R – Tips for implementing a ‘Please wait’ control for a Flex application

apache-flexpleasewaitweb services

What would be a clever way to make a 'please wait' control for a Flex application for long running operations like calling a webservice.

I am not asking about the graphical portion of it – just the 'controller' part. How should I trigger it and hide it. I am planning to make just a simple canvas with text in.

For instance :

  • can I somehow intercept all web service calls – and not have to activate it for every web service
  • how should i add it to my canvas. should it be added to 'stage' as a top level component?
  • should it have a 'cancel' button to cancel the web service request if it takes too long. that sounds kind of complicated because I'm not even sure if I can terminate a running async web request?

FYI: This is for a reporting application so long running queries are to be expected

Best Answer

One way I have done it in the past is to have a global integer and increment / decrement the value based on the web services running. When the counter was 0, I would hide the loading text, when it was greater than 0, I would display the loading text. Here is a simplified version of it:


<mx:Application>
    <mx:Script>
        [Bindable]public var ws_count:int = 0;
    </mx:Script>
    <mx:Label text = "loading..." visible="{ws_count > 0}" />
</mx:Application>

I then had a little helper class to control the global counter:


package ws {
    import mx.core.Application;
    public class WSCounter {
        public static function sent():void {
            Application.application.ws_count += 1;
        }
        public static function receive():void {
            Application.application.ws_count -= 1;
        }
    }
}

Then all that needs to be done is to call the helper function when a web service is called...e.g:


import ws.WSCounter;
import mx.rpc.http.HTTPService;

var srv:HTTPService = new HTTPService();
srv.url = "http://localhost/service.py";
srv.addEventListener(ResultEvent.RESULT,function(event:ResultEvent):void {
    WSCounter.receive();
});
srv.send();
WSCounter.sent();

I always have thought there was a better way to do this, like you said have some type of hook to detect if a service is running...I'm looking forward to other responses in this post...

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