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Getting the HTML source from an Android WebView

 3 years ago
source link: http://blog.weinigel.se/2014/03/05/getting-html-source-from-android-webview.html
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Getting the HTML source from an Android WebView

Mar 5, 2014

On and off I’m working on writing an Atom/RSS feed reader for Android. The feed reader is using an Android WebView to display the contents of a feed and to be able to debug some issues I had I wanted to be able to view the HTML source for a page.

That’s should be simple I though, just do WebView.getData() and show it in a dialog. But no, there’s no method to get the HTML source from a WebView, so one has to jump through a lot of hoops to do that. Also the examples I found uses WebView.addJavaScriptInterface to do its job which is not such a good idea because addJavaScriptInterface has security problems and doesn’t even work on Android 2.3. And I do want my application to run on fairly old Android devices (I still use a Motorola Defy at work, I like the form factor and that it’s waterproof).

So after a bit of thinking I figured out an easier way of getting the source. There is a class called WebViewClient which among other things can be used to override what should happen when a follows a link in the WebView. This together with a bit of JavaScript can be used to get the source.

First, when initializing the WebView, tell it to use a custom WebViewClient:

 mWebView = (WebView) mView.findViewById(R.id.web);
 mWebView.setWebViewClient(new MyWebViewClient());

When asked to view the source, enable JavaScript for the WebView and then inject a bit of JavaScript which builds and follows an URL containing the HTML:

 public void viewSource() {
   mWebView.getSettings().setJavaScriptEnabled(true);
   mWebView.loadUrl(
     "javascript:this.document.location.href = 'source://' + encodeURI(document.documentElement.outerHTML);");
 }

The custom WebViewClient will catch this URL:

 public class MyWebViewClient extends WebViewClient {
     public boolean shouldOverrideUrlLoading(WebView view, String url) {
         if (url.startsWith("source://")) {
             try {
                 String html = URLDecoder.decode(url, "UTF-8").substring(9);
                 sourceReceived(html);
             } catch (UnsupportedEncodingException e) {
                 Log.e("example", "failed to decode source", e);
             }
             mWebView.getSettings().setJavaScriptEnabled(false);
             return true;
         }
         // For all other links, let the WebView do it's normal thing
         return false;
   }
 }

And we can finally show the source in a dialog:

 private void sourceReceived(String html) {
   AlertDialog.Builder builder = new AlertDialog.Builder(this);
   builder.setMessage(html);
   builder.setTitle("View Source");
   AlertDialog dialog = builder.create();
   dialog.show();
 }

As simple as that. And it seems to work on everything from Android 2.3 up to Android 4.4.

Although what we get from the WebView does not quite seem to be the source code it was fed to begin with. It seems that the WebView will fix up the HTML so that it is correct and will also decode any entitydefs. So for example if the WebView was fed “<p>Hello Wörld<p>” what we would get back is “<html><head></head><body><p>Hello Wörld<p></body></html>”. It’s still useful for what I wanted to do though.


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