即使对于没有任何 Javascript 的网页，Javascript 注入也应该起作用吗？
我的应用程序中的方法之一是使用 此线程在渲染后捕获网页的整个 HTML：
// This call inject JavaScript into the page which just finished rendering.
browser.loadUrl(
"javascript:window.HTMLOUT.processHTML(
document.getElementsByTagName('html')[0].innerHTML);");
它可以工作——即使对于非常丰富的网页——但是当它尝试以相同的方式处理没有 任何 Javascript 的页面，它会生成以下错误：
ERROR/Web Console(1335): Uncaught TypeError:
Cannot call method 'processHTML' of undefined at :1
在我搜索可能的根本原因或解释时，我发现了很多描述 的帖子未捕获的类型错误：无法调用未定义的方法 *** at :1 有两个典型答案：
- 使用 webView.getSettings().setDomStorageEnabled(true);
- "通常，当错误的形式为 Cannot call method 'X' of 未定义，这意味着您尝试调用的任何对象X from 不存在。”
好吧，在我的例子中，问题的原因不能是 #1 (setDomStorageEnabled)，因为我已经正确设置了该设置在我的代码中！
所以唯一可能的解释是我尝试调用 processHTML() 的对象不存在，该对象名为 HTMLOUT 。在创建 WebView 对象并使用 setWebViewClient() 初始化它之后，在活动的 onCreate() 中创建：
webView.addJavascriptInterface(new JavascriptInterface(this, webView), "HTMLOUT");
这使我怀疑 JavascriptInterface 对象实例化由于某种原因失败，
这就是我的理解停止的地方 开始：
- 。我的问题 到目前为止我所描述的有道理吗？
- 如果是这样，为什么 JavascriptInterface 对象实例化会失败？
- 失败的原因是否可能是不存在？ 原始 HTML 中有任何 Javascript 吗？
- 可以采取什么措施来解决这个问题？
One of the methods in my applications is using the Javascript injection trick described in this thread to capture the entire HTML of a web page after rendering:
// This call inject JavaScript into the page which just finished rendering.
browser.loadUrl(
"javascript:window.HTMLOUT.processHTML(
document.getElementsByTagName('html')[0].innerHTML);");
It works -- even for very rich web pages -- but when it tries to handle in the same manner pages that do not have any Javascript in them, it generates the following error:
ERROR/Web Console(1335): Uncaught TypeError:
Cannot call method 'processHTML' of undefined at :1
In my search for possible root cause or explanation, I found quite a few postings describing an Uncaught TypeError: Cannot call method *** of undefined at :1 with two typical answers:
- Use webView.getSettings().setDomStorageEnabled(true);
- "Usually, when the error is of the form Cannot call method 'X' of
undefined, it means that whatever object you are attempting to call X from does not exist."
Well, the cause of the problem in my case cannot be #1 (setDomStorageEnabled), because I already have that set correctly in my code!
So the only other possible explanation is that the object from which I am trying to call processHTML() does not exits. That object is named HTMLOUT and it is created in the activity's onCreate(), after creating a WebView object and initializing it with setWebViewClient():
webView.addJavascriptInterface(new JavascriptInterface(this, webView), "HTMLOUT");
That leads me to suspect that the JavascriptInterface object instantiation fails for some reason.
This is where my understanding stops and my questions begin:
- Does what I have been describing so far make sense?
- If so, why would the JavascriptInterface object instantiation fail?
- Is it possible that the reason for the failure is the non-existence
of any Javascript in the original HTML? - What can be done to work around this problem?
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