Scroll second Scrollview when first ScrollView did scroll

Question

I have two ScrollViews in my Project and they should scroll at the same time. It should work when I scroll the myFriendsScrollView.

That is my unfinished code:

import Foundation
import UIKit

class profileController: UIViewController {

@IBOutlet weak var myFriendsScrollView: UIScrollView!
@IBOutlet weak var myFriendsNameScrollView: UIScrollView!

override func viewDidLoad() {
    super.viewDidLoad()

    // My Scrollview One
    let myFriendsScrollViewHeight = self.myFriendsScrollView.frame.height
    let myFriendsScrollViewWidth = self.myFriendsScrollView.frame.width

    let myFriendImg1 = UIImageView(frame: CGRect(x: 0, y: 0, width: myFriendsScrollViewWidth/4, height: myFriendsScrollViewHeight))
    let myFriendImg2 = UIImageView(frame: CGRect(x: 100 , y: 0, width: myFriendsScrollViewWidth/4, height: myFriendsScrollViewHeight))  
    let myFriendImg3 = UIImageView(frame: CGRect(x: 200 , y: 0, width: myFriendsScrollViewWidth/4, height: myFriendsScrollViewHeight))

    self.myFriendsScrollView.addSubview(myFriendImg1)
    self.myFriendsScrollView.addSubview(myFriendImg2)
    self.myFriendsScrollView.addSubview(myFriendImg3)

    myFriendImg1.image = UIImage(named: "avatar_placeholder");
    myFriendImg2.image = UIImage(named: "avatar_placeholder");
    myFriendImg3.image = UIImage(named: "avatar_placeholder");


    self.myFriendsScrollView.contentSize = CGSize(width: self.myFriendsScrollView.frame.width*2, height: self.myFriendsScrollView.frame.height)
    self.myFriendsScrollView.isPagingEnabled = true

    // My Scrollview Two
    let myFriendsNameScrollViewHeight = self.myFriendsNameScrollView.frame.height
    let myFriendsNameScrollViewWidth = self.myFriendsNameScrollView.frame.width

    let myFriendLbl1 = UILabel(frame: CGRect(x: 0, y: 0, width: myFriendsNameScrollViewWidth/4, height: myFriendsNameScrollViewHeight))
    let myFriendLbl2 = UILabel(frame: CGRect(x: 100 , y: 0, width: myFriendsNameScrollViewWidth/4, height: myFriendsNameScrollViewHeight))
    let myFriendLbl3 = UILabel(frame: CGRect(x: 200 , y: 0, width: myFriendsNameScrollViewWidth/4, height: myFriendsNameScrollViewHeight))

    self.myFriendsNameScrollView.addSubview(myFriendLbl1)
    self.myFriendsNameScrollView.addSubview(myFriendLbl2)
    self.myFriendsNameScrollView.addSubview(myFriendLbl3)

    myFriendLbl1.text = "UserName";
    myFriendLbl2.text = "UserName";
    myFriendLbl3.text = "UserName";

    self.myFriendsNameScrollView.contentSize = CGSize(width: self.myFriendsNameScrollView.frame.width*2, height: self.myFriendsNameScrollView.frame.height)
    self.myFriendsNameScrollView.isPagingEnabled = true

}  

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView == myFriendsScrollView {
        myFriendsNameScrollView.contentOffset = scrollView.contentOffset
    }
    else {
        myFriendsScrollView.contentOffset = scrollView.contentOffset
    }
}

}

Thanks for your help.

I think this can help you :- https://stackoverflow.com/questions/41131986/scrollview-gesture-recognizer-swipe-vertically — Akash Singh Sisodia, Jun 28 '17 at 11:11
try surrounding with Main thread , .....see the answer below , do your UI Opration in main thread — Dhiru, Jun 28 '17 at 11:16

Dhiru · Answer 1 · 2017-06-28T11:15:17.697

you can use its delegate method . and set the content OffSet on other ScrollView

  func scrollViewDidScroll(_ scrollView: UIScrollView!) {
            // This will be called every time the user scrolls the scroll view 

       if  myFriendsScrollView ==scrollView 
        {
           let contentOffSet = scrollView.contentOffset

         //change the Off set of other ScrollView   
     // just surround with main thread 

      DispatchQueue.main.async {
         secondScrollView.setContentOffset=contentOffSet;
       }
    }



  }

i hope this will help you

score 1 · Accepted Answer · answered Jun 28 '17 at 11:33

It seems like your implementation of the delegate method is correct already, I've tested in playground and it seems to work great.

However, it doesn't look like it's actually hooked up. Make sure that your class is:

class profileController: UIViewController, UIScrollViewDelegate { ... }

and add in viewDidLoad:

myFriendsScrollView.delegate = self
myFriendsNameScrollView.delegate = self

Scroll second Scrollview when first ScrollView did scroll

2 Answers2