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An object of the class named NumericTextAreaA
Figure 3 shows the visual manifestation of an object of this class with two lines of numeric and space characters having been entered. (The entry of additional lines of text causes scroll bars to automatically appear.)
A class definition is probably required
It is possible to create simple custom components by embedding ActionScript code in a Flex MXML file. However, I don't believe that it is possible tocreate an object with this behavior without defining a new ActionScript class. Even if it is possible, defining a new class is the approach that makes the mostsense to me.
The file named NumericTextArea01.mxml
The MXML code beginning with cc in Listing 3 instantiates the object shown in Figure 3.
<?xml version="1.0" encoding="utf-8"?><mx:Application
xmlns:mx="http://www.adobe.com/2006/mxml"xmlns:cc="CustomClasses.*"><cc:NumericTextAreaA/></mx:Application> The class definition for NumericTextAreaA
Listing 4 shows the class definition from which the object shown in Figure 3 was instantiated.
/*This is a custom component. This class extends the
TextArea class. It recognizes only the followingcharacters:
0, 1, 2, 3, 4, 5, 6, 7, 8,9space
backspacereturn key
The next numeric character is appended onto the end ofthe string in the text area regardless of the current
position of the cursor.The backspace key deletes characters from the end of the
string, one character at a time.*********************************************************/
package CustomClasses{import mx.controls.TextArea;
import mx.controls.Alert;import flash.events.*
public class NumericTextAreaA extends TextArea{private var theText:String = "";public function NumericTextAreaA(){
this.addEventListener("keyUp",processKey);}//end constructor
private function processKey(event:KeyboardEvent):void{
if(event.charCode==48){theText+="0";
}else if(event.charCode==49){theText+="1";
}else if(event.charCode==50){theText+="2";
}else if(event.charCode==51){theText+="3";
}else if(event.charCode==52){theText+="4";
}else if(event.charCode==53){theText+="5";
}else if(event.charCode==54){theText+="6";
}else if(event.charCode==55){theText+="7";
}else if(event.charCode==56){theText+="8";
}else if(event.charCode==57){theText+="9";
}else if(event.charCode==8){//backspacetheText=
theText.substr(0,theText.length-1);}else if(event.charCode==32){//space
theText+=" ";}else if(event.charCode==13){//return key
theText+="\n";}//end else
this.text=theText;}//end processKey method
}//end class}//end package May not be familiar code
There may be quite a lot of code in Listing 4 with which you are not familiar. However, it is not my purpose in writing this lesson to get into thedetails of defining classes in ActionScript, so I won't take the time to explain this code in this lesson. Suffice it to say that Listing 4checks the character code associated with each keystroke in the text area and rejects all but the numeric characters, the backspace character, the spacecharacter, and the return key.
I will explain code like this in detail in future lessons. For now, simply accept this as an example of why you may need to learn OOP in order toadvance your career as an ActionScript programmer.
Running the ActionScript program named NumericTextArea01
If you have the Flash Player plug-in (version 9 or later) installed in your browser you should be able to run this program by clicking on NumericTextArea01 .
Enter some alphabetic and numeric text in the white box to see how the GUI component behaves. Click the "Back" button in your browser to returnto this page when you are finished experimenting with the component.
If you don't have the proper Flash Player installed, you should be notified of that fact and given an opportunity to download and install the Flash Playerplug-in program.
I will publish a list containing links to ActionScript resources as a separate document. Search for ActionScript Resources in the Connexions searchbox.
-end-
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