Flex3组件拖放教程(5)

例子1：从list控件拷贝数据到另外一个list控件< xmlnamespace prefix ="o" ns ="urn:schemas-microsoft-com:office:office" />

这个例子中即使你设置了dropEnabled属性为ture,你仍然按可以自行定义自己的dragDrop事件。当然你需要在自己的事件处理中调用Event.preventDefault()阻止默认的处理事件的执行。之所以设置dropEnabled为true,是因为这样的话程序就可以自动处理除了dragDrop以外的事件了。注意：你可以调用Event.preventDefault()是因为drop target是list-based控件。 任何一个list-based控件都定义了一个默认的dragDrop处理。比如程序中，你可以显示的处理dagDrop事件，也可以使用默认的处理其他事件。对于一个nonlist-base的控件来说，你就不需要调用Event.preventDefault()了，因为只有list-based的控件才定义了默认的拖放事件处理。

<!-- dragdrop\DandDListToListCopy.mxml -->

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

creationComplete="initApp();">

<mx:Script>

<![CDATA[

import mx.events.DragEvent;

import mx.managers.DragManager;

import mx.core.DragSource;

import mx.collections.IList;

import mx.collections.ArrayCollection;

private function initApp():void {

firstList.dataProvider = new ArrayCollection([

{label:"First", data:"1"},

{label:"Second", data:"2"},

{label:"Third", data:"3"},

{label:"Fourth", data:"4"},

]);

secondList.dataProvider = new ArrayCollection([]);

}

private function dragDropHandler(event:DragEvent):void {

if (event.dragSource.hasFormat("items"))

{

// Explicitly handle the dragDrop event.

event.preventDefault();

// Since you are explicitly handling the dragDrop event,

// call hideDropFeedback(event) to have the drop target

// hide the drop indicator.

// The drop indicator is created

// automatically for the list controls by the built-in

// event handler for the dragOver event.

event.currentTarget.hideDropFeedback(event);

// Get drop target.

var dropTarget:List=List(event.currentTarget);

// Get the dragged item from the drag initiator.

// The List control always writes an Array

// to the dragSource object,

// even if there is only one item being dragged.

var itemsArray:Array =

event.dragSource.dataForFormat("items") as Array;

// Copy the dragged data into a new Object.

var tempItem:Object =

{label: itemsArray[0].label, data: itemsArray[0].data};

// Get the drop location in the destination.

var dropLoc:int = dropTarget.calculateDropIndex(event);

// Add the new object to the drop target.

IList(dropTarget.dataProvider).addItemAt(tempItem, dropLoc);

}

}

]]>

</mx:Script>

<mx:HBox>

<mx:List id="firstList"

dragEnabled="true"/>

<mx:List id="secondList"

dropEnabled="true"

dragDrop="dragDropHandler(event);"/>

</mx:HBox>

<mx:Button id="b1"

label="Reset"

click="initApp()"

/>

</mx:Application>

例子2：拷贝数据从list控件到DataGrid控件

你可以拷贝数据到另外一个类型不同的控件，由于他们使用不同的数据格式，要解决这个困境，你必须书写dragDrop事件处理在转换数据格式，使得他们能够兼容。

例子当中，你可以移动或者拷贝数据从list控件到DataGrid控件。事件处理dragDrop中增加了一个新的field到dragged data中用来保存日期。

<?xml version="1.0"?>

<!-- dragdrop\DandDListToDG.mxml -->

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

creationComplete="initApp();">

<mx:Script>

<![CDATA[

import mx.events.DragEvent;

import mx.managers.DragManager;

import mx.core.DragSource;

import mx.collections.IList;

import mx.collections.ArrayCollection;

private function initApp():void {

srcList.dataProvider = new ArrayCollection([

{label:"First", data:"1"},

{label:"Second", data:"2"},

{label:"Third", data:"3"},

{label:"Fourth", data:"4"},

]);

destDG.dataProvider = new ArrayCollection([]);

}

private function dragDropHandler(event:DragEvent):void {

if (event.dragSource.hasFormat("items"))

{

// Explicitly handle the dragDrop event.

event.preventDefault();

// Since you are explicitly handling the dragDrop event,

// call hideDropFeedback(event) to have the drop target

// hide the drop indicator.

// The drop indicator is created

// automatically for the list controls by the built-in

// event handler for the dragOver event.

event.currentTarget.hideDropFeedback(event);

// Get drop target.

var dropTarget:DataGrid =

DataGrid(event.currentTarget);

var itemsArray:Array =

event.dragSource.dataForFormat('items') as Array;

var tempItem:Object =

{ label: itemsArray[0].label,

data: itemsArray[0].data,

date: new Date()

};

// Get the drop location in the destination.

var dropLoc:int = dropTarget.calculateDropIndex(event);

IList(dropTarget.dataProvider).addItemAt(tempItem, dropLoc);

}

}

]]>

</mx:Script>

<mx:HBox>

<mx:List id="srcList"

dragEnabled="true"

dragMoveEnabled="true"/>

<mx:DataGrid id="destDG"

dropEnabled="true"

dragDrop="dragDropHandler(event);">

<mx:columns>

<mx:DataGridColumn dataField="label"/>

<mx:DataGridColumn dataField="data"/>

<mx:DataGridColumn dataField="date"/>

</mx:columns>

</mx:DataGrid>

</mx:HBox>

<mx:Button id="b1"

label="Reset"

click="initApp()"

/>

</mx:Application>