아래와 같이 했는데 프로그세스바가 나타나지를 않네요

뭔가가 잘못됏나요?

this.getWindow().requestFeature(Window.FEATURE_PROGRESS);  
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
Activity activity = this;

  mainWebView.getSettings().setJavaScriptEnabled(true);
  mainWebView.getSettings().setSupportMultipleWindows(true);
  mainWebView.setHorizontalScrollBarEnabled(true);
  mainWebView.setVerticalScrollBarEnabled(true);
  mainWebView.getSettings().setDomStorageEnabled(true);
  mainWebView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
  mainWebView.setWebChromeClient(new webChromeClient());

    public class webChromeClient extends WebChromeClient {

  @Override
  public void onProgressChanged(WebView view, int progress) {
   // TODO Auto-generated method stub
   super.onProgressChanged(view, progress);
   activity.setProgress(progress * 100);
   //mPbProgress.setProgress(progress);
  }
 }