asdoc/mx/controls/listClasses/IDropInListItemRenderer.js.json

{ "type": "interface",
  "qname": "mx.controls.listClasses.IDropInListItemRenderer",
"baseInterfaceNames": [
"org.apache.royale.core.IListDataItemRenderer"]
,
    "description": "The interface for &quot;drop-in&quot; item renderers.  Most IListItemRenderers are not &quot;drop-ins&quot;.  They are expecting to use a particular field of the data provider item.  For example, they may assign the &quot;lastName&quot; property of the item to a Label's <code>text</code> property.  This is easy to write using data-binding, but has the negative consequence that the renderer cannot be re-used in another column of a DataGrid or another List with different fields. IDropInListItemRenderer allows a renderer to be re-used.  The list classes will pass more information to the renderer so that it can determine which field to use at run-time.  <p>Components that you want to use as drop-in item renderers or drop-in item editors  must implement the IDropInListItemRenderer interface. Many Flex component implement this interface, and therefore are usable as drop-in item renderers and drop-in item editors in any column or list.</p>  <p>Drop-in item renderers or drop-in item editors also must implement the IDataRenderer interface to define the <code>data</code> property.</p>  <p>When a component is used as a drop-in item renderer or drop-in item editor, Flex initializes the <code>listData</code> property of the component with the appropriate data from the list control. The component can then use the <code>listData</code> property to initialize the <code>data</code> property of the drop-in item renderer or drop-in item editor.</p>  <p>The <code>listData</code> property is of type BaseListData, where the BaseListData class has four subclasses: DataGridListData, ListData, TreeListData, and MenuListData. The actual data type of the value of the <code>listData</code> property depends on the control using the drop-in item renderer or item editor. For a DataGrid control, the value is of type DataGridListData, for a List control the value is of type ListData, for a Tree control, the value is of type TreeListData, and for a Menu control, the value is of type MenuListData..</p>  <p>The following example shows the setter method for the <code>data</code> property for the NumericStepper control that initializes NumericStepper's <code>value</code> property based on the value of the <code>listData</code> property:</p>  <pre>\\n public function set data(value:Object):void\\n {\\n _data = value;\\n \\n this.value = _listData ? parseFloat(_listData.label) : Number(_data);\\n \\n dispatchEvent(new FlexEvent(FlexEvent.DATA_CHANGE));\\n }\\n </pre>  <p>In the example above, the NumericStepper control ignores the <code>data</code> property  when setting NumericStepper's <code>value</code> property, and uses the <code>listData</code> property instead.</p>  <p>To implement the IDropInListItemRenderer interface, you define a setter and getter method to implement the <code>listData</code> property. Typically, the setter method writes the value of the <code>listData</code> property to an internal variable. The list class always assigns this property then sets the data provider item in the <code>data</code> property.</p>  <p>Notice that the setter method for the <code>listData</code> property does not dispatch an event. This is because the list classes always set <code>listData</code>, then set the <code>data</code> property. Setting the <code>data</code> property also dispatches the <code>dataChange</code> event. You never set <code>listData</code> on its own, so it does not need to dispatch its own event. </p>  <p>The <code>data</code> setter method could call the <code>invalidateProperties()</code> method if it did something that required the control to update itself. It would then be up to the component developer to write a <code>commitProperties()</code> method to determine that <code>listData</code> was modified, and handle it accordingly. </p>  <p>The getter method returns the current value of the internal variable,  as the following example shows:</p>  <pre>\\n // Internal variable for the property value.\\n private var _listData:BaseListData;\\n \\n // Make the listData property bindable.\\n [Bindable(&quot;dataChange&quot;)]\\n \\n // Define the getter method.\\n public function get listData():BaseListData\\n {\\n return _listData;\\n }\\n \\n // Define the setter method,\\n public function set listData(value:BaseListData):void\\n {\\n _listData = value;\\n }\\n </pre>",
  "tags": [
  {  "tagName": "see",
         "values": ["mx.controls.listClasses.BaseListData", "mx.core.IDataRenderer"]},
      {  "tagName": "playerversion",
         "values": ["Flash 9", "AIR 1.1"]},
      {  "tagName": "productversion",
         "values": ["Flex 3"]},
      {  "tagName": "langversion",
         "values": ["3.0"]}  ]}