Extract HTML from Android webview

Having a webview in android and wanting to fiddle with the HTML?

Injecting javascript in android webview

Its easy, make sure you have javascript enabled and simply load url containing javascript:

mBrowser = new WebView(context);
mBrowser.getSettings().setJavaScriptEnabled(true);
mBrowser.loadUrl("javascript:getElementById('ad_container').style.display='none');");

In most cases, you first want to load the actual web page, then inject the javascript - this is done by using a WebViewClient which overrides onPageFinished.

mBrowser.setWebViewClient(new WebViewClient() {
   @Override
   public void onPageFinished(WebView view, String url) {
      // check url
      if (SOME_WEBPAGE.equals(url) {
        loadUrl(JAVASCRIPT_CODE);
      }
   }
});
mBrowser.loadUrl(SOME_WEBPAGE);

Extracting HTML from Android webview

Taking it one step further - let's get HTML from a page and use it in our program. This is accomplished by using a JavascriptInterface with our webview.

mBrowser.getSettings().setJavaScriptEnabled();
// add javascript interface with example method
mBrowser.addJavaScriptInterface(new JavaScriptInterface() {
   public void setTitle(String html) {
      mTitle = html;
   }
}, "MY_JS");
// add webview client that calls javascript interface when page is loaded
mBrowser.addWebViewClient(new WebViewClient() {
   @Override
   public void onPageFinished(WebView view, String url) {
       view.loadUrl("javascript:window.MY_JS.setTitle(document.getElementsByTagName('title')[0].innerHTML);");
   }

mBrowser.loadUrl(SOME_WEBPAGE);

That's it - using the combination of WebVievClient and JavascriptInterface is very powerful - drawback is that I have not found an easy way of debugging javascript - if your javascript fails it will fail silent.

Nice thing is you can test your javascript on Firefox using Firebug on your main computer before adding code to your android project.