ASP.NET AJAX: Rendering a Gmail-like 'Loading' Indicator over a Specific ASP.NET Control
I came across a blog post discussing a slick way to use the ASP.NET AJAX UpdateProgress control to add a gmail-like progress indicator to an ASP.NET web page.
I liked the approach the author used and it clearly works great for scenarios where you want to display a single 'something is happening' message to the user while the page is being updated. However, after the operation completes and the indicator disappears, it is still up to the user to figure out where on the screen (i.e. what control was updated?) to look for the new changes. If your screens are relatively simple, or if you feel the update should be obvious this is probably not an issue for you. Unfortunately things aren't so for the web application I am currently working on. A few of the screens contain a number of different sections and users would like to see the indicator rendered over the control (most commonly a GridView or DetailsView) that is being updated.
To achieve this, I am using the UpdatePanelAnimationExtender control that is part of the AjaxControlToolkit (You can follow directions here to install and get started using the toolkit). This control allows for defining the visual effects you want run before (the OnUpdating animation) and after (the OnUpdated animation) the contents within the UpdatePanel have been refreshed. For the gmail progress indicator, the OnUpdaing animation runs a piece of JavaScript that calculates the bounds of the GridView that is contained within the UpdatePanel and renders an HTML DIV in the upper right hand corner of the GridView control. After the update occurs, the OnUpdated fires and runs another piece of JavaScript that hides the DIV.
You can view a live demo here and download the sample web application with all of the code included here. There is no code-behind for the page, so if you are intereseted in quickly viewing the markup and JavaScript for the page - it is posted below (you will have to change the connection string to point to your copy of the Northwind database ...)
Code sample for this page:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>Untitled Page</title>
<script type="text/javascript" language="javascript">
function onUpdating(){
// get the update progress div
var updateProgressDiv = $get('updateProgressDiv');
// get the gridview element
var gridView = $get('<%= this.gvCustomers.ClientID %>');
// make it visible
updateProgressDiv.style.display = '';
// get the bounds of both the gridview and the progress div
var gridViewBounds = Sys.UI.DomElement.getBounds(gridView);
var updateProgressDivBounds = Sys.UI.DomElement.getBounds(updateProgressDiv);
var x;
var y;
// do the math to figure out where to position the element
if($get('rdoCenter').checked){
// center of gridview
x = gridViewBounds.x + Math.round(gridViewBounds.width / 2) - Math.round(updateProgressDivBounds.width / 2);
y = gridViewBounds.y + Math.round(gridViewBounds.height / 2) - Math.round(updateProgressDivBounds.height / 2);
}
else if($get('rdoTopLeft').checked){
// top left of gridview
x = gridViewBounds.x;
y = gridViewBounds.y;
}
else{
// top right of gridview
x = (gridViewBounds.x + gridViewBounds.width - updateProgressDivBounds.width);
y = gridViewBounds.y;
}
// set the progress element to this position
Sys.UI.DomElement.setLocation (updateProgressDiv, x, y);
}
function onUpdated() {
// get the update progress div
var updateProgressDiv = $get('updateProgressDiv');
// make it invisible
updateProgressDiv.style.display = 'none';
}
</script>
</head>
<body>
<form id="form" runat="server">
<asp:ScriptManager ID="scriptManager" runat="server" />
<div>
<asp:SqlDataSource ID="sqldsCustomers" runat="server"
SelectCommand="select customerid, companyname, contactname, contacttitle from dbo.customers"
SelectCommandType="Text" ConnectionString="todo" />
<p style="background-color:AliceBlue; width:95%">
Example of using an UpdatePanelAnimationExtender to place an animated gif over a GridView while the<br />
GridView is being refreshed. Click the column headers or the paging buttons to cause the grid to refresh<br />
You can toggle where the animation is to be displayed using the radio buttons<br />
</p>
<div>
<input id="rdoCenter" type="radio" name="location" value="center" checked="checked" />Center
<input id="rdoTopLeft" type="radio" name="location" value="topleft" />Top Left
<input id="rdoTopRight" type="radio" name="location" value="topright" />Top Right
</div>
<br />
<br />
<asp:Label ID="lblTitle" runat="server" Text="Customers" BackColor="lightblue" Width="95%" />
<asp:UpdatePanel ID="updatePanel" runat="server">
<ContentTemplate>
<asp:GridView ID="gvCustomers" runat="server" AllowPaging="true" AllowSorting="true"
PageSize="20" DataSourceID="sqldsCustomers" Width="95%">
<AlternatingRowStyle BackColor="aliceBlue" />
<HeaderStyle HorizontalAlign="Left" />
</asp:GridView>
</ContentTemplate>
</asp:UpdatePanel>
<ajaxToolkit:UpdatePanelAnimationExtender ID="upae" BehaviorID="animation" runat="server" TargetControlID="updatePanel">
<Animations>
<OnUpdating>
<Parallel duration="0">
<%-- place the update progress div over the gridview control --%>
<ScriptAction Script="onUpdating();" />
</Parallel>
</OnUpdating>
<OnUpdated>
<Parallel duration="0">
<%--find the update progress div and place it over the gridview control--%>
<ScriptAction Script="onUpdated();" />
</Parallel>
</OnUpdated>
</Animations>
</ajaxToolkit:UpdatePanelAnimationExtender>
<div id="updateProgressDiv" style="background-color:#CF4342; display:none; position:absolute;">
<span style="color:#fff; margin:3px">Loading ...</span>
</div>
</div>
</form>
</body>