ASP.NET HoverMenuExtender Lazy Download
I am trying to get my hovermenuextenders to do some kind of lazy loading. I have avatars all over the site that, when hovering, should discard different things (images, recent posts, number of posts, etc.). For obvious reasons, I don't want to do this for all the avatars on page_load.
Using the following code, I can get the hover event to trigger the postback to the server asynchronously (the breakpoint is put into onmouseover mode). However, the commands in the postback do not seem to be reflected after execution completes. The loaded image / label remains on the hover bar. Any help is appreciated!
EDIT . I just figured out that the last avatar displayed on the page is working correctly, but none of the above. Any ideas what might be causing this strange behavior?
<script language="javascript" type="text/javascript">
function OnHover(image) {
__doPostBack('<%= this.imageHoverTrigger.UniqueID %>', '');
}
</script>
<!-- DUMMY Hover Trigger -->
<input id="imageHoverTrigger" runat="server" style="display:none;"
type="button" onserverclick="imageHoverTrigger_Click" />
<!-- User Avatar -->
<div style="border: solid 1px #AAA; padding:2px; background-color:#fff;">
<asp:ImageButton ID="UserImg" runat="server" />
</div>
<!-- Hover tooltip disabled by default
(Explicitly enabled if needed)-->
<ajax:HoverMenuExtender ID="UserInfoHoverMenu" Enabled="false" runat="server"
OffsetX="-1"
OffsetY="3"
TargetControlID="UserImg"
PopupControlID="UserInfoPanel" dyn
HoverCssClass="userInfoHover"
PopupPosition="Bottom">
</ajax:HoverMenuExtender>
<!-- User Profile Info -->
<asp:Panel ID="UserInfoHover" runat="server" CssClass="userInfoPopupMenu">
<asp:UpdatePanel ID="UserInfoUpdatePanel" runat="server" UpdateMode="Conditional" >
<ContentTemplate>
<asp:Image ID="loadingImg" runat="server" ImageUrl="~/Design/images/ajax-loader-transp.gif" />
<asp:Label ID="loadingLbl" runat="server" Text="LOADING..." ></asp:Label>
<asp:Panel ID="UserInfo" runat="server" Visible="false">
<b><asp:Label ID="UserNameLbl" runat="server"></asp:Label><br /></b>
<span style="font-size:.8em">
<asp:Label ID="UserCityLbl" runat="server" Visible="false"></asp:Label> <asp:Label ID="UserStateLbl" runat="server" Visible="false"></asp:Label>
</span>
</asp:Panel>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="imageHoverTrigger" />
</Triggers>
</asp:UpdatePanel>
</asp:Panel>
And the code:
protected void Page_Load(object sender, EventArgs e)
{
UserImg.Attributes.Add("onmouseover", "javascript:OnHover(this)");
}
protected void imageHoverTrigger_Click(object sender, EventArgs args)
{
// Hide loading image/label
loadingLbl.Visible = false;
loadingImg.Visible = false;
//TODO: Set user data here
UserInfo.Visible = true;
}
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It revealed:
My link to the Page_Load page should have been:
UserImg.Attributes.Add("onmouseover", "javascript:OnHover('" + this.imageHoverTrigger.UniqueID + "','" + this.hiddenLbl.ClientID + "')");
UserImg.Attributes.Add("onmouseout", "javascript:ClearTimer()");
and the javascript function should have been:
var hoverTimer;
// Called on the hover of the user image
function OnHover(trigger, hiddenTxt) {
var field = document.getElementById(hiddenTxt);
// Only post if this hover hasn't been done before
if (field == null || field.innerHTML == "false") {
hoverTimer = setTimeout(function() { ShowInfo(trigger) }, 500);
}
}
// Clears timeout onmouseout
function ClearTimer() {
clearTimeout(hoverTimer);
}
// Retrieves user info from server
function ShowInfo(trigger) {
__doPostBack(trigger, '');
}
I also added a hidden field on the form so that I know when the cursor was hovered over. The code behind sets the hidden field to true and my javascript checks the value of the hidden field every time it is executed. This stops the code from executing round visits every time the user hovers over the image.
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