title: What's the difference between UIWebView and WKWebView when loading local resources
body: <p>I want to load local resources with webView. I built a demo with both UIWebView and WKWebView to do some test with the code below.</p>
  
  <pre><code>    let uiWebView = UIWebView(frame: self.view.bounds)
      self.view.addSubview(uiWebView)
  
      let wkWebView = WKWebView(frame:CGRect(x: 0, y: 400, width: 500, height: 500))
      self.view.addSubview(wkWebView)
  
      let path = Bundle.main.path(forResource:"1", ofType: "png")
  
      guard let realPath = path else {
          return
      }
  
      let url = URL(string: realPath)
      let fileUrl = URL(fileURLWithPath: realPath)
  
      if let realUrl = url {
          uiWebView.loadRequest(URLRequest(url:realUrl))
          wkWebView.load(URLRequest(url:realUrl))
      }
  
  
    // uiWebView.loadRequest(URLRequest(url:fileUrl))
    // wkWebView.load(URLRequest(url:fileUrl))
  </code></pre>
  
  <p>The uiWebView can load the resource but wkWebView can not. But if I use</p>
  
  <pre><code>  uiWebView.loadRequest(URLRequest(url:fileUrl))
    wkWebView.load(URLRequest(url:fileUrl))
  </code></pre>
  
  <p>both uiWebView and wkWebView can work well.
  I am confused and can anyone explain that for me:
  Shouldn't I use URL(string: realPath) for a local resource? But why UIWebView can use it ? </p>