Flex 3: synchronously loading an xml file

问题

My question is very simple: In flex3, is there a way to load an xml file synchronously?

I know how to load asynchronously, using a load event. This may be useful, or may not. I just want to read the file, parse it, do what I have to do with it, and continue executing code.

I have a component that uses an xml file to store some configuration parameters. I need to read the file when the object is initialized. However, with the event model, I can't control when the file is loaded, so I must write code to "wait" for the code to load. This is just ridiculous, or is it me? I want code like this:

var foo:Foo = new Foo(); //This constructor should read the xml and initialize the object.
foo.doSomething(); //When I call this method the xml must be already handled.

I can handle the xml file on the event, and it works fine, but the event fires after the doSomething method.

I hope I have explained myself. I think this should be really easy, but it's driving me crazy. I don't want to write code to wait for the event unless it's really necessary. I feel all this should be just one line of code!

回答1:

It's not possible to load synchronously, flash is built for the web and you can never be sure how long a call takes. Air is different because that loads from the filesystem, and there are nowhere near the same amounts of delay there.

The cleanest solution would be to listen for the load to complete inside Foo and calling doSomething() from inside, this way your "outer" class won't need to bother at all.

If you do absolutely need to call foo.doSomething() from the outside, you can use the event system. Let your Foo class dispatch an event when it is done loading:

dispatchEvent(new Event(Event.COMPLETE, true));

To catch that you will need to listen for it like so:

foo.addEventListener(Event.COMPLETE, handleFooComplete);

And you event handler function should look like this:

private function handleFooComplete(e:Event):void{
    foo.doSomething();
}

However you choose to do it, you will need to listen for Event.COMPLETE on the loader. There's no getting around that.

回答2:

I will answer myself, however I'd still like to know if someone comes up with better ideas. Answers from dirkgently and Peter Miehle are both helpful but does not solve my actual problem.

It seems synchronous loading is just not possible. The loading could fail or take too long, and we can't afford to freeze the application just because of that. That's reasonable, however I still feel it can make code more complicated than it should.

What I'm going to do is loading the xml file before creating the object, and passing it as a parameter to the constructor. That way I'll make sure the object has the xml file loaded when it's needed. This however is also not an ideal solution, because now I have to make another class responsible for the "private things" of Foo.

Any better ideas?

回答3:

i think, there is an "after" event with load.

so you have to split the call to the new() and the call to the do() in two distinct methods, so the new() is called in initalisation and do() is calld after loading()

pseudosyntax:

beforeInitialisation()
  disableDoSomething()
  new()...
  loader.addEvent(AFTERLOAD, afterLoad)


afterLoad()
  enableDoSomething()


someMethod()
  doSomething()

回答4:

Old question but I bet a lot of people still come here so, here's my solution.

Create a custom event that you dispatch inside of the function that handles the resultEvent

Have the object you want to do something, i think in this case it was foo, to listen for this custom event which then would call doSomething().

回答5:

Call foo.doSomething(); from inside an event handler for the XML loading event (e.g. EVENT.Complete or somesuch depending on how exactly you are loading the file). That is the recommended way to go.

来源：https://stackoverflow.com/questions/638085/flex-3-synchronously-loading-an-xml-file

标签

xml

apache-flex

synchronous