Need help with threading a desktop alert

[DjangMan]

I've got an application that imports transactions into another system. As these transactions are imported I want to display a TJvDesktopAlert (from the Jedi library). What I found was that my program stopped while the alert was displayed and continued on when the alert vanished or was closed. So I figured this is a good time to look at a thread.

The idea was to spawn a thread that displays the alert. My main processing thread can continue and I don't really care about the alert after I spawn it.

The problem is that it doesn't seem to work - my main thread finishes importing transactions and then I get a long stack of alerts. It's as if the threads are waiting for something. I've included an Application.ProcessMessages in my loop but that didn't seem to help.

Here's my code:

   TMyAlertThread = class(TThread)
    protected
        procedure Execute; override;
    public
        Alert: TJvDesktopAlert;
        Shown: boolean;
        procedure ShowMe;
    end;

procedure TMyAlertThread.ShowMe;
begin
    if Assigned(Alert) then begin
        if not(Shown) then begin
            Alert.Execute;
            Shown := True;
        end;
    end;
end;

procedure TMyAlertThread.Execute;
begin
    FreeOnTerminate := True;
    Synchronize(ShowMe);
    while Alert.Showing and (not terminated) do;
end;

procedure TdmDB.ShowAlert(aHeader, aBody: string; aDuration: Cardinal = 5000);
var
    DA: TJvDesktopAlert;
    FOptions:TJvDesktopAlertOptions;
    AlertThread: TMyAlertThread;
begin

    AlertThread := TMyAlertThread.Create(True);
    AlertThread.Shown := False;

    FOptions := [];

    DA := TJvDesktopAlert.Create(nil);
    with DA do begin
        AutoFree := True;
        HeaderText := aHeader;
        MessageText := aBody;
        Font.Style := Font.Style - [fsBold];
        Include(FOptions,daoCanClose);
        DA.Options := FOptions;
        StyleHandler.DisplayDuration := 5000;
        Location.Position := dapBottomRight;
    end;

    AlertThread.Alert := DA;
    AlertThread.Resume;

end;

Called with:

dmDB.ShowAlert('Order imported','Order ID:'+aOrderID+' imported as: '+OrderNumber,2000);

 

[whosrdaddy]

you are violating rule #1 with threading:

Your background thread may not interact directly with the GUI!

rethink your GUI design, you want to alert the user, but you want to continue processing, right?
Then DONT show a modal dialog box as this will interrupt the main thread, search for an alternative way to alert the user...


/Daddy

-----------------------------------------------------
What You See Is What You Get
Never underestimate tha powah of tha google!

 

[DjangMan]

Hmmm - I must be doing something wrong. The demo for the TJvDesktopAlert allows me to create the alert and then I can call showmessage('Hello') and while the dialog is displayed the alert will fade out by itself.

 

[frank77]

The 'Synchronize' marshals the call back to the main thread so you are not really achieving anything by using a thread here.

You need to make the alert.Execute non-modal.

 

[DjangMan]

Thank you, Frank. I'll give that a go.