Apache flex 找出Flex中已放置到的树项

我有一个mx.List和一个mx.Tree。我试图将项目从列表拖到树上，但不是让它们添加到实际的树上，我只是想知道树上的dropTarget是什么。dropTarget变量始终为

null

protected function sparkTree_dragDropHandler(event:DragEvent):void
{
    var source:* = event.dragInitiator;
    var target:* = event.currentTarget;

    trace("Dragged......", source.selectedItem.label);
    trace("From.........", source.name);
    trace("To...........", event.currentTarget.name);
    trace("Target Item..", event.currentTarget.dropTarget);
}

输出：

Dragged...... itemOne
From......... _Main_Tree2
To........... _Main_Tree1
Target Item.. null

所以我只是想澄清一下，我正试图得到物品被扔到的物体

---

作为旁注，使用：

var source:List = event.dragInitiator as List;
var target:List = event.currentTarget as List;

导致空对象引用错误。看起来很奇怪

---

更新： （不确定在哪里张贴这篇文章是最好的，但）我认为这可能是解决方案

创建自定义事件：ItemDrageEvent

package events
{
    import mx.core.DragSource;
    import mx.core.IUIComponent;
    import mx.events.DragEvent;

    public class ItemDragEvent extends DragEvent
    {
        public static const DRAG_DROP:String = "itemDragDrop";
        public static const DRAG_ENTER:String = "itemDragEnter";
        public static const DRAG_EXIT:String = "itemDragExit";

        public var item:Object;
        public var data:Object;
        public var index:Object;

        public function ItemDragEvent(type:String, bubbles:Boolean=false, cancelable:Boolean=true, dragInitiator:IUIComponent=null, dragSource:DragSource=null, action:String=null, ctrlKey:Boolean=false, altKey:Boolean=false, shiftKey:Boolean=false)
        {
            super(type, bubbles, cancelable, dragInitiator, dragSource, action, ctrlKey, altKey, shiftKey);
        }
    }
}

创建mx.Tree项渲染器：TreeItemRenderer

<?xml version="1.0" encoding="utf-8"?>
<s:MXTreeItemRenderer xmlns:fx="http://ns.adobe.com/mxml/2009" 
                  xmlns:s="library://ns.adobe.com/flex/spark" 
                  xmlns:mx="library://ns.adobe.com/flex/mx"
                  dragEnter="dragEnterHandler(event)"
                  dragExit="dragExitHandler(event)"
                  dragDrop="dragDropHandler(event)"
                  >

<fx:Script>
    <![CDATA[
        import events.ItemDragEvent;

        import mx.core.IUIComponent;
        import mx.events.DragEvent;
        import mx.managers.DragManager;


        protected function dragEnterHandler(event:DragEvent):void
        {
            DragManager.acceptDragDrop(event.currentTarget as IUIComponent);

            var e:ItemDragEvent = new ItemDragEvent(ItemDragEvent.DRAG_ENTER, true);
            e.data = data;
            e.item = data;
            e.index = itemIndex;
            dispatchEvent(e);   

            trace("TreeItemRenderer, dragEnterHandler");
        }

        protected function dragExitHandler(event:DragEvent):void
        {
            var e:ItemDragEvent = new ItemDragEvent(ItemDragEvent.DRAG_EXIT, true);
            e.data = data;
            e.item = data;
            e.index = itemIndex;
            dispatchEvent(e);

            trace("TreeItemRenderer, dragExitHandler");
        }

        protected function dragDropHandler(event:DragEvent):void
        {
            DragManager.acceptDragDrop(event.currentTarget as IUIComponent);

            var e:ItemDragEvent = new ItemDragEvent(ItemDragEvent.DRAG_DROP, true);
            e.data = data;
            e.item = data;
            e.index = itemIndex;
            dispatchEvent(e);

            trace("TreeItemRenderer, dragDropHandler");
        }

    ]]>
</fx:Script>

<s:states>
    <s:State name="normal" />            
    <s:State name="hovered" />
    <s:State name="selected" />
</s:states>
<s:HGroup left="0" right="0" top="0" bottom="0" verticalAlign="middle">
    <s:Rect id="indentationSpacer" width="{treeListData.indent}" percentHeight="100" alpha="0">
        <s:fill>
            <s:SolidColor color="0xFFFFFF" />
        </s:fill>
    </s:Rect>
    <s:Group id="disclosureGroup">
        <s:BitmapImage source="{treeListData.disclosureIcon}" visible="{treeListData.hasChildren}" />
    </s:Group>
    <s:BitmapImage source="{treeListData.icon}" />
    <s:Label id="labelField" text="{treeListData.label}" paddingTop="2"/>
</s:HGroup>
</s:MXTreeItemRenderer>

最后是主代码

需要做一些工作来整理视觉反馈，但这应该会输出掉到的树项目。

关于

var source:List = event.dragInitiator as List;
var target:List = event.currentTarget as List;

尝试检查您的导入。可能有导入的Spark列表，但您使用的是MX列表？：）

关于

dropTarget

属性，请参阅。它与Flex拖放功能无关。所以这个属性的值为null也就不足为奇了

一般来说，您可以使用以下代码段，它不能解决所有问题（我没有时间调试所有方面），但可以为您提供一些良好的起点：

<?xml version="1.0" encoding="utf-8"?>
<s:Application minHeight="600" minWidth="955" xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:mx="library://ns.adobe.com/flex/mx" xmlns:s="library://ns.adobe.com/flex/spark">
    <fx:Script>
    <![CDATA[
        import mx.collections.ArrayCollection;
        import mx.collections.ICollectionView;
        import mx.events.DragEvent;
        import mx.managers.DragManager;

        [Bindable]
        private var listDataProvider:ArrayCollection = new ArrayCollection([ "First", "Second", "Third" ]);
        [Bindable]
        private var treeDataProvider:Object =
            { label: "First", children: new ArrayCollection([ { label: "Second" }, { label: "Third" } ]) };

        protected function list_dragCompleteHandler(event:DragEvent):void
        {
            if (event.relatedObject == tree)
            {
                event.preventDefault();
                if (event.action == DragManager.MOVE && list.dragMoveEnabled)
                {
                    var items:Array = event.dragSource.dataForFormat("items") as Array;
                    var collection:ArrayCollection = list.dataProvider as ArrayCollection;
                    for each (var item:Object in items)
                    {
                        if (collection.contains(item))
                            collection.removeItemAt(collection.getItemIndex(item));
                    }
                }
            }
        }

        protected function tree_dragDropHandler(event:DragEvent):void
        {
            var source:List = List(event.dragInitiator);
            var target:Tree = Tree(event.currentTarget);

            trace("Dragged......", source.selectedItem);
            trace("From.........", source.name);
            trace("To...........", target.name);
            event.preventDefault();
            tree.hideDropFeedback(event);
            var index:int = tree.calculateDropIndex(event);
            var items:Array = new Array();
            if (event.dragSource.hasFormat("treeItems"))
                items = items.concat(event.dragSource.dataForFormat("treeItems") as Array);
            if (event.dragSource.hasFormat("items"))
                items = items.concat(event.dragSource.dataForFormat("items") as Array);
            if (index > (tree.dataProvider as ICollectionView).length)
                index = (tree.dataProvider as ICollectionView).length;
            for each (var item:Object in items)
            {
                var obj:Object = new Object()
                obj.label = item;

                (tree.dataProvider as ArrayCollection).addItemAt(obj, index);

            }
        }

        protected function tree_dragEnterHandler(event:DragEvent):void
        {
            if (event.dragInitiator == list)
            {
                event.preventDefault();
                DragManager.acceptDragDrop(event.target as Tree);
                tree.showDropFeedback(event);
            }
        }

        protected function tree_dragExitHandler(event:DragEvent):void
        {
            event.preventDefault();
            tree.hideDropFeedback(event);
        }

        protected function tree_dragOverHandler(event:DragEvent):void
        {
            if (event.dragInitiator == list)
            {
                event.preventDefault();
                tree.showDropFeedback(event);
            }
        }
    ]]>
    </fx:Script>
    <s:layout>
        <s:HorizontalLayout horizontalAlign="center" verticalAlign="middle" />
    </s:layout>
    <mx:List dataProvider="{listDataProvider}" dragComplete="list_dragCompleteHandler(event)" dragEnabled="true"
        dragMoveEnabled="true" dropEnabled="true" id="list" width="200" />
    <mx:Tree dataProvider="{treeDataProvider}" dragDrop="tree_dragDropHandler(event)" dragEnabled="true"
        dragEnter="tree_dragEnterHandler(event)" dragExit="tree_dragExitHandler(event)"
        dragOver="tree_dragOverHandler(event)" dropEnabled="true" id="tree" showRoot="true" width="200" />
</s:Application>

（tree.dataProvider作为ICollectionView）.length）
索引=（tree.dataProvider作为ICollectionView）.length；
对于每个（变量项：项中的对象）
{
var obj:Object=新对象（）
obj.label=项目；
（tree.dataProvider作为ArrayCollection）.addItemAt（obj，索引）；
}
}
受保护的功能树\u dragEnterHandler（事件：DragEvent）：无效
{
if（event.draginInitiator==列表）
{
event.preventDefault（）；
DragManager.acceptDragDrop（作为树的event.target）；
树。showDropFeedback（事件）；
}
}
受保护的函数树\u dragExitHandler（事件：DrageEvent）：void
{
event.preventDefault（）；
hideDropFeedback（事件）；
}
受保护的功能树\u dragOverHandler（事件：DragEvent）：无效
{
if（event.draginInitiator==列表）
{
event.preventDefault（）；
树。showDropFeedback（事件）；
}
}
]]>

@Constantiner是的<代码>变量源：mx.controls.List=event.draginInitiator作为mx.controls.List；变量目标：mx.controls.List=event.currentTarget作为mx.controls.List旁注的答案是正确的，而不是关键问题。@Constantiner我文章的主要焦点是发现树/列表组件中的哪个元素被放到了-我还没有答案。作为我在将

event.draginInitiator

和

event.currentTarget

转换为列表时提到的一个旁注，我得到了一个错误（第一个代码块将它们设置为非类型化）。你对旁注的回答是正确的，但是这篇文章的重点是找出Flex中哪个树项目被删除了，这一点仍然没有得到回答。

<?xml version="1.0" encoding="utf-8"?>
<s:Application minHeight="600" minWidth="955" xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:mx="library://ns.adobe.com/flex/mx" xmlns:s="library://ns.adobe.com/flex/spark">
    <fx:Script>
    <![CDATA[
        import mx.collections.ArrayCollection;
        import mx.collections.ICollectionView;
        import mx.events.DragEvent;
        import mx.managers.DragManager;

        [Bindable]
        private var listDataProvider:ArrayCollection = new ArrayCollection([ "First", "Second", "Third" ]);
        [Bindable]
        private var treeDataProvider:Object =
            { label: "First", children: new ArrayCollection([ { label: "Second" }, { label: "Third" } ]) };

        protected function list_dragCompleteHandler(event:DragEvent):void
        {
            if (event.relatedObject == tree)
            {
                event.preventDefault();
                if (event.action == DragManager.MOVE && list.dragMoveEnabled)
                {
                    var items:Array = event.dragSource.dataForFormat("items") as Array;
                    var collection:ArrayCollection = list.dataProvider as ArrayCollection;
                    for each (var item:Object in items)
                    {
                        if (collection.contains(item))
                            collection.removeItemAt(collection.getItemIndex(item));
                    }
                }
            }
        }

        protected function tree_dragDropHandler(event:DragEvent):void
        {
            var source:List = List(event.dragInitiator);
            var target:Tree = Tree(event.currentTarget);

            trace("Dragged......", source.selectedItem);
            trace("From.........", source.name);
            trace("To...........", target.name);
            event.preventDefault();
            tree.hideDropFeedback(event);
            var index:int = tree.calculateDropIndex(event);
            var items:Array = new Array();
            if (event.dragSource.hasFormat("treeItems"))
                items = items.concat(event.dragSource.dataForFormat("treeItems") as Array);
            if (event.dragSource.hasFormat("items"))
                items = items.concat(event.dragSource.dataForFormat("items") as Array);
            if (index > (tree.dataProvider as ICollectionView).length)
                index = (tree.dataProvider as ICollectionView).length;
            for each (var item:Object in items)
            {
                var obj:Object = new Object()
                obj.label = item;

                (tree.dataProvider as ArrayCollection).addItemAt(obj, index);

            }
        }

        protected function tree_dragEnterHandler(event:DragEvent):void
        {
            if (event.dragInitiator == list)
            {
                event.preventDefault();
                DragManager.acceptDragDrop(event.target as Tree);
                tree.showDropFeedback(event);
            }
        }

        protected function tree_dragExitHandler(event:DragEvent):void
        {
            event.preventDefault();
            tree.hideDropFeedback(event);
        }

        protected function tree_dragOverHandler(event:DragEvent):void
        {
            if (event.dragInitiator == list)
            {
                event.preventDefault();
                tree.showDropFeedback(event);
            }
        }
    ]]>
    </fx:Script>
    <s:layout>
        <s:HorizontalLayout horizontalAlign="center" verticalAlign="middle" />
    </s:layout>
    <mx:List dataProvider="{listDataProvider}" dragComplete="list_dragCompleteHandler(event)" dragEnabled="true"
        dragMoveEnabled="true" dropEnabled="true" id="list" width="200" />
    <mx:Tree dataProvider="{treeDataProvider}" dragDrop="tree_dragDropHandler(event)" dragEnabled="true"
        dragEnter="tree_dragEnterHandler(event)" dragExit="tree_dragExitHandler(event)"
        dragOver="tree_dragOverHandler(event)" dropEnabled="true" id="tree" showRoot="true" width="200" />
</s:Application>