Xcode 12.5及Swift 5+环境下WKWebView如何打开外部链接到Safari

现有代码的问题 #

• 未给WKWebView设置navigationDelegate，导致拦截跳转的代理方法无法触发
• 跳转拦截方法内部存在重复执行的逻辑冲突，分支判断和外部执行语句重复调用了打开链接和decisionHandler方法，会导致逻辑异常

修改步骤 #

1. 让当前ViewController遵守WKNavigationDelegate协议
2. 初始化WKWebView时绑定navigationDelegate
3. 清理拦截方法内的冗余逻辑，仅拦截http/https协议的外部跳转调用系统Safari打开，本地file协议的资源正常在WebView内加载

修正后完整代码 #

import UIKit
import WebKit
import PDFKit

// 遵守WKNavigationDelegate协议
class ViewController: UIViewController, WKUIDelegate, WKNavigationDelegate {
    
    var webView: WKWebView!
    
    override func loadView() {
        let webConfiguration = WKWebViewConfiguration()
        webView = WKWebView(frame: .zero, configuration: webConfiguration)
        webView.uiDelegate = self
        // 绑定navigationDelegate
        webView.navigationDelegate = self
        view = webView
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        
        guard let url = Bundle.main.url(forResource: "index", withExtension: "html", subdirectory: "www") else { return }
        webView.loadFileURL(url, allowingReadAccessTo: url.deletingLastPathComponent())
        let request = URLRequest(url: url)
        webView.load(request)
    }
    
    // WKNavigationDelegate 跳转拦截方法
    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
        // 仅拦截用户点击触发的链接跳转
        guard navigationAction.navigationType == .linkActivated,
              let url = navigationAction.request.url,
              let scheme = url.scheme else {
            decisionHandler(.allow)
            return
        }
        // 判断协议为http/https则跳系统Safari
        if scheme == "http" || scheme == "https" {
            UIApplication.shared.open(url)
            decisionHandler(.cancel)
            return
        }
        // 其他协议（比如本地的file协议）正常加载
        decisionHandler(.allow)
    }
}

说明 #

本地www文件夹内的资源使用file协议加载，不会被上述拦截逻辑命中，会正常在WebView内渲染，只有用户点击的外部http/https链接会被拦截跳转到系统Safari打开。

内容的提问来源于stack exchange，提问作者ralphb