加载本地资源时 UIWebView 和 WKWebView 有什么区别 [英] What's the difference between UIWebView and WKWebView when loading local resources

问题描述

我想用 webView 加载本地资源.我用 UIWebView 和 WKWebView 构建了一个演示，用下面的代码做一些测试.

 let uiWebView = UIWebView(frame: self.view.bounds)self.view.addSubview(uiWebView)让 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")守卫让 realPath = path else {返回}让 url = URL(string: realPath)让 fileUrl = URL(fileURLWithPath: realPath)如果让 realUrl = url {uiWebView.loadRequest(URLRequest(url:realUrl))wkWebView.load(URLRequest(url:realUrl))}//uiWebView.loadRequest(URLRequest(url:fileUrl))//wkWebView.load(URLRequest(url:fileUrl))

uiWebView 可以加载资源但 wkWebView 不能.但是如果我使用

 uiWebView.loadRequest(URLRequest(url:fileUrl))wkWebView.load(URLRequest(url:fileUrl))

uiWebView 和 wkWebView 都可以很好地工作.我很困惑，谁能为我解释一下:我不应该对本地资源使用 URL(string: realPath) 吗?但是为什么 UIWebView 可以使用呢?

解决方案

几点:

1. Apple 建议您在 iOS 8 中使用 WKWebview然后.我会避免使用 UIWebView 编写新代码.

<块引用>

在 iOS 8 及更高版本中运行的应用程序中，使用 WKWebView 类而不是使用 UIWebView.此外，如果您呈现不应运行 JavaScript 的文件，请考虑将 WKPreferences 属性 javaScriptEnabled 设置为 false.

2. Apple 一直试图摆脱 path，而是希望使用 URI 甚至本地文件.他们建议您不要使用 /path/to/file.png 而是使用 file:///path/to/file.png .

至于为什么一个 URL 有效而另一个无效，让我们举一个最小的例子:

let realPath = "/path/to/file.png"让 url = URL(string: realPath)///path/to/file.png让 fileUrl = URL(fileURLWithPath: realPath)//file:///path/to/file.png

• url 不提供方案(又名协议).它只能与另一个 URL 结合使用，以提供您尝试访问的资源的绝对地址.UIWebView 出于向后兼容的原因支持它，但 Apple 决定从 WKWebView 开始.
• fileURL 有一个方案 (file://)，它告诉资源位于本地文件系统上.其他常见方案有 http、https、ftp 等.它是资源的完整地址，因此两个视图都知道如何解析它.

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.

    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))

The uiWebView can load the resource but wkWebView can not. But if I use

  uiWebView.loadRequest(URLRequest(url:fileUrl))
  wkWebView.load(URLRequest(url:fileUrl))

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 ?

解决方案

A couple points:

1. Apple recommends that you use WKWebview for iOS 8 and later. I would avoid writing new code with UIWebView.

In apps that run in iOS 8 and later, use the WKWebView class instead of using UIWebView. Additionally, consider setting the WKPreferences property javaScriptEnabled to false if you render files that are not supposed to run JavaScript.

2. Apple has been trying to move away from path and instead wants to use URI even for local files. They recommend that you NOT use /path/to/file.png and use file:///path/to/file.png instead.

As to why one URL works and the other does not, let's make a minimal example:

let realPath = "/path/to/file.png"
let url = URL(string: realPath)               // /path/to/file.png
let fileUrl = URL(fileURLWithPath: realPath)  // file:///path/to/file.png

• url does not provide the scheme (a.k.a protocol). It should only be used in conjunction with another URL to give the absolute address of the resource you are trying to reach. UIWebView supports it for backwards-compatibility reasons but Apple decided to start clean with WKWebView.
• fileURL has a scheme (file://) that tells the resource is located on the local file system. Other common schemes are http, https, ftp, etc. It's a complete address to a resource so both views know how to resolve it.

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