btnSubscribed.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {


            AlertDialog.Builder dialog = new AlertDialog.Builder(PreviewLatestVideo.this);
            LayoutInflater inflater = (LayoutInflater) PreviewLatestVideo.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View viewWeb = inflater.inflate(R.layout.web_charging,null);
            dialog.setView(viewWeb);

            webView.setWebViewClient(new customWebViewClient());
            webView.setInitialScale(350);
            webView.loadUrl(url);

            dialog.setPositiveButton(R.string.done, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    finish();
                }
            });
            dialog.show();
        }

    });

private class customWebViewClient extends WebViewClient {
    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {
        swipeRefreshLayout.setRefreshing(true); // <- Here null object reference
    }

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String request) {
        view.loadUrl(request);
        return true;
    }

    @Override
    public void onPageFinished(WebView view, String url) {
        swipeRefreshLayout.setRefreshing(false);
    }
}