Using JavaScriptInterface to return page elements

Question

I have a simple WebViewClient class that should return all the <p> elements of the page I am currently on (in a webview)

Here is the code

public class SearchClient extends WebViewClient {

class MyJavaScriptInterface {
    @SuppressWarnings("unused")
    public void processHTML(String[] html) {
    Log.w("Length", String.valueOf(html.length));
        for(String s : html)
        {

            Log.w("Row", s.toString());
        }



    }
}


public SearchClient(WebView wv)
{
    wv.addJavascriptInterface(new MyJavaScriptInterface(), "HTMLOUT");
}

public void onPageFinished(WebView view, String url) {
    view.loadUrl("javascript:window.HTMLOUT.processHTML(document.getElementsByTagName('p'));");

}

}

document.getElementsByTagName clearly is returning the elements because "Log.w" line in the processHTML function has over 100 strings ... but the for loop crashes. Why is this??

Answer 1

NodeList is a JavaScript class, but only a Java interface. In JavaScript you should create a method that converts the list to and array of Strings then you can pass it into your JavaScriptInterface method.

From this SO question a solution could be:

function toArray(obj) {
  var array = [];
  // iterate backwards ensuring that length is an UInt32
  for (var i = obj.length >>> 0; i--;) { 
  array[i] = obj[i];
  }
  return array;
} 

It is also possible this would work (from question in link above), but have not tested myself:

Array.prototype.slice.call(list,0)