blocks|key|4599359|text|对于使用Swift的iOS+10%2B：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4599360|self.webView+=+WKWebView()
self.webView!.isOpaque+=+false
self.webView!.backgroundColor+=+UIColor.clear
self.webView!.scrollView.backgroundColor+=+UIColor.clear|code-block|syntax|javascript|4599361|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

For iOS 10+ using Swift:

<pre><code>self.webView = WKWebView()
self.webView!.isOpaque = false
self.webView!.backgroundColor = UIColor.clear
self.webView!.scrollView.backgroundColor = UIColor.clear
</code></pre>

blocks|key|4599282|text|这段代码可能会对你有所帮助。针对Swift+3%2B进行了更新|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4599283|self.webView+=+WKWebView()
self.webView.isOpaque+=+false
self.webView.backgroundColor+=+UIColor.clear
self.webView.scrollView.backgroundColor+=+UIColor.clear|code-block|syntax|javascript|4599284|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This code might help you. Updated for Swift 3+

<pre><code>self.webView = WKWebView()
self.webView.isOpaque = false
self.webView.backgroundColor = UIColor.clear
self.webView.scrollView.backgroundColor = UIColor.clear
</code></pre>

blocks|key|93329|text|using+objective+c.
wkWebView.backgroundColor+=+[UIColor+clearColor];
wkWebView.scrollView.backgroundColor+=+[UIColor+clearColor];
wkWebView.opaque+=+false;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|93330|它将删除wkwebView中的白色背景色。|unstyled|93331|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>using objective c.
wkWebView.backgroundColor = [UIColor clearColor];
wkWebView.scrollView.backgroundColor = [UIColor clearColor];
wkWebView.opaque = false;
</code></pre>

It will remove the white background colour in wkwebView.

blocks|key|93094|text|这个bug似乎已经在Beta+5中修复了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|93095|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

This bug seems to be fixed in Beta 5.

blocks|key|93205|text|我知道这是一个非常古老的问题。但我今天一直在纠结这个问题。我不知道是不是只有我，但是webView.backgroundColor在WKWebView中是未定义的，并且webView.opaque是只读的。我解决这个问题的唯一方法是将web+views图层背景颜色设置为CGColor+clear|type|unstyled|depth|inlineStyleRanges|entityRanges|data|93206|webview.wantsLayer+=+true
webView.layer?.backgroundColor+=+NSColor.clearColor().CGColor|code-block|syntax|javascript|93207|和包含NSView以相同的方式|93208|webViewParent.layer?.backgroundColor+=+NSColor.clearColor().CGColor|93209|这是唯一对我有效的方法，我希望它也能帮助其他人。|93210|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I know this is a very old question. But I've been struggling with this today. I don't know if it's just me, but webView.backgroundColor was undefined in WKWebView, and webView.opaque was read-only. The only way for me to fix this was to set the web views layer background color to the CGColor clear

<pre><code>webview.wantsLayer = true
webView.layer?.backgroundColor = NSColor.clearColor().CGColor
</code></pre>

and the containing NSView the same way

<pre><code>webViewParent.layer?.backgroundColor = NSColor.clearColor().CGColor
</code></pre>

That's the only thing that worked for me, I hope it could help someone else as well.

blocks|key|4599244|text|下面的代码适用于我：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4599245|+[wkWebView+setValue:YES+forKey:@"drawsTransparentBackground"];|code-block|syntax|javascript|4599246|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Code below works for me:

<pre><code> [wkWebView setValue:YES forKey:@"drawsTransparentBackground"];
</code></pre>

blocks|key|93320|text|如果您正在加载PDF，并且想要一个不同于标准灰色的背景颜色，那么似乎有必要等到文档加载完成后，再清除子视图的背景。使用WKWebView而不是PDFView+(iOS+11%2B)的优点是，WKWebView具有双击缩放和内置的页数指示器，并且与较旧版本的iOS兼容。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|93321|应该注意的是，像这样挖掘系统视图并不是一个很好的实践，因为Apple可以随时更改实现，这可能会破坏解决方案。|93322|下面是我如何在Swift+4中实现一个黑色背景的PDF预览控制器：|93323|class+SomeViewController:+UIViewController+{

++++var+observer:+NSKeyValueObservation?
++++var+url:+URL

++++init(url:+URL)+{
++++++++self.url+=+url
++++++++super.init(nibName:+nil,+bundle:+nil)
++++}

++++func+viewDidLoad()+{
++++++++super.viewDidLoad()
++++++++self.view.backgroundColor+=+UIColor.black
++++++++let+webView+=+WKWebView()
++++++++webView.translatesAutoResizingMaskIntoConstraints+=+false
++++++++self.view.addSubview(webView)
++++++++NSLayoutConstraint.activate([
++++++++++++webView.topAnchor.constraint(equalTo:+self.view.topAnchor),
++++++++++++webView.leftAnchor.constraint(equalTo:+self.view.leftAnchor),
++++++++++++webView.rightAnchor.constraint(equalTo:+self.view.rightAnchor),
++++++++++++webView.bottomAnchor.constraint(equalTo:+self.view.bottomAnchor)
++++++++])

++++++++self.observer+=+webView.observe(\.isLoading,+changeHandler:+{+(webView,+change)+in
++++++++++++webView.clearBackgrounds()
++++++++})

++++++++webView.loadFileURL(self.url,+allowingReadAccessTo:+self.url)

++++}
}

extension+UIView+{
++++func+clearBackgrounds()+{
++++++++self.backgroundColor+=+UIColor.clear
++++++++for+subview+in+self.subviews+{
++++++++++++subview.clearBackgrounds()
++++++++}
++++}
}|code-block|syntax|javascript|93324|entityMap^0|1N|9|1Z|7|2L|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|Y|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|Z|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

If you're loading a PDF and want a background color different than the standard gray, it seems that it is necessary to wait until the document is loaded, then clear the backgrounds of the subviews. The advantage of using a <code>WKWebView</code> over a <code>PDFView</code> (iOS 11+) is that <code>WKWebView</code>s have double-tap to zoom and a page count indicator built in, and are compatible with older versions of iOS. 

It should be noted that it's not a great practice to dig into system views like this as Apple can change the implementation at any time, potentially breaking the solution.

Here is how I implemented a PDF preview controller with a black background in Swift 4:

<pre><code>class SomeViewController: UIViewController {

 var observer: NSKeyValueObservation?
 var url: URL

 init(url: URL) {
 self.url = url
 super.init(nibName: nil, bundle: nil)
 }

 func viewDidLoad() {
 super.viewDidLoad()
 self.view.backgroundColor = UIColor.black
 let webView = WKWebView()
 webView.translatesAutoResizingMaskIntoConstraints = false
 self.view.addSubview(webView)
 NSLayoutConstraint.activate([
 webView.topAnchor.constraint(equalTo: self.view.topAnchor),
 webView.leftAnchor.constraint(equalTo: self.view.leftAnchor),
 webView.rightAnchor.constraint(equalTo: self.view.rightAnchor),
 webView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
 ])

 self.observer = webView.observe(\.isLoading, changeHandler: { (webView, change) in
 webView.clearBackgrounds()
 })

 webView.loadFileURL(self.url, allowingReadAccessTo: self.url)

 }
}

extension UIView {
 func clearBackgrounds() {
 self.backgroundColor = UIColor.clear
 for subview in self.subviews {
 subview.clearBackgrounds()
 }
 }
}
</code></pre>

blocks|key|93060|text|我还没有使用WKWebView，但即使是UIWebView过去也有这个问题，解决方案是将html内容封装在下面这样的内容中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|93061|<body+style="background-color:transparent;"></body>|code-block|syntax|javascript|93062|希望能有所帮助。|93063|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Haven't worked with WKWebView yet but even UIWebView used to have this issue and the solution was to wrap the html content inside something like this:

<pre><code>&lt;body style="background-color:transparent;"&gt;&lt;/body&gt;
</code></pre>

Hope it helps.

blocks|key|4599474|text|我不知道它是否有帮助，但我使用了下面的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4599475|func+setBackgroundWhite(subviews:+[UIView])+{
++for+subview+in+subviews+{
++++subview.backgroundColor+=+.white
++++setBackgroundWhite(subviews:+subview.subviews)
++}
+}|code-block|syntax|javascript|4599476|这在子视图中进行递归调用，将背景设置为白色或其他颜色。|4599477|我在加载PDF文件、WKWebView和iOS+10%2B时使用了以下代码。|offset|length|style|CODE|4599478|entityMap^0|0|0|0|A|9|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@$K|U|L|V|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

I don't know if it can help, but i used this solution below: 

<pre><code>func setBackgroundWhite(subviews: [UIView]) {
 for subview in subviews {
 subview.backgroundColor = .white
 setBackgroundWhite(subviews: subview.subviews)
 }
 }
</code></pre>

This does recursive call inner in subviews, setting up the background to white, or another color.

I used this code when loading PDF files, <code>WKWebView</code> and iOS 10+

blocks|key|4599523|text|在我的例子中，我需要在样式中将背景颜色更改为透明，并从手机/模拟器手册中删除应用程序-它看起来WKWebView缓存HTML+/样式|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4599524|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

In my case I need to change background-color to transparent in Styles and delete an App from phone/simulator manualny - it looks that WKWebView Cache HTML / Styles

In my app I wish to make the WKWebView with transparent background, so the view behind (an ImageView) can show through as background picture.

<pre><code> webView!.opaque = false
 webView!.backgroundColor = UIColor.clearColor()
</code></pre>

The code above works fine with UIWebView, but if webView is WKWebView, a white background will be shown.

Also tried putting transparent background color in CSS. The result is the same, only works in UIWebView but not WKWebView. Any suggestion?

Transparent background for WKWebView

在我的应用程序中，我希望使WKWebView具有透明的背景，以便后面的视图(一个ImageView)可以显示为背景图片。    webView!.opaque = false    webView!.backgroundColor = UIColor.clearColor()上面的代码可以很好地用于UIWebView，但如果webView为WKWebView，则会显示白色背景。我也尝试了在CSS中

问WKWebView的透明背景
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