Flex2中，DataGrid如果我们没有指定columns熟悉的话，DataGrid会自动根据dataProvider的各行数据的属性名隐式自动地创建列，例如如下代码：
<?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);
}
