TechNote (Archived)

Error when Defining a "Load" Event handler in a Loader Object subclass

Issue

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Defining "load" Event Handler inside any Loader Object subclass generates "Error opening URL" error message.

Reason

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The addEventListener() method requires two parameters: the name of an event, and a reference to a listener. The listener can be either be an object or a function. If you pass an object, the callback function assigned to the object is invoked in the scope of the object. However, if you pass a function, the function is invoked in the scope of a component instance that callsaddEventListener().

In our case the "load" Event Handler calls theLoader.load() method in addition to thehandleEvent() method. This causes the load function to interpret the eventObj parameter as a string inLoader.load(), so it tries to load the URL, generating the error "Error opening URL."

Ref.(98374).

Solution

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There are two approaches to solve this issue:

• Add the following line to the ActionScript code:

   _global.mx.events.EventDispatcher.exceptions.load = 1 ; 

• Delegating the scope of the function by adding the following code:

   import mx.utils.Delegate; this.addEventListener("load", mx.utils.Delegate.create(this, handleEvent)); 

Additional Information

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See also the Developer Center article Proxying Events with the mx.utils.Delegate Class.

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