benwatts.ca » actionscript

Creating Instances from the Library with Strings

Ben — Sun, 20 Dec 2009 18:52:25 +0000

Problem: while working on an AS3 document you uncover an unusual situation in which you have a string class name that corresponds to something in the library. How does one do it?

I’ve come across this a number of times and found myself dropboxing this snippet so I would always have it with me …

import flash.utils.*;

/** 

 * Takes a string classname, returns an instance of that class, if it exists. 

 */

private function newInstanceFromString(className:String):*{

    try{ 

        var classRef:Class = getDefinitionByName(className) as Class; 

        return new classRef();

    } catch( e:ReferenceError ){

        trace('Error: there was a problem creating an instance of the "'+className+'" class. Check your library and linkage to ensure it\'s there.');

        trace(e+"\n"); 

    }

}

See the AS3 livedocs for more information about getDefinitionByName, the super helpful method that makes it all work.

Tinting a Display Object

Ben — Tue, 17 Jun 2008 17:29:35 +0000

Tinting a display object in AS3 is remarkably easy:

// EXAMPLE 1: tint a display object

import fl.motion.Color;

// [..]

var tint:Color = new Color();

tint.setTint( 0x0099ff, 1 );

myobject.transform.colorTransform = tint;

You’ve got two options for resetting the colour, store the original colour or create a new Color object. The following example resets the colour of a display object when it is hovered over.

// EXAMPLE 2: reset with a new Color Object

import fl.motion.Color;

import flash.events.MouseEvent; 

// [..]

// call the hover() function when we hover over the display object:

myobject.addEventListener(MouseEvent.ROLL_OVER, hover); 

private function hover(e:MouseEvent):void{

    e.currentTarget.transform.colorTransform = new Color(); // removes tint

}

Alternatively, you can store the original “colour” of the untinted in a variable before you tint it. The following trivial example demonstrates this, but you wouldn’t see any visible change on the stage (FYI).

// EXAMPLE 3: reset the tint by storing the original value

import fl.motion.Color;

// [..]

var tint:Color = new Color();

tint.setTint( 0x0099ff, 1 );

var originalColour:Color = myobject.transform.colorTransform; // store the original colour.

myobject.transform.colorTransform = tint; // tint the object blue

myobject.transform.colourTransform = originalColour; // tint the object back to its original colour

AS3 Mouse Cursor

Ben — Mon, 26 May 2008 16:22:24 +0000

Movieclips with mouse handlers that make them behave as buttons no longer automatically use the lovable hand cursor. Hence the need for these two properties to be set to true on your DisplayList object!

buttonMode = true;
useHandCursor = true;

Removing Everything from a Display Container

Ben — Mon, 26 May 2008 00:28:24 +0000

I ran into this problem and couldn’t figure out what was going on because I fail miserably:

// doesn't work because as this code executes numChildren is decreasing;

// it ends up not removing everything

for(var i:Number=0; i &lt; numChildren; i++){

  removeChildAt(i);

}

The solution:

while( numChildren > 0 ){

  removeChildAt(0);

}

This expression is useful for deleting things from the bottom of the displayList up.

Add Filters to Display Objects

Ben — Mon, 19 May 2008 15:03:59 +0000

Flash’s built-in filters (eg. blur/drop shadow) can be applied to display objects and bitmaps, though frankly it feels much more straightforward when you’re applying them to a display object instead of a bitmap. But I haven’t done anything with bitmaps yet … so …

All the filters are part of the flash.filters.* class.

// must import above the class definition

import flash.filters.DropShadowFilter;

// -- [..]

var myClip:MovieClip = new MovieClip();

var shadowFilter:DropShadowFilter = new DropShadowFilter(); // takes a lot of arguments ...

myClip.filters = [shadowFilter]; // filters is an instance variable from the DisplayObject class -- 'tis an Array

// if this was a bitmap (as opposed to a DisplayObject) we'd need to do applyFilter() or something

Sifting Through the Display List to Delete Things

Ben — Mon, 19 May 2008 14:31:51 +0000

Hah, it’s a pretty specific case … but this checks the last item of the display list and removes it if it partially matches (indexOf) the name on the display list item. This requires that the display list item to be given a name.

var myClip:MovieClip = new MovieClip();

myClip.name = "thenameofit";

if( getChildAt(numChildren-1).name.indexOf("thenameofit") > -1 ){

    removeChildAt(numChildren-1)

}

Yeah. Heh. So I’m keeping this code around, why? It could be used in the program I’m writing now, but it’s not nearly flexible enough as this, which loops through the display list and removes any child with containing a partially match of “deleteme”. Much more flexible, but also more intensive in a complex movie?

for( var i:int=0; i < this.numChildren; i++ ){

    if( getChildAt(i).name.indexOf('deleteme') > -1 ){

        removeChildAt(i);

    }

}