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Hopefully most of this terminology will become clear as we pursue these lessons.
We have reached the point in this discussion where I should provide some examples of ActionScript 3 class definitions so that you can get a preview ofwhat lies ahead.
The code beginning with the word public in Listing 1 is the definition of a very simple class named MyClass . I don't expect this code to mean much to you at this point. Suffice it to say that an object of this class is anew GUI component consisting of a Button object, a RadioButton object, and a NumericStepper object, all contained in a VBox object.
package Classes{
import mx.containers.VBox;import mx.controls.Button;
import mx.controls.RadioButton;import mx.controls.NumericStepper;public class MyClass extends VBox{
//Constructor followspublic function MyClass(){
addChild(new Button());addChild(new RadioButton());
addChild(new NumericStepper());setStyle("backgroundColor",0xFFFF00);
}//end constructor}//end class
}//end package A new data type
The definition of the class creates a new data type, which is unknown to the compiler until it is defined by the programmer.
Two instances (objects) of the class named MyClass
Two objects of the new class named MyClass are shown in Figure 2. You should be able to spot the Button object (rectangular) , the RadioButton object (circular) , and the NumericStepper object in each of the two MyClass objects.
A yellow background
Normally you can't see a VBox object. You can only see the components that it contains. However, I included code in Listing 1 to set the background style of the VBox object to yellow to make it possible for you to visually separate the two new custom objects in Figure 2.
The Flex MXML file
Listing 2 shows the Flex file that was used to instantiate the two objects of the class named MyClass and to display them in the Flash Player window in a browser.
<?xml version="1.0" encoding="utf-8"?><!--SimpleClass01 --><mx:Application
xmlns:mx="http://www.adobe.com/2006/mxml"xmlns:classes="Classes.*"><classes:MyClass /><classes:MyClass /></mx:Application> The two lines of code beginning with the words classes in Listing 2 cause thetwo new objects to be instantiated and displayed.
One of the standard Flex components is named TextArea . This component is an object of the ActionScript class having the same name.
A custom component that extends TextArea
As an example of creating a new custom component that extends an existing class, I will present and discuss a new custom component that extends the TextArea class. The new class is named NumericTextAreaA.
An object of the NumericTextAreaA class behaves just like an object of the standard TextArea class except that the new component will only accept numeric characters, the space character, the backspace character, and the return character. Allother characters are rejected when the user attempts to type them into the text area.
Notification Switch
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