Flex2 发现之旅：动态创建DataGrid列

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.macromedia.com/2005/mxml" xmlns="*"
  layout="vertical" creationComplete="loadDgView()">
<mx:Script>
   <![CDATA[
     [Bindable]
     public var works:Array= [
         { id: 1, name: ’feiy’, sex: ’male’},
         { id: 2, name: ’wenj’, sex: ’fmale’}];
     private var worksColumns:Array= [
       { columnName: "id",headerText: "work’s id",width: 100},
       { columnName: "name",headerText: "work’s name",width: 200},
       { columnName: "sex",headerText: "work’s sex",width: 100}];
     [Bindable]
     public var departments:Array=[
       { id: 1, name: ’tech dept.’},
       { id: 2, name: ’service dept.’}];
     private var departmentsColumns:Array= [
       { columnName: "id",headerText: "department’s id",width: 200},
       { columnName: "name",headerText: "department’s name",width:200}];
     private function loadDgView(){
       if(type_cb.selectedIndex==0){
         view_dg.dataProvider=works;
       }else{
         view_dg.dataProvider=departments;
       }
     }
   ]]>
</mx:Script>
<mx:HBox>
   <mx:ComboBox id="type_cb" change="loadDgView()">
     <mx:dataProvider>
       <mx:Array>
         <mx:Object label="works"/>
         <mx:Object label="departments"/>
       </mx:Array>
     </mx:dataProvider>
   </mx:ComboBox>
</mx:HBox>
<mx:DataGrid id="view_dg" />
</mx:Application>

　　当我们选择works时，DataGrid自动根据dataProvider：works数组中的数据生成三列的DataGridColumn；而选择departments时，又相应的变更为两列，非常的方便。
DataGrid组件的这一功能是Flex1.5中所不具有的，是Flex2中的一大改进。
但是如果我们DataGrid的表头与列明不一致的时候，或者我们并不需要显示每行所有的数据，这时候DataGrid的隐式自动创建列的方法就不再适用了，这时候，我们就需要自己手动来创建列。
DataGrid使用columns属性来标识列信息，column属性是一个mx.controls.gridclasses.DataGridColumn数组，所以要动态创建表格列，只需要创建一个DataGridColumn数组，然后将其赋值给DataGrid的columns属性就可以了。前面示例的代码，我们改进如下：

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.macromedia.com/2005/mxml" xmlns="*"
  layout="vertical" creationComplete="loadDgView()">
<mx:Script>
   <![CDATA[
     import mx.controls.gridclasses.DataGridColumn;

     [Bindable]
     public var works:Array= [
         { id: 1, name: ’feiy’, sex: ’male’},
         { id: 2, name: ’wenj’, sex: ’fmale’}];
     private var worksColumns:Array= [
       { columnName: "id",headerText: "work’s id",width: 100},
       { columnName: "name",headerText: "work’s name",width: 200},
       { columnName: "sex",headerText: "work’s sex",width: 100}];
     [Bindable]
     public var departments:Array=[
       { id: 1, name: ’tech dept.’},
       { id: 2, name: ’service dept.’}];
     private var departmentsColumns:Array= [
       { columnName: "id",headerText: "department’s id",width: 200},
       { columnName: "name",headerText: "department’s name",width:200}];
     private function loadDgView(){
       if(type_cb.selectedIndex==0){
         var columns:Array=new Array();
         for(var i:int;i<worksColumns.length;i++){
           var item:Object=worksColumns[i];
           var dgColumn:DataGridColumn=new DataGridColumn();
           dgColumn.columnName=item.columnName;
           dgColumn.headerText=item.headerText;
           dgColumn.width=item.width;
           columns.push(dgColumn);
         }
         view_dg.columns=columns;
         view_dg.dataProvider=works;
       }else{
         var columns:Array=new Array();
         for(var i:int;i<departmentsColumns.length;i++){
           var item:Object=departmentsColumns[i];
           var dgColumn:DataGridColumn=new DataGridColumn();
           dgColumn.columnName=item.columnName;
           dgColumn.headerText=item.headerText;
           dgColumn.width=item.width;
           columns.push(dgColumn);
         }
         view_dg.columns=columns;
         view_dg.dataProvider=departments;
       }
     }
   ]]>
</mx:Script>
<mx:HBox>
   <mx:ComboBox id="type_cb" change="loadDgView()">
     <mx:dataProvider>
       <mx:Array>
         <mx:Object label="works"/>
         <mx:Object label="departments"/>
       </mx:Array>
     </mx:dataProvider>
   </mx:ComboBox>
</mx:HBox>
<mx:DataGrid id="view_dg" />
</mx:Application>