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A snapshot of the Flex Builder 3 console
Figure 2 shows a snapshot of the console window in the Flex Builder 3 IDE when the above procedure was executed in debug mode.
The three lines of text beginning with the word Activated were produced when the Flash Player gained operating system focus. The three lines oftext beginning with the word Deactivated were produced when the Flash Player lost operating system focus.
The currentTarget and target properties of the Event object
For an explanation of the currentTarget and the target properties shown in Figure 2, see the excellent article titled Understanding the AS3 Event Flow by Jody Hall. As you will see in the next sample program, this information can be used to identify the component thatdispatched the event.
Will discuss in fragments
I will explain the code for ActivateEvent01 in fragments. A complete listing of the class file is provided in Listing 15near the end of the lesson.
Beginning of Driver class for ActivateEvent01
Listing 2 shows the beginning of the Driver class for ActivateEvent01 .
package CustomClasses{
import flash.events.Event;import mx.containers.VBox;
import mx.controls.Label;public class Driver extends VBox{public function Driver(){
setStyle("borderStyle","inset");setStyle("borderColor",0xFF0000);
height=100;var label:Label = new Label();
label.text = "Click browser in debug mode"label.setStyle("color",0xFFFF00);
addChild(label);addEventListener(Event.ACTIVATE,activateHandler);addEventListener(Event.DEACTIVATE,
deActivateHandler);}//end constructor Extends the VBox class
The entire program is written in the Driver class and illustrates the activate and deactivate events of the EventDispatcher class.
This class extends the VBox class, so an object of this class is a VBox object.
Register event listeners
The first statement beginning with addEventListener registers an event listener on the VBox object causing it to execute the method named activateHandler when the Flash Player gains operating system focus and becomes the activeprogram.
The second statement beginning with addEventListener registers an event listener on the VBox causing it to execute the deActivateHandler method when the Flash Player loses operating system focus and is no longer the active program.
The event handler methods
The two event handler methods are shown in Listing 3.
private function activateHandler(event:Event):void{
trace("\nActivated\ncurrentTarget = "+ event.currentTarget
+ "\ntarget = "+ event.target);
}//end activateHandler//-----------------------------=-------------------//private function deActivateHandler(event:Event):void{
trace("\nDeactivated\ncurrentTarget = "+ event.currentTarget
+ "\ntarget = "+ event.target);
}//end deActivateHandler}//end class
}//end package Output produced by the trace function
When the methods are executed in debug mode, the call to the trace function extracts and displays property values from the incoming Event object.
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