调用didFinishNavigation时，WKWebView尚未完成加载-WKWebView中的错误? [英] WKWebView didn't finish loading, when didFinishNavigation is called - Bug in WKWebView?

问题描述

目标:在网站加载完成后拍摄WKWebView的屏幕截图

Goal: To take a screenshot of WKWebView after the website finished loading

采用的方法:

• 在UIViewController中定义WKWebView变量

• 创建了一个名为screen capture()的扩展方法，该方法获取WKWebView的图像

• Defined a WKWebView var in UIViewController

• Created an extension method called screen capture() that takes image of WKWebView

使我的UIViewController实现WKNavigationDelegate

Made my UIViewController to implement WKNavigationDelegate

设置wkwebview.navigationDelegate = self(在UIViewController初始化中)

Set the wkwebview.navigationDelegate = self ( in the UIViewController init)

在UIViewcontroller中实现didFinishNavigation委托功能，以调用WKWebView的屏幕捕获扩展方法

Implemented the didFinishNavigation delegation func in UIViewcontroller to call screen capture extension method for WKWebView

func webView(webView: WKWebView, didFinishNavigation navigation: WKNavigation!) {
    let img = webView.screenCapture()
}

问题:

• 调试模拟器时，即使网站尚未在WKWebView中呈现，我仍注意到该控件到达了didFinishNavigation()函数.
• 相应地，所截取的图像截图为白色斑点.

我在这里想念什么?我查看了WKWebView的所有可能的委托函数，似乎没有其他东西代表WKWebView中内容加载的完成.如果能解决问题，将不胜感激

What am I missing here? I looked at all possible delegate functions for WKWebView and nothing else seem to represent the completion of content loading in WKWebView. Would appreciate help on if there is a work around

更新:添加我用来为网络视图拍摄屏幕截图的屏幕截图代码

Update: Adding screenshot code that I am using to take a screenshot for web view

class func captureEntireUIWebViewImage(webView: WKWebView) -> UIImage? {

    var webViewFrame = webView.scrollView.frame
    if (webView.scrollView.contentSize != CGSize(width: 0,height: 0)){
    webView.scrollView.frame = CGRectMake(webViewFrame.origin.x, webViewFrame.origin.y, webView.scrollView.contentSize.width, webView.scrollView.contentSize.height)

    UIGraphicsBeginImageContextWithOptions(webView.scrollView.contentSize, webView.scrollView.opaque, 0)
    webView.scrollView.layer.renderInContext(UIGraphicsGetCurrentContext())
     var image:UIImage = UIGraphicsGetImageFromCurrentImageContext()
     UIGraphicsEndImageContext()

     webView.scrollView.frame = webViewFrame         
     return image
    }

    return nil
 }

推荐答案

WKWebView不会使用委派来告知您内容加载完成的时间(这就是为什么找不到适合您目的的任何委托方法)的原因.知道WKWebView是否仍在加载的方法是使用KVO(键值观察)观察其loading属性.这样，当loading从true更改为false时，您会收到通知.

WKWebView doesn't use delegation to let you know when content loading is complete (that's why you can't find any delegate method that suits your purpose). The way to know whether a WKWebView is still loading is to use KVO (key-value observing) to watch its loading property. In this way, you receive a notification when loading changes from true to false.

这是一个循环的动画gif，显示了我测试时会发生的情况.我加载Web视图并通过KVO响应其loading属性以拍摄快照.上面的视图是Web视图；下部(压缩的)视图是快照.如您所见，快照确实捕获了加载的内容:

Here's a looping animated gif showing what happens when I test this. I load a web view and respond to its loading property through KVO to take a snapshot. The upper view is the web view; the lower (squashed) view is the snapshot. As you can see, the snapshot does capture the loaded content:

[NSTimer scheduledTimerWithTimeInterval:1.0 repeats:YES block:^(NSTimer * _Nonnull timer) {
    if (self->_webKitView.isLoading == true) {
        NSLog(@"Still loading...");
    }else {
        NSLog(@"Finished loading...");
        [timer invalidate];
        dispatch_async(dispatch_get_main_queue(), ^{
            [self->_activityIndicator stopAnimating];
        });
    }
}];

这篇关于调用didFinishNavigation时，WKWebView尚未完成加载-WKWebView中的错误?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！