Sometimes throws Uncaught Error: Error calling method on NPObject on Android

Question

I am having problems with the Webview in Android and it's JavascriptInterfaces.

I am passing a string to the JavascriptInterface. When debugging it, I receive the correct string within my Android application. The problem: Sometimes I get an Uncaught Error: Error calling method on NPObject.

Does anybody know why?

The Interface in Java:

public class JSInterfaceGame extends JSInterface {

@JavascriptInterface
public void setShareText(String share){
    shareText = share;
    if(mJSInterfaceListener != null)
        mJSInterfaceListener.onParametersChanged(SHARE_TEXT);
}

The initialization in the onCreateView-Method within the Fragment:

online = (WebView) rootView.findViewById(R.id.online);
online.setWebViewClient(new WISWebviewClient() {
  @Override
  public void onStatusChanged(final WebView view, int progress, long duration) {
    //unrelated
  }
});

WebSettings ws = online.getSettings();
ws.setJavaScriptEnabled(true);
ws.setUserAgentString(USER_AGENT);
ws.setCacheMode(WebSettings.LOAD_DEFAULT);
ws.setRenderPriority(WebSettings.RenderPriority.HIGH);

SharedPreferences settings = getActivity().getSharedPreferences(GameActivity.PREFERENCES, Context.MODE_PRIVATE);

mJSInterface = new JSInterfaceGame();
mJSInterface.setJSInterfaceListener(this); // Defined elsewhere in this class.
mJSInterface.setPlayerName(settings.getString(GameActivity.PREFS_PlAYERNAME, null));
online.addJavascriptInterface(mJSInterface, "JSInterface");
online.loadUrl("http://myurl.something");

Call in Javascript:

function makeShareText() {
  var text = "Some text";
  console.log(typeof text); // Always a string.
  JSInterface.setShareText(text);
}

Answer 1

It happens when you try, using method called from javascript interface, to interact with UI. To solved it in this way:

class mJSInterface()
{

public void myFunction()
{
    runOnUiThread(new Runnable() {

            public void run() {
                //Code that interact with UI
            }
        });

    }

}