webview.swift

import UIKit
import WebKit
class WebVController: UIViewController {
    @IBOutlet weak var viewForWeb: UIView!
    @IBOutlet weak var activityIndicatorView: UIActivityIndicatorView!
    fileprivate var webView:WKWebView?
    fileprivate var btnBack = UIBarButtonItem()
    var urlString:String? = nil
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setWKWebView()
    }
    
    deinit {
        urlString = nil
        webView = nil
        //        print("WebVC deinit.")
    }
    fileprivate func setWKWebView(){
        if (urlString ?? "") != "" {
            if let _webUrl = urlString {
                webView = WKWebView(frame: self.viewForWeb.bounds)
                guard let webView = webView else { return }
                setWKWebviewConstraints()
                webView.navigationDelegate = self
                let url = URL (string: _webUrl)
                let request = URLRequest(url: url!)
                _ = webView.load(request)
                webView.scrollView.bounces = false//防止在頂端時往下拉的空白出現
//                webView?.autoresizingMask = [UIViewAutoresizing.flexibleWidth, UIViewAutoresizing.flexibleHeight]
            }
        } else {
            activityIndicatorView.isHidden = true
            view.addToBeSuppliedView()
        }
    }
    //MARK:- set webView constraints
    fileprivate func setWKWebviewConstraints(){
        guard let webView = webView else { return }
        webView.translatesAutoresizingMaskIntoConstraints = false
        let height = NSLayoutConstraint(item: webView, attribute: .height, relatedBy: .equal, toItem: viewForWeb, attribute: .height, multiplier: 1, constant: 0)
        let width = NSLayoutConstraint(item: webView, attribute: .width, relatedBy: .equal, toItem: viewForWeb, attribute: .width, multiplier: 1, constant: 0)
        viewForWeb.addConstraints([height, width])
    }
    
    //MARK:- check webView can not go back
    fileprivate func checkCanBack() {
        guard let webView = webView else { return }
        navigationItem.leftBarButtonItem?.isEnabled = webView.canGoBack
        setNavBar()
    }
    
    //MARK:- set navi bar left button
    fileprivate func setNavBar(){
        guard let webView = webView else { return }
        if webView.canGoBack {
            let back = UIBarButtonItem(image: UIImage(named: "icon-goleft"), style: .plain, target: self, action: #selector(backAction))
            navigationItem.leftBarButtonItem = back
        }else{
            navigationItem.setLeftBarButton(nil, animated: true)
        }
    }
    
    //MARK:- webView go back func
    @objc fileprivate func backAction() {
        guard let webView = webView else { return }
        if webView.canGoBack {
            webView.goBack()
        }
    }
}