subviews:
var contentViewHeight: CGFloat = 0
for v in contentView.subviews {
contentViewHeight += v.frame.height
}
contentView.frame.size.height = contentViewHeight
then set the scrollView's contentSize.height to the height of contentView's frame.
Here is a very, very basic example, using explicitly set frame sizes -- again, though, you should start using auto-layout:
class SimpleScrollViewController: UIViewController {
var imagesScrollView: UIView!
var view1: UIView!
var view2: UIView!
var view3: UIView!
var view4: UIView!
var contentView: UIView!
var scrollView: UIScrollView!
override func viewDidLoad() {
super.viewDidLoad()
setupMainView()
}
func setupMainView() {
// This is where the image view and other UIViews which are supposed to go in the contentview are set up
self.setupImagesView()
self.setupView1()
self.setupView2()
self.setupView3()
self.setupView4()
self.scrollView = UIScrollView()
// let's use a color other than white so we can see the frame of the scrollView
self.scrollView.backgroundColor = UIColor.cyan
self.view.addSubview(self.scrollView)
self.automaticallyAdjustsScrollViewInsets = false
self.scrollView.contentInset = UIEdgeInsets.zero
self.scrollView.scrollIndicatorInsets = UIEdgeInsets.zero;
self.contentView = UIView()
self.contentView.backgroundColor = UIColor.lightGray
self.scrollView.layer.masksToBounds = false
self.scrollView.layer.borderWidth = 0
self.scrollView.layer.borderColor = UIColor.white.cgColor
self.view.addSubview(scrollView)
self.contentView.addSubview(imagesScrollView)
self.contentView.addSubview(view1)
self.contentView.addSubview(view2)
self.contentView.addSubview(view3)
self.contentView.addSubview(view4)
self.scrollView.addSubview(contentView)
self.scrollView.contentInset = UIEdgeInsets.zero
self.scrollView.scrollIndicatorInsets = UIEdgeInsets.zero;
var contentViewHeight: CGFloat = 0
for v in contentView.subviews {
contentViewHeight += v.frame.height
}
contentView.frame.size.height = contentViewHeight
// don't know what you're doing here....
//scrollView.reloadInputViews()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
// here is where you know the frame of self.view
// so, make the scroll view cover the entire view
scrollView.frame = view.frame
// now, make contentView width equal to scrollView width
contentView.frame.size.width = scrollView.frame.size.width
// set the scrollView's content size
scrollView.contentSize = contentView.frame.size
}
func setupImagesView() -> Void {
imagesScrollView = UIView()
imagesScrollView.backgroundColor = .red
imagesScrollView.frame = CGRect(0, 0, 300, 100)
}
func setupView1() -> Void {
view1 = UIView()
view1.backgroundColor = .green
view1.frame = CGRect(20, imagesScrollView.frame.maxY, 300, 200)
}
func setupView2() -> Void {
view2 = UIView()
view2.backgroundColor = .blue
view2.frame = CGRect(40, view1.frame.maxY, 300, 250)
}
func setupView3() -> Void {
view3 = UIView()
view3.backgroundColor = .yellow
view3.frame = CGRect(60, view2.frame.maxY, 200, 275)
}
func setupView4() -> Void {
view4 = UIView()
view4.backgroundColor = .orange
view4.frame = CGRect(80, view3.frame.maxY, 200, 100)
}
}

Answer 2

If I remember correctly you need to in order for scroll view to work you need to implement a couple of delegate methods. You also need a couple of properties set.
contentSize is one
and I think min and max size
see: https://developer.apple.com/documentation/uikit/uiscrollviewdelegate
also see Stanford University's
Paul Hagarty Developing IOS 11 apps with swift episode 9 for loads of information on UIScrollView
https://www.youtube.com/watch?v=B281mrPUGjg
seek to about 31mins for the scroll view information.

Answer 3

This may help in the setup of UIScrollView programatically:
https://sheikhamais.medium.com/how-to-use-the-new-uiscrollview-programmatically-baf270ee9b4