Flex软件中经常需要使用一些外部的资源,如图片、声音、SWF或字体,第一种你也可以在软件运行的时候引入和载入,第二种可能经常需要直接将这些资源编译(Compile)到软件中,也就是直接嵌入资源(Embedding Assets)。Flex中可以直接嵌入图片image,影片movie,MP3,和TrueType文字。
直接引用资源
这种方式相对第二种速度慢,但用起来比较灵活。但我个人感觉flex的控件设计的不够方便,
Image能接收Class,也能接收Bitmap,但是Icon不能接收Bitmap,Icon只能接收的是 Class对象。这就给用的人带来了很大的困扰。但由于很多人都遇到了这个问题,所以网上很多人使用IconUtility来实现直接引用资源。
package com.emavaj.myfriend.util { import flash.display.BitmapData; import flash.display.Loader; import flash.display.LoaderInfo; import flash.events.Event; import flash.geom.Matrix; import flash.net.URLRequest; import flash.system.LoaderContext; import flash.utils.Dictionary; import mx.containers.accordionClasses.AccordionHeader; import mx.controls.tabBarClasses.Tab; import mx.core.BitmapAsset; import mx.core.UIComponent; /** * Provides a workaround for using run-time loaded graphics in styles and properties which require a Class reference */ public class IconUtility extends BitmapAsset { private static var dictionary:Dictionary; /** * Used to associate run-time graphics with a target * @param target A reference to the component associated with this icon * @param source A url to a JPG,PNG or GIF file you wish to be loaded and displayed * @param width Defines the width of the graphic when displayed * @param height Defines the height of the graphic when displayed * @return A reference to the IconUtility class which may be treated as a BitmapAsset * @example <mx:Button id="button" icon="{IconUtility.getClass(button,'http://www.yourdomain.com/images/test.jpg')}" /> */ public static function getClass( target:UIComponent,source:String,width:Number = NaN,height:Number = NaN ):Class { if(!dictionary) { dictionary = new Dictionary(false); } //if(source is String) { var loader:Loader = new Loader(); loader.load(new URLRequest(source as String),new LoaderContext(true)); //source = loader; //} dictionary[target] = { source:loader,width:width,height:height }; return IconUtility; } /** * @private */ public function IconUtility():void { addEventListener(Event.ADDED,addedHandler,false,true) } private function addedHandler(event:Event):void { if(parent) { if(parent is AccordionHeader) { var header:AccordionHeader = parent as AccordionHeader; getData(header.data); } else if(parent is Tab) { var tab:Tab = parent as Tab; getData(tab.data); } else { getData(parent); } } } private function getData(object:Object):void { var data:Object = dictionary[object]; if(data) { var source:Object = data.source; if(data.width > 0 && data.height > 0) { bitmapData = new BitmapData(data.width,data.height,true,0x00FFFFFF); } if(source is Loader) { var loader:Loader = source as Loader; if(!loader.content) { loader.contentLoaderInfo.addEventListener(Event.COMPLETE,completeHandler,true); } else { displayLoader(loader); } } } } private function displayLoader( loader:Loader ):void { if(!bitmapData) { bitmapData = new BitmapData(loader.content.width,loader.content.height,0x00FFFFFF); } bitmapData.draw(loader,new Matrix(bitmapData.width/loader.width,bitmapData.height/loader.height,0)); if(parent is UIComponent) { var component:UIComponent = parent as UIComponent; component.invalidateSize(); } } private function completeHandler(event:Event):void { if(event && event.target && event.target is LoaderInfo) { displayLoader(event.target.loader as Loader); } } } }
第二种方式是嵌入资源方式
嵌入资源的利处:
2、可以用简单的变量访问方式,在多个地方引用所嵌入的资源。这是变量就代表资源,提高写代码的效率;
嵌入资源的弊处:
1、增大了SWF文件的大小,因为是将资源直接包含;
2、由于SWF文件增大,将使得初始化的速度变慢;
3、当资源改变后,需要重新编译SWF文件;
例子1:一个简单的嵌入资源的例子:
<?xml version=”1.0”?>
<!-- embed/ButtonIcon.mxml -->
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml”>
<mx:Button label=”Icon Button” icon=”@Embed(source=’logo.gif’)"/>
</mx:Application>
以上粗体部分,使用了@Embed()指令,将logo.gif这个图片直接嵌入到程序中,作为Button按钮的Icon图标。
例子2:用变量引用嵌入的资源
<?xml version="1.0"?>
<!-- embed/ButtonIconClass.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
<mx:Script>
<![CDATA[
[Embed(source="logo.gif")]
[Bindable]
public var imgCls:Class;
]]>
</mx:Script> AdobE FLEX 3 BETA 2
<mx:Button label="Icon Button 1" icon="{imgCls}"/>
<mx:Button label="Icon Button 2" icon="{imgCls}"/>
以上粗体部分,表示将logo.gif图片嵌入,并让变量imgCls可以引用该资源。[Bindable]表示该变量imgCls是可以被数据绑定的。之后,就可以在多个地方引用该嵌入资源的变量(见红色粗体)。
另外也可以通过Embed()指令,在样式表中嵌入资源,这通常是在设置UI组件的皮肤时候使用。如下代码:
<?xml version="1.0"?>
<!-- embed/ButtonIconCSS.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
<mx:Style>
.myCustomButton {
overSkin:Embed(source="overIconImage.gif");
upSkin:Embed(source="upIconImage.gif");
downSkin:Embed(source="downIconImage.gif");
}
</mx:Style>
<mx:Button label="Icon Button Style Def" styleName="myCustomButton"/>
</mx:Application>
以上代码表示在按钮的常态(up)、鼠标悬停(over)、鼠标按下(down)的状态,使用不同的皮肤。overSkin、 upSkin、downSkin是Button的对应状态下的皮肤属性。