image for nav bar button item swift

Swift 4 and 5:

let imageView = UIImageView(image: UIImage(named: "Harp"))
let buttonItem = UIBarButtonItem(customView: imageView)
self.navigationItem.leftBarButtonItem = buttonItem

Try This

let button = UIButton(type: UIButtonType.Custom)
button.setImage(UIImage(named: "yourImageName.png"), forState: UIControlState.Normal)
button.addTarget(self, action:Selector("callMethod"), forControlEvents: UIControlEvents.TouchDragInside)
button.frame=CGRectMake(0, 0, 30, 30)
let barButton = UIBarButtonItem(customView: button)
self.navigationItem.leftBarButtonItems = [newBackButton,barButton]

For Swift 3

let button = UIButton.init(type: .custom)
button.setImage(UIImage.init(named: "yourImageName.png"), for: UIControlState.normal)
button.addTarget(self, action:#selector(ViewController.callMethod), for:.touchUpInside)
button.frame = CGRect.init(x: 0, y: 0, width: 30, height: 30) //CGRectMake(0, 0, 30, 30)
let barButton = UIBarButtonItem.init(customView: button)
            self.navigationItem.leftBarButtonItem = barButton

Swift 4

let button = UIButton(type: UIButton.ButtonType.custom)
button.setImage(UIImage(named: "getstarted"), for: .normal)
button.addTarget(self, action:#selector(callMethod), for: .touchDragInside)
button.frame = CGRect(x: 0, y: 0, width: 30, height: 30)
let barButton = UIBarButtonItem(customView: button)
self.navigationItem.leftBarButtonItems = [barButton]

Here is action

@objc func callMethod() {   
    //do stuff here
 }

Swift 5, XCode 11 to make Navigation Bar Item with rounded image, image from assets or to download from URL.

1) New file: UIBarButtonItem+RoundedView.swift

import Foundation

class ImageBarButton : UIView {
    var imageView: UIImageView!
    var button: UIButton!

    convenience init(withUrl imageURL: URL? = nil, withImage image: UIImage? = nil, frame: CGRect = CGRect(x: 0, y: 0, width: 40, height: 40)) {
        self.init(frame: frame)

        imageView = UIImageView(frame: frame)
        imageView.backgroundColor = .white
        imageView.layer.cornerRadius = frame.height/2
        imageView.clipsToBounds = true
        imageView.contentMode = .scaleAspectFill
        imageView.clipsToBounds = true
        addSubview(imageView)

        button = UIButton(frame: frame)
        button.backgroundColor = .clear
        button.setTitle("", for: .normal)
        addSubview(button)

        if let url = imageURL { // you can use pods like Nuke or Kingfisher 
         URLSession(configuration: .default).dataTask(with: URL(string: imageUrl)!) {[weak self] (data, response, error) in
          if let data = data , let image = UIImage(data: data) {
              DispatchQueue.main.async {
                self?.imgView.image = image
              }
           }
         }.resume()
        } else if let image = image {
            self.imageView.image = image
        }
    }

    func load()-> UIBarButtonItem {
        return UIBarButtonItem(customView: self)
    }
}

2) Add navigation bar items, you can use navigationItem.rightBarButtonItems, navigationItem.leftBarButtonItems:

private func initalizeNavigationBarItems() {
    let searchBarButtonView = ImageBarButton(withImage: #imageLiteral(resourceName: "greenSearchIcon")) // Assets
    searchBarButtonView.button.addTarget(self, action: #selector(presentSearchViewController), for: .touchUpInside)

    if let user = AccountManager.currentUser, let userProfilePictureURL = user.imageUrl { // API Url
        let profileBarButtonView = ImageBarButton(withUrl: userProfilePictureURL)
        profileBarButtonView.button.addTarget(self, action: #selector(presentMoreViewController), for: .touchUpInside)
        navigationItem.rightBarButtonItems = [searchBarButtonView.load(), profileBarButtonView.load()]
    } else {
        let profileBarButtonView = ImageBarButton(withImage: #imageLiteral(resourceName: "profileIcon"))
        profileBarButtonView.button.addTarget(self, action: #selector(presentMoreViewController), for: .touchUpInside)
        navigationItem.rightBarButtonItems = [searchBarButtonView.load(), profileBarButtonView.load()]
    }
}

@objc func presentMoreViewController(_ sender: Any) {
    // present MoreViewController
}

@objc func presentSearchViewController(_ sender: Any) {
    // present SearchViewController
}

Preview

Use this code:

self.navigationItem.leftBarButtonItem = nil

let button = UIButton(type: .custom)
button.setImage(UIImage (named: "ChatTab"), for: .normal)
button.frame = CGRect(x: 0.0, y: 0.0, width: 35.0, height: 35.0)
//button.addTarget(target, action: nil, for: .touchUpInside)
let barButtonItem = UIBarButtonItem(customView: button)

let button2 = UIButton(type: .custom)
button2.setImage(UIImage (named: "ActivityTab"), for: .normal)
button2.frame = CGRect(x: 0.0, y: 0.0, width: 35.0, height: 35.0)
//button.addTarget(target, action: nil, for: .touchUpInside)

let barButtonItem2 = UIBarButtonItem(customView: button2)
self.navigationItem.rightBarButtonItems = [barButtonItem, barButtonItem2]

Output: