flexmdi handles a lot of the mundane tasks of an MDI interface for you: minimizing, maximizing, closing, etc. However, we also realize that the out of the box behavior will not always fit your exact needs. Consequently, one of our biggest architectural goals (and challenges) was how to provide enough default behavior that getting up and running was lightning fast while still allowing the fine grained control a truly useful project provides. I described the basic method we used in a previous post, but wanted to give an example more specific to flexmdi now that its live.

The example we always thought of during development was requiring a user to confirm that they want to close a window before it is actually removed, like this (view source enabled). Any listeners you set on MDIWindow or MDIManager will be called before the internal listeners that execute the default behavior. As long as you don't give your listener a negative priority that is, so don't do that if you want first dibs. To prevent the default behavior from executing, you simply call event.stopImmediatePropagation() on the event passed into your listener. If you might want to execute that default behavior in the future, such as after the user confirms they want to close the window, you need to store the event somewhere. Let's look at some sample code (assumes you're listening on the manager in order to catch events for all of the windows):

private function confirmWindowClose(event:Event):void
{
    if(event is MDIManagerEvent)
    {
        // this is the line that prevents the default behavior from executing as usual
        event.stopImmediatePropagation();
        // store the event in case we want to resume later (user confirms their intention)
        queuedEvent = event as MDIManagerEvent;
        // ask user to confirm
        Alert.show("Seriously? Close it?", null, 3, null, handleAlertResponse);
    }
}

So now we have captured the event, put it off to the side and prompted the user to make sure they really really really want to close the window. handleAlertResponse() will be called when the user clicks on one of the buttons provided by our Alert. Here is what that method looks like:

// if the user said yes, we execute the default behavior of playing an effect
// and then removing the window by calling the appropriately named executeDefaultBehavior() method
private function handleAlertResponse(event:CloseEvent):void
{
    if(event.detail == mx.controls.Alert.YES)
    {
        mdiCanvas.windowManager.executeDefaultBehavior(queuedEvent);
    }
}

As you can see, if the user told us to do so we go ahead and "resume" the default behavior (playing an effect and removing the window) by calling MDIManager.executeDefaultBehavior() and passing it the event we previously stored. Thats it. You now have an MDI interface that requires confirmation when closing windows.

Because executeDefaultBehavior() contains a switch that examines the event's type, you can use this exact approach to prevent and/or modify default behaviors for any event flexmdi uses. I think confirming window close would definitely be the most common usage, but I'm sure its not the only one. For example, you could intercept the windowMaximize event and fade all other windows back or minimize all other windows before animating the window to its maximized size/position.

As always, questions, comments, complaints, etc are welcome. I would love to get feedback on this and hear if you think its easy enough/will suit your needs/could be improved/will end world hunger.