Scroll view moving to the center of a specific Button

ViewController.swift

//
//  ViewController.swift
//  ButtonsAnimate
//
//  Created by LEE HAEUN on 2019/12/12.
//  Copyright © 2019 LEE HAEUN. All rights reserved.
//

//코드 설명
//submit 버튼을 누르면 scrollview가 false인 버튼을 찾아서 그 중앙으로 이동하는 소스
//만약 scrollview의 프레임 중앙보다 작은 값일 때도 false 인 버튼이 중앙으로 올 수 있도록 
//비어있는 UIView의 topViewHeight의 height을 조절해서 중앙으로 올 수 있게 함
//scrollview의 y 위치가 비어있는 UIView 에 값보다 커지면 height을 0으로 줘 원 상태로 바꾼다.
//또한 tag 를 지정해서 tag값으로 button 을 찾아 그 button 의 midY 를 구한다.

import UIKit

class ViewController: UIViewController {
  
  var topViewHeight: NSLayoutConstraint?
  var check: [Bool] = [false,false,false,false]
  override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    layout()
  }
  func layout() {
    view.addSubview(scrollView)
    scrollView.addSubview(stackView)
    stackView.addArrangedSubview(topView)
    stackView.addArrangedSubview(button0)
    stackView.addArrangedSubview(button1)
    stackView.addArrangedSubview(button2)
    stackView.addArrangedSubview(button3)
    stackView.addArrangedSubview(submit)
    
    topViewHeight = topView.heightAnchor.constraint(equalToConstant: 0)
    topViewHeight?.isActive = true
    NSLayoutConstraint.activate([
      scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
      scrollView.leftAnchor.constraint(equalTo: view.leftAnchor),
      scrollView.rightAnchor.constraint(equalTo: view.rightAnchor),
      scrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
      
      stackView.topAnchor.constraint(equalTo: scrollView.topAnchor),
      stackView.leftAnchor.constraint(equalTo: view.leftAnchor),
      stackView.rightAnchor.constraint(equalTo: view.rightAnchor),
      stackView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
      
      button0.heightAnchor.constraint(equalToConstant: 300),
      button1.heightAnchor.constraint(equalToConstant: 300),
      button2.heightAnchor.constraint(equalToConstant: 300),
      button3.heightAnchor.constraint(equalToConstant: 300),
      submit.heightAnchor.constraint(equalToConstant: 300),
    ])
  }
  
  lazy var scrollView: UIScrollView = {
    let scroll = UIScrollView()
    scroll.translatesAutoresizingMaskIntoConstraints = false
    scroll.backgroundColor = .white
    scroll.delegate = self
    return scroll
  }()
  lazy var stackView: UIStackView = {
    let stack = UIStackView()
    stack.translatesAutoresizingMaskIntoConstraints = false
    stack.axis = .vertical
    return stack
  }()
  lazy var topView: UIView = {
    let view = UIView()
    view.translatesAutoresizingMaskIntoConstraints = false
    return view
  }()
  lazy var button0: UIButton = {
    let btn = UIButton()
    btn.translatesAutoresizingMaskIntoConstraints = false
    btn.setTitle(String(check[0]), for: .normal)
    btn.tag = 1
    btn.addTarget(self, action: #selector(buttonEvent), for: .touchUpInside)
    btn.backgroundColor = .red
    return btn
  }()
  lazy var button1: UIButton = {
    let btn = UIButton()
    btn.translatesAutoresizingMaskIntoConstraints = false
    btn.setTitle(String(check[1]), for: .normal)
    btn.tag = 2
    btn.addTarget(self, action: #selector(buttonEvent), for: .touchUpInside)
    btn.backgroundColor = .orange
    return btn
  }()
  lazy var button2: UIButton = {
    let btn = UIButton()
    btn.translatesAutoresizingMaskIntoConstraints = false
    btn.setTitle(String(check[2]), for: .normal)
    btn.tag = 3
    btn.addTarget(self, action: #selector(buttonEvent), for: .touchUpInside)
    btn.backgroundColor = .green
    return btn
  }()
  lazy var button3: UIButton = {
    let btn = UIButton()
    btn.translatesAutoresizingMaskIntoConstraints = false
    btn.setTitle(String(check[3]), for: .normal)
    btn.tag = 4
    btn.addTarget(self, action: #selector(buttonEvent), for: .touchUpInside)
    btn.backgroundColor = .purple
    return btn
  }()
  lazy var submit: UIButton = {
    let btn = UIButton()
    btn.translatesAutoresizingMaskIntoConstraints = false
    btn.setTitle("submit", for: .normal)
    btn.addTarget(self, action: #selector(submitEvent), for: .touchUpInside)
    btn.backgroundColor = .black
    return btn
  }()
}

extension ViewController {
  @objc func buttonEvent(sender: UIButton) {
    print(check)
    check[sender.tag - 1] = !check[sender.tag - 1]
    print(check)
    sender.setTitle(String(check[sender.tag - 1]), for: .normal)
    
  }
  @objc func submitEvent(){
    //    print(button0.frame.midY)
    //    print(button1.frame.midY)
    //    print(button2.frame.midY)
    //    print(button3.frame.midY)
    for i in 0..<check.count {
      print("index: \(i)")
      if !check[i]{
        if let falseButton = self.view.viewWithTag(i + 1) as? UIButton {
          print("스크롤뷰 전체 크기\(scrollView.contentSize.height)")
          print("중앙값 \(falseButton.frame.midY)")
          moveOffset(yPoint: CGPoint(x: 0, y: Int(falseButton.frame.midY)))
          break
        }
      }
    }
  }
  func moveOffset(yPoint: CGPoint){
    print(scrollView.frame.height)
    print(yPoint.y)
    print((self.scrollView.frame.height/2) - yPoint.y)
    if yPoint.y < (scrollView.frame.height/2) {
      self.topViewHeight?.constant = (self.scrollView.frame.height/2) - yPoint.y
      UIView.animate(withDuration: 0.33) {
        self.scrollView.contentOffset = .zero
        self.view.layoutIfNeeded()
      }
    }else{
      UIView.animate(withDuration: 0.33) {
        let y = (self.scrollView.frame.height/2) - yPoint.y
        self.scrollView.contentOffset = CGPoint(x: 0, y: y < -1 ? y*(-1):y)
        UIView.animate(withDuration: 0.33) {
          self.view.layoutIfNeeded()
        }
      }
    }
  }
}


extension ViewController: UIScrollViewDelegate {
  func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView.contentOffset.y  > topViewHeight!.constant {
      topViewHeight?.constant = 0
    }
  }
}

우와 ㅋㅋㅋㅋ 아이폰데브에 글 올렸던 유저인데... 감사합니다!