Actionscript 3.0 -> How to override a protected method from UIComponent - apache-flex

Question

I want to create a custom button in ActionScript.
This is my code:
import flash.events.MouseEvent;
import mx.controls.Alert;
import spark.components.Button;
public class BookViewButton extends Button
{
public function BookViewButton()
{
super();
}
override protected function mouseOver(event:MouseEvent,increase:int,newImageSource:String):void{
Alert.show("mouseOver for new class works");
}
}
But Adobe Flash Builder signals the method overriding line as an error.
I tried to change the new method signature so that it would match exactly, like this: (I thought the error might be because I was adding extra parameters to the mouseOver function so Flex might have not recognized it as an overriding)
override protected function mouseOver(event:MouseEvent):void{
Alert.show("mouseOver for new class works");
}
But still it doesn't work. Same little red exclamation mark comes up to signal a mistake.
I'd greatly appreciate any help. Thanks.

Answer 1

What SDK version do you use if you have mouseOver() method in Spark Button hierarchy?
Spark button has mouseEventHandler() method to override:
override protected function mouseEventHandler(event:Event):void
{
super.mouseEventHandler(event);
var mouseEvent:MouseEvent = event as MouseEvent;
if (event.type == MouseEvent.ROLL_OVER)
{
// My roll over logic here
}
}
And it is better to post the error text which IDE gives you. To copy it just open Problems view in Flash Builder, found your error message and copy it via context menu.

Answer 2

You can't use override here because the base class Button does not have a method mouseOver to override.
If you remove the override keyword it should work fine. That said, you'll need to actually add a listener for your function for it to be called when you mouse over. Like this:
import flash.events.MouseEvent;
import mx.controls.Alert;
import spark.components.Button;
public class BookViewButton extends Button
{
public function BookViewButton()
{
addEventListener(MouseEvent.MOUSE_OVER, _mouseOver);
}
private function _mouseOver(event:MouseEvent):void
{
Alert.show("mouseOver for new class works");
}
}
Info on super();
There's no need to call super in the constructor of an extending class, unless there are arguments that you want to parse. Example.
package
{
public class A extends Object
{
public function A()
{
trace("A");
}
}
}
And the extending class:
package
{
public class B extends A
{
public function B()
{
trace("B");
}
}
}
If we do:
var thing:B = new B();
You will have the output:
A
B
However, if you wanted arguments for your constructor, you would need to parse them up to the constructor of the class you're extending using super(). Like so:
public class A extends Object
{
public function A(arg:String)
{
trace(arg);
}
}
public class B extends A
{
public function B(arg:String)
{
super(arg);
}
}
Now this will output "asdf":
var thing:B = new B("asdf");