Failed that ImageView in scrollView zoom in by swift3 - ios

Question

Sorry I am new to swift and I have an imageView.
I can see my image in imageView.
I want to be able to zoom the image in and out. But I also fail to change my image size. What's wrong with my code? Sorry,I already find many solution to fix my problem. I don't know how to fix it. Should I add some gestureRecognizer or anything else?
Thank for answer.
This is code:
import UIKit
import SnapKit
class ImageViewController: UIViewController, UIScrollViewDelegate {
var url:String = ""
var id:String = ""
var scrollView:UIScrollView = { () -> UIScrollView in
let ui = UIScrollView()
ui.backgroundColor = UIColor.black
ui.minimumZoomScale = 1.0
ui.maximumZoomScale = 6.0
return ui
}()
var toolbar:UIToolbar = { () -> UIToolbar in
let ui = UIToolbar()
ui.barTintColor = defaultNavBackgroundColor
ui.clipsToBounds = true
ui.isTranslucent = false
ui.isUserInteractionEnabled = true
return ui
}()
var photoImageView:UIImageView = { () -> UIImageView in
let ui = UIImageView()
ui.backgroundColor = UIColor.clear
ui.layer.masksToBounds = true
ui.contentMode = .scaleAspectFit
ui.isUserInteractionEnabled = true
return ui
}()
var buttonDownload:UIBarButtonItem = { () -> UIBarButtonItem in
let ui = UIBarButtonItem()
ui.style = .plain
return ui
}()
override func loadView() {
super.loadView()
view.backgroundColor = UIColor.black
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
}
override func viewDidLoad() {
super.viewDidLoad()
// navigationItem.title = name
self.automaticallyAdjustsScrollViewInsets = false
imageFromUrl(imageView: photoImageView, url: url, chatroomId: id,isResize: false)
self.buttonDownload.action = #selector(btnDownloadClicked(sender:))
scrollView.delegate = self
scrollView.contentSize = (self.photoImageView.image!.size)
photoImageView.center = scrollView.center
loadContent()
loadVFL()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func loadContent() {
toolbar.sizeToFit()
let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: self, action: nil)
buttonDownload = UIBarButtonItem(barButtonSystemItem: .action, target: self, action: nil)
toolbar.items = [flexSpace,buttonDownload]
view.addSubview(scrollView)
view.addSubview(toolbar)
scrollView.addSubview(photoImageView)
}
func loadVFL() {
scrollView.snp.makeConstraints { (make) -> Void in
make.top.equalToSuperview()
make.bottom.equalTo(toolbar.snp.top)
make.left.equalToSuperview()
make.right.equalToSuperview()
}
photoImageView.snp.makeConstraints { (make) -> Void in
make.top.equalToSuperview()
make.bottom.equalToSuperview()
make.left.equalToSuperview()
make.right.equalToSuperview()
make.centerX.equalToSuperview()
make.centerY.equalToSuperview()
}
toolbar.snp.makeConstraints { (make) -> Void in
make.width.equalToSuperview()
make.bottom.equalToSuperview()
make.height.equalTo(44)
}
}
func btnDownloadClicked(sender:UIBarButtonItem) {
print("press")
}
// MARK: - UIScrollViewDelegate
func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
return photoImageView
}
}
image like this