I tried both of the following
webviewurl = "https://drive.google.com/viewerng/viewer?embedded=true&url=" + webviewurl;
webviewurl = "https://docs.google.com/gview?embedded=true&url=" + webviewurl;
But not useful...my code is like this...
mWebview.getSettings().setJavaScriptEnabled(true);
if(webviewurl.contains(".pdf")){
webviewurl = "https://docs.google.com/gview?embedded=true&url="+ webviewurl;
mWebview.loadUrl(webviewurl);
}else{
mWebview.loadUrl(iattach);
}