AS3 Textbox Change Event Not Firing

问题:

I built a quiz game with a cartoon question bubble. The bubble is re sized to the length of the question. I want to a change event on the dynamic textbox to call a function that changes the size of the question bubble.

However, the change event is never called when my textbox value is modified dynamically from code.

 question_txt.addEventListener(Event.CHANGE, setTextBubbleSize);

 function setTextBubbleSize(event:Event):void
    {
        trace("QUESTION TEXT CHANGED");
        textBubble_mc.height = 30 + question_txt.text.length * 1.2;
        if (textBubble_mc.height > 170) textBubble_mc.height = 170;
        question_txt.y = textBubble_mc.y - textBubble_mc.height / 6 + 10;
    }

I want to use the change event because there are several places in my code that question_txt can be set. How can I get the textbox to fire the change event?

Also, is there a way to count the number of lines in question_txt to more accurately set the height of textBubble_mc?

回答1:

Yes, as David comments, TextField only dispatches CHANGE events when it's being edited by user input - in fact, this is generally true of most components. The reason, of course, is because if you manually tried to change the field's value inside your "change" handler, you'd make a recursive cycle of events that you'd have to manually detect your way out of.

What you want to do is make a wrapper function, like:

function setQuestionText( s:String ):void
    {
        question_txt.text = s;
        setTextBubbleSize();
    }

For your other question, there is no reason to estimate the textfield's height based on the number of lines or characters - just set the text property, and you can immediately query the textfield's height. It will accurately reflect the field's new height, and if you change the field's width, the height will immediately be updated, etc.

Or, if you need to know any fine details about the size of the text field, you can always use TextExtent.

回答2:

I don't think the CHANGE event is fired when you change the textbox's properly with as3. But you can always raise the event by:

dispatchEvent(new Event(Event.CHANGE, true));

For the number of lines in the textbox, you can use the numLines properly of the TextField

http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/text/TextField.html#numLines

回答3:

As I see the solutions, this is another class that extends the TextField. Sample code:

package {
import flash.events.Event;
import flash.text.TextField;

public class MyTf extends TextField {
    public function MyTf() {
        super();
    }

    override public function set text(value:String):void
    {
        super.text = value;
        dispatchEvent(new Event(Event.CHANGE));
    }

}
}