Flex - Tree Control
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Introduction
The Tree control displays hierarchical data arranged as an expandable tree.
Class declaration
Following is the declaration for mx.controls.Tree class:
public class Tree
extends List
implements IIMESupport
Public properties
| S.N. | Property & Description |
|---|---|
| 1 | dataDescriptor : mx.controls.treeClasses:ITreeDataDescriptor Returns the current ITreeDataDescriptor. |
| 2 | dataProvider : Object [override] An object that contains the data to be displayed. |
| 3 | dragMoveEnabled : Boolean [override] Indicates that items can be moved instead of just copied from the Tree control as part of a drag-and-drop operation. |
| 4 | firstVisibleItem : Object The item that is currently displayed in the top row of the tree. |
| 5 | hasRoot : Boolean [read-only] Indicates that the current dataProvider has a root item; for example, a single top node in a hierarchical structure. |
| 6 | itemIcons : Object An object that specifies the icons for the items. |
| 7 | maxHorizontalScrollPosition : Number [override] The maximum value for the maxHorizontalScrollPosition property for the Tree control. |
| 8 | openItems : Object The items that have been opened or set opened. |
| 9 | showRoot : Boolean Sets the visibility of the root item. |
Public methods
| S.N. | Method & Description |
|---|---|
| 1 | Tree() Constructor. |
| 2 | expandChildrenOf(item:Object, open:Boolean):void Opens or closes all the tree items below the specified item. |
| 3 | expandItem(item:Object, open:Boolean, animate:Boolean = false, dispatchEvent:Boolean = false, cause:Event = null):void Opens or closes a branch item. |
| 4 | getParentItem(item:Object):* Returns the known parent of a child item. |
| 5 | isItemOpen(item:Object):Boolean Returns true if the specified item branch is open (is showing its children). |
| 6 | setItemIcon(item:Object, iconID:Class, iconID2:Class):void Sets the associated icon for the item. |
Protected methods
| S.N. | Method & Description |
|---|---|
| 1 | dragCompleteHandler(event:DragEvent):void [override] Handles DragEvent.DRAG_COMPLETE events. |
| 2 | dragDropHandler(event:DragEvent):void [override] Handles DragEvent.DRAG_DROP events. |
| 3 | initListData(item:Object, treeListData:mx.controls.treeClasses:TreeListData):void Initializes a TreeListData object that is used by the tree item renderer. |
| 4 | makeListData(data:Object, uid:String, rowNum:int):BaseListData [override] Creates a new TreeListData instance and populates the fields based on the input data provider item. |
Events
| S.N. | Event & Description |
|---|---|
| 1 | itemClose Dispatched when a branch is closed or collapsed. |
| 2 | itemOpen Dispatched when a branch is opened or expanded. |
| 3 | itemOpening Dispatched when a branch open or close is initiated. |
Methods inherited
This class inherits methods from the following classes:
mx.controls.List
mx.controls.listClasess.ListBase
mx.core.ScrollControlBase
mx.core.UIComponent
mx.core.FlexSprite
flash.display.Sprite
flash.display.DisplayObjectContainer
flash.display.InteractiveObject
flash.display.DisplayObject
flash.events.EventDispatcher
Object
Flex Tree Control Example
Let us follow the following steps to check usage of Tree control in a Flex application by creating a test application:
| Step | Description |
|---|---|
| 1 | Create a project with a name HelloWorld under a package com.tutorialspoint.client as explained in the Flex - Create Application chapter. |
| 2 | Modify HelloWorld.mxml as explained below. Keep rest of the files unchanged. |
| 3 | Compile and run the application to make sure business logic is working as per the requirements. |
Following is the content of the modified mxml file src/com.tutorialspoint/HelloWorld.mxml.
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"
width="100%" height="100%" minWidth="500" minHeight="500"
>
<fx:Style source="/com/tutorialspoint/client/Style.css"/>
<fx:Script>
<![CDATA[
[Bindable]
public var selectedNode:XML;
// Event handler for the Tree control change event.
public function treeChanged(event:Event):void {
selectedNode=Tree(event.target).selectedItem as XML;
}
]]>
</fx:Script>
<fx:Declarations>
<fx:XMLList id="treeData">
<node label="E-Mail Box">
<node label="Inbox">
<node label="Client"/>
<node label="Product"/>
<node label="Personal"/>
</node>
<node label="Sent Items">
<node label="Professional"/>
<node label="Personal"/>
</node>
<node label="Deleted Items"/>
<node label="Spam"/>
</node>
</fx:XMLList>
</fx:Declarations>
<s:BorderContainer width="630" height="480" id="mainContainer"
styleName="container">
<s:VGroup width="100%" height="100%" gap="50"
horizontalAlign="center" verticalAlign="middle">
<s:Label id="lblHeader" text="Complex Controls Demonstration"
fontSize="40" color="0x777777" styleName="heading"/>
<s:Panel id="treePanel" title="Using Tree"
width="500" height="300">
<s:layout>
<s:VerticalLayout gap="10" verticalAlign="middle"
horizontalAlign="center"/>
</s:layout>
<mx:Tree id="tree" width="95%" height="75%"
labelField="@label" showRoot="false"
dataProvider="{treeData}" change="treeChanged(event)"/>
<s:TextArea height="20%" width="95%"
text="Selected Item: {selectedNode.@label}"/>
</s:Panel>
</s:VGroup>
</s:BorderContainer>
</s:Application>
Once you are ready with all the changes done, let us compile and run the application in normal mode as we did in Flex - Create Application chapter. If everything is fine with your application, this will produce following result: [ Try it online ]
