Freddie's Ria World

6.4过滤DataGrid数据项

发表时间：18. Dec, 2009 作者：Freddie.

主要功能： 对dataprovider里面的data进行过滤~
代码：
<?xml version=”1.0″ encoding=”utf-8″?>
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml” layout=”absolute” applicationComplete=”oninit()”>
    <mx:Script>
        <![CDATA[
            import mx.collections.ArrayCollection;
            import mx.rpc.events.ResultEvent;
            [Bindable]
            private var items:ArrayCollection;
            private function oninit():void{
                this.srv.send();
            }
            private function onResult(event:ResultEvent):void{
                this.items=event.result.item;
            }
            private function applyFilter():void{
                if (this.items.filterFunction == null)
                {
                    this.items.filterFunction=this.filterNames;
                }
                this.items.refresh();
            }
            private function filterNames(item:Object):Boolean{
                var match:Boolean = true;
                if(nameFilter.text!=””){
                    var name:String = item["name"];
                    var filter:String =nameFilter.text;
                    if(!name||name.toLowerCase().indexOf(filter.toLowerCase())<0){
                        [...]

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3.22在容器中滚动到某个指定的子组件

发表时间：18. Dec, 2009 作者：Freddie.

code:
<mx:Canvas xmlns:mx=”http://www.adobe.com/2006/mxml”
           width=”800″
           height=”600″>
    <mx:Script>
        <![CDATA[
            private function showScrollValue():void
            {
                trace(this.verticalScrollPosition + " " + this.horizontalScrollPosition);
            }
            private function changeScrollToShowChild():void
            {
                vbox.verticalScrollPosition=(returnChildrenHeights((comboBox.selectedItem as Number)-1));
            }
//Vbox 内所有子组件的高度用以计算并确定一个y 值来设定verticalScrollPosition 属性，从而使Vbox 滚动到指定的子组件的位置。
            private function returnChildrenHeights(index:int):Number
            {
                var i:int=0;
                var sumHeight:Number=0;
                while (i < index)
                {
                    sumHeight+=vbox.getChildAt(i).height;
                    i++;
                }
                return sumHeight;
            }
        ]]>
    </mx:Script>
    <mx:ComboBox id=”comboBox”
                 change=”changeScrollToShowChild()”>
        <mx:dataProvider>
            <mx:Array>
                [...]

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3.15使用延迟实例化提高启动效率

发表时间：18. Dec, 2009 作者：Freddie.

问题
我们要保证组件仅仅在需要显示在屏幕上的时候才被创建。
Container 类默认情况下仅仅在要显示组件的时候创建它，因为UIComponent 默认的
creationPolicy 值为auto。换句话说，当视图(view)设置成可视的时候，如果还没有创建
该视图，则组件会实例化此视图
code:
<mx:Canvas xmlns:mx=”http://www.adobe.com/2006/mxml”
           height=”600″
           width=”600″>
    <mx:Script>
        <![CDATA[
            private function changeViewStackCreation():void
            {
                viewStack.creationPolicy=(comboBox.selectedItem as String);
                viewStack.createComponentsFromDescriptors(true);
            }
            private function changeViewStack():void
            {
                viewStack.selectedIndex=comboBoxChangeIndex.selectedIndex;
            }
        ]]>
    </mx:Script>
    <mx:Fade alphaFrom=”0″
             alphaTo=”1″
             duration=”4000″
             id=”fadeIn”/>
    <mx:ComboBox dataProvider=”{['none', 'all', 'queued',
'auto']}”
                 change=”changeViewStackCreation()”
                 id=”comboBox”/>
    <mx:ComboBox dataProvider=”{[1, 2, 3, 4]}”
                 x=”150″
                 change=”changeViewStack()”
                 id=”comboBoxChangeIndex”/>
    <mx:ViewStack id=”viewStack”
                  width=”400″
                  height=”300″
                  creationPolicy=”none”
                  y=”100″>
        <mx:Canvas creationCompleteEffect=”{fadeIn}”
                   creationIndex=”0″
                   backgroundColor=”#0000ff”
                   [...]

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3.13 通过LinkBar 控制ViewStack

发表时间：18. Dec, 2009 作者：Freddie.

使用LinkBar 的selectedIndex 或selectedItem 属性的任意之一可以决定显示ViewStack
的哪一条。
code:
<?xml version=”1.0″ encoding=”utf-8″?>
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml” layout=”absolute”>
    <mx:Script>
        <![CDATA[
            [Bindable]
            private var indext:int =0;
            private function changeIndex():void{
                if(indext==2){
                    indext=0;
                }else{
                    indext++;
                }
            }
        ]]>
    </mx:Script>
    <mx:Canvas click=”changeIndex()”>   
        <mx:ViewStack selectedIndex=”{indext}”>
            <mx:VBox>
            <mx:Image  source=”BFC069.gif”/>   
            </mx:VBox>
            <mx:VBox>
                <mx:Image  source=”BFC204.gif”/>
            </mx:VBox>
            <mx:VBox>
                <mx:Image  source=”FC229I.gif”/>
            </mx:VBox>
        </mx:ViewStack>
    </mx:Canvas>
</mx:Application>
注：viewstack里必须为容器，我们这里用了vbox~
这里可以实现相册浏览的效果（当然是最简易的拉~~）

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2.6设置控件的labelFunction

发表时间：18. Dec, 2009 作者：Freddie.

很多时候我们需要combobox里面的标签是一个组合，而不单单只是一个LABEL，怎么解决呢，看代码：
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml”
layout=”horizontal”>
<mx:ComboBox dataProvider=”{myDP}”
labelFunction=”getFullName”/>
<mx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
[Bindable]
private var myDP:ArrayCollection=new ArrayCollection([{id: 1, fName: "Lucky", lName: "Luke"}, {id: 2, fName: "Bart", lName: "Simpson"}]);

private function getFullName(item:Object):String
{
return item.fName + ” ” + item.lName;
}
]]>
</mx:Script>
</mx:Application>
combobox为我们提供了 labelFunction这个功能 ，你可以自定义自己所需要的信息作为标签~

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1.15监听键盘事件

发表时间：18. Dec, 2009 作者：Freddie.

解决思路:
为应用程序的stage或组件的keyDown事件添加监听器，读取KeyboardEvents的keyCode属性。
<?xml version=”1.0″ encoding=”utf-8″?>
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml”
                layout=”absolute”
                KeyDown=”KeyHandler(event)”
                xmlns:ns1=”*”>
    <mx:Script>
        <![CDATA[
            import flash.events.KeyboardEvent;
            private function keyHandler(event:KeyboardEvent):void
            {
                switch (event.keyCode)
                {
                    case 13:
                        trace("Enter pressed");
                        break;
                    case 32:
                        trace("SpaceBar");
                        break;
                    case 16:
                        trace("ShiftKeypressed");
                        break;
                    case 112:
                        trace("F1pressed");
                        break;
                    case 8:
                        trace("Deletepressed");
                        break;
                }
            }
        ]]>
    </mx:Script>
    <mx:Button   />
</mx:Application>
运行，没反应？？？ 注意下面放了一个BUTTON，cookbook解释说它必须被激活才能监听到它发出来的事件，
也就是说必须得先按一下，麻烦吧~ 不过，还有简单点的办法。
把上面的KeyDown监听换成下面这一句
addedToStage=”stage.addEventListener(KeyboardEvent.KEY_DOWN, keyHandler)”
也就是给舞台一个一事件监听，这下就不用激活BUTTON拉··

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