zoom control in webview.

Question

how can i prevent zoom controls in webview from disappearing after zooming in or out.

and these zoom controls always show up after sliding the webview i.e. zoom controls do not show up autmatically as soon as webview loads up.

i have tried this code.

webview = (WebView)findViewById(R.id.webview); //getWindow().requestFeature(Window.FEATURE_PROGRESS);

     WebSettings webSettings = webview.getSettings(); 
    webSettings.setJavaScriptEnabled(true); 
     webSettings.setLoadsImagesAutomatically(true);
      webSettings.setSupportZoom(true) ;
     webSettings.setBuiltInZoomControls(true);
    // findViewById(R.id.LinearLayout01).;



     webview.invokeZoomPicker();