Android Web Scraping with a Headless Browser

Ok after 2 weeks I admit defeat and are using a workaround which works great for me at the moment.

The problem:

It is too difficult to port HTMLUnit to Android (or at least with my level of expertise). I am sure its a worthwhile project (and not that time consuming for experienced java programmer) . I emailed the guys at HTMLUnit and they commented that they are not looking into a port or what effort will be involved but suggested anyone who wants to start with such a project should send an message to their mailing list to get more developers involved (http://htmlunit.sourceforge.net/mail-lists.html).

The workaround:

I used android's built in WebView and overrided the onPageFinished method of Webview class to inject Javascript that grabs all the html after the page has fully loaded. Webview can also be used to called futher javascript actions, clicking buttons, filling in forms etc.

Code:

webView.getSettings().setJavaScriptEnabled(true);
MyJavaScriptInterface jInterface = new MyJavaScriptInterface();
webView.addJavascriptInterface(jInterface, "HtmlViewer");

webView.setWebViewClient(new WebViewClient() {

    @Override
    public void onPageFinished(WebView view, String url) {
       //Load HTML
       webView.loadUrl("javascript:window.HtmlViewer.showHTML('<html>'+document.getElementsByTagName('html')[0].innerHTML+'</html>');");
    }

}

webView.loadUrl(StartURL);
ParseHtml(jInterface.html);   

public class MyJavaScriptInterface {

    public String html;

    @JavascriptInterface
    public void showHTML(String _html) {
        html = _html;
    }
}

Scrape a dynamically-produced page on Android

Selenium would be a good option for web scraping. https://www.selenium.dev/ It basically has access to the website's DOM. In past experience, a dynamically generated web page can be difficult to scrape. RegExp will be your friend. https://regexone.com/

Selendroid as a web scraper

Unfortunately I didn't get Selendroid to work. But I find a workaround to scrape dynamic content by using just Android's built in WebView with JavaScript enabled.

mWebView = new WebView();
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.addJavascriptInterface(new HtmlHandler(), "HtmlHandler");

mWebView.setWebViewClient(new WebViewClient() {
   @Override
   public void onPageFinished(WebView view, String url) {
       super.onPageFinished(view, url);

       if (url == urlToLoad) {
       // Pass html source to the HtmlHandler
       WebView.loadUrl("javascript:HtmlHandler.handleHtml(document.documentElement.outerHTML);");

   }
});

The JS method document.documentElement.outerHTML will retrieve the full html contained in the loaded url. Then the retrived html string is sent to handleHtml method in HtmlHandler class.

class HtmlHandler {
        @JavascriptInterface
        @SuppressWarnings("unused")
        public void handleHtml(String html) {
            // scrape the content here

        }
    }

You may use a library like Jsoup to scrape the necessary content from the html String.

Android Web Scraping with a Headless Browser