Full code after the jump.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/16/aligning-the-header-text-in-a-datagrid-column-in-flex/ -->
<mx:Application name="DataGrid_headerStyleName_textAlign_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.events.ListEvent;

            private function comboBox_change(evt:ListEvent):void {
                var value:String = comboBox.selectedItem.toString();
                var styleName:String = "." + dataGrid.getStyle("headerStyleName");
                var cssDecl:CSSStyleDeclaration = StyleManager.getStyleDeclaration(styleName);
                cssDecl.setStyle("textAlign", value);
            }
        ]]>
    </mx:Script>

    <mx:XML id="dp" source="data/products.xml" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="textAlign:">
                <mx:ComboBox id="comboBox"
                        dataProvider="[left,center,right,justify]"
                        change="comboBox_change(event);" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:DataGrid id="dataGrid"
            dataProvider="{dp.product}"
            rowCount="5"
            verticalScrollPolicy="on"
            width="300">
        <mx:columns>
            <mx:DataGridColumn id="dataGridColumn1"
                    dataField="@name"
                    headerText="This is a column with a long title:"
                    headerWordWrap="true"
                    minWidth="80" />
            <mx:DataGridColumn id="dataGridColumn2"
                    dataField="@price"
                    headerText="Price:"
                    headerWordWrap="false"
                    minWidth="20" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>

View source is enabled in the following example.

You can also set the text alignment in an external .CSS file or <mx:Style /> block, as seen in the following example:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/16/aligning-the-header-text-in-a-datagrid-column-in-flex/ -->
<mx:Application name="DataGrid_headerStyleName_textAlign_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Style>
        DataGrid {
            headerStyleName: centerBold;
        }

        .centerBold {
            fontWeight: bold;
            textAlign: center;
        }
    </mx:Style>

    <mx:XML id="dp" source="data/products.xml" />

    <mx:DataGrid id="dataGrid"
            dataProvider="{dp.product}"
            rowCount="5"
            verticalScrollPolicy="on"
            width="300">
        <mx:columns>
            <mx:DataGridColumn id="dataGridColumn1"
                    dataField="@name"
                    headerText="This is a column with a long title:"
                    headerWordWrap="true"
                    minWidth="80" />
            <mx:DataGridColumn id="dataGridColumn2"
                    dataField="@price"
                    headerText="Price:"
                    headerWordWrap="false"
                    minWidth="20" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>

Due to popular demand, here is the “same” example in a more ActionScript friendly format:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/16/aligning-the-header-text-in-a-datagrid-column-in-flex/ -->
<mx:Application name="DataGrid_headerStyleName_textAlign_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white"
        initialize="init();">

    <mx:Script>
        <![CDATA[
            import flash.text.TextFormatAlign;

            import mx.containers.ApplicationControlBar;
            import mx.containers.Form;
            import mx.containers.FormItem;
            import mx.controls.ComboBox;
            import mx.controls.DataGrid;
            import mx.controls.dataGridClasses.DataGridColumn;
            import mx.core.ScrollPolicy;
            import mx.events.ListEvent;

            private const XML_URL:String = "data/products.xml";

            private var urlLoader:URLLoader;
            private var dp:XML;
            private var comboBox:ComboBox;
            private var dataGrid:DataGrid;
            private var dataGridColumn1:DataGridColumn;
            private var dataGridColumn2:DataGridColumn;

            private function init():void {
                urlLoader = new URLLoader();
                urlLoader.addEventListener(Event.COMPLETE,
                            urlLoader_complete);
                urlLoader.load(new URLRequest(XML_URL));

                var arr:Array = [];
                arr.push(TextFormatAlign.LEFT);
                arr.push(TextFormatAlign.CENTER);
                arr.push(TextFormatAlign.RIGHT);
                arr.push(TextFormatAlign.JUSTIFY);

                comboBox = new ComboBox();
                comboBox.dataProvider = arr;
                comboBox.addEventListener(ListEvent.CHANGE,
                            comboBox_change);

                var formItem:FormItem = new FormItem();
                formItem.label = "textAlign:";
                formItem.addChild(comboBox);

                var form:Form = new Form();
                form.styleName = "plain";
                form.addChild(formItem);

                var appControlBar:ApplicationControlBar;
                appControlBar = new ApplicationControlBar();
                appControlBar.dock = true;
                appControlBar.addChild(form);
                addChildAt(appControlBar, 0);

                dataGridColumn1 = new DataGridColumn("@name");
                dataGridColumn1.headerText = "This is a column with a long title:";
                dataGridColumn1.headerWordWrap = true;
                dataGridColumn1.minWidth = 80;

                dataGridColumn2 = new DataGridColumn("@price");
                dataGridColumn2.headerText = "Price:";
                dataGridColumn2.headerWordWrap = false;
                dataGridColumn2.minWidth = 20;

                dataGrid = new DataGrid();
                dataGrid.rowCount = 5;
                dataGrid.verticalScrollPolicy = ScrollPolicy.ON;
                dataGrid.width = 300;
                dataGrid.columns = [dataGridColumn1, dataGridColumn2];
                addChild(dataGrid);
            }

            private function urlLoader_complete(evt:Event):void {
                dataGrid.dataProvider = XML(evt.target.data).product;
            }

            private function comboBox_change(evt:ListEvent):void {
                var value:String = comboBox.selectedItem.toString();
                var styleName:String = "." + dataGrid.getStyle("headerStyleName");
                var cssDecl:CSSStyleDeclaration;
                cssDecl = StyleManager.getStyleDeclaration(styleName);
                cssDecl.setStyle("textAlign", value);
            }
        ]]>
    </mx:Script>

</mx:Application>

 

Full code after the jump.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/14/toggling-word-wrap-on-a-datagrid-column-header-in-flex/ -->
<mx:Application name="DataGridColumn_headerWordWrap_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="top"
        backgroundColor="white">

    <mx:XML id="dp" source="data/products.xml" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="headerWordWrap:">
                <mx:CheckBox id="checkBox" />
            </mx:FormItem>
            <mx:FormItem label="rowCount:">
                <mx:HSlider id="slider"
                        minimum="2"
                        maximum="10"
                        value="6"
                        snapInterval="1"
                        tickInterval="1"
                        liveDragging="true"
                        showTrackHighlight="true" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:DataGrid id="dataGrid"
            dataProvider="{dp.product}"
            rowCount="{slider.value}"
            verticalScrollPolicy="on"
            width="300">
        <mx:columns>
            <mx:DataGridColumn id="dataGridColumn1"
                    dataField="@name"
                    headerText="This is a column with a long title:"
                    headerWordWrap="{checkBox.selected}"
                    minWidth="80" />
            <mx:DataGridColumn id="dataGridColumn2"
                    dataField="@price"
                    headerText="Price:"
                    headerWordWrap="false"
                    minWidth="20" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>

And the XML file, data/products.xml, is as follows:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/14/toggling-word-wrap-on-a-datagrid-column-header-in-flex/ -->
<products>
	<product name="Product 1" price="1.99" />
	<product name="Product 2" price="2.99" />
	<product name="Product 3" price="3.99" />
	<product name="Product 4" price="4.99" />
	<product name="Product 5" price="5.99" />
	<product name="Product 6" price="6.99" />
	<product name="Product 7" price="7.99" />
	<product name="Product 8" price="8.99" />
	<product name="Product 9" price="9.99" />
	<product name="Product 0" price="0.99" />
</products>

View source is enabled in the following example.

You can also set the headerWordWrap property using ActionScript, as seen in the following example:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/14/toggling-word-wrap-on-a-datagrid-column-header-in-flex/ -->
<mx:Application name="DataGridColumn_headerWordWrap_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="top"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            private function checkBox_change(evt:Event):void {
                dataGridColumn1.headerWordWrap = checkBox.selected;
            }
        ]]>
    </mx:Script>

    <mx:XML id="dp" source="data/products.xml" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="headerWordWrap:">
                <mx:CheckBox id="checkBox"
                        change="checkBox_change(event);" />
            </mx:FormItem>
            <mx:FormItem label="rowCount:">
                <mx:HSlider id="slider"
                        minimum="2"
                        maximum="10"
                        value="6"
                        snapInterval="1"
                        tickInterval="1"
                        liveDragging="true"
                        showTrackHighlight="true" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:DataGrid id="dataGrid"
            dataProvider="{dp.product}"
            rowCount="{slider.value}"
            verticalScrollPolicy="on"
            width="300">
        <mx:columns>
            <mx:DataGridColumn id="dataGridColumn1"
                    dataField="@name"
                    headerText="This is a column with a long title:"
                    minWidth="80" />
            <mx:DataGridColumn id="dataGridColumn2"
                    dataField="@price"
                    headerText="Price:"
                    headerWordWrap="false"
                    minWidth="20" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>

Due to popular demand, here is the “same” example in a more ActionScript friendly format:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/14/toggling-word-wrap-on-a-datagrid-column-header-in-flex/ -->
<mx:Application name="DataGridColumn_headerWordWrap_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="top"
        backgroundColor="white"
        initialize="init();">

    <mx:Script>
        <![CDATA[
            import mx.containers.ApplicationControlBar;
            import mx.containers.Form;
            import mx.containers.FormItem;
            import mx.controls.CheckBox;
            import mx.controls.DataGrid;
            import mx.controls.HSlider;
            import mx.controls.dataGridClasses.DataGridColumn;
            import mx.core.ScrollPolicy;
            import mx.events.SliderEvent;

            private var checkBox:CheckBox;
            private var slider:HSlider;
            private var dataGrid:DataGrid;
            private var dataGridColumn1:DataGridColumn;
            private var dataGridColumn2:DataGridColumn;

            private function init():void {
                checkBox = new CheckBox();
                checkBox.addEventListener(Event.CHANGE,
                            checkBox_change);

                slider = new HSlider();
                slider.minimum = 2;
                slider.maximum = 10;
                slider.value = 6;
                slider.snapInterval = 1;
                slider.tickInterval = 1;
                slider.liveDragging = true;
                slider.setStyle("showTrackHighlight", true);
                slider.addEventListener(SliderEvent.CHANGE,
                            slider_change);

                var formItem1:FormItem = new FormItem();
                formItem1.label = "headerWordWrap:";
                formItem1.addChild(checkBox);

                var formItem2:FormItem = new FormItem();
                formItem2.label = "rowCount:";
                formItem2.addChild(slider);

                var form:Form = new Form();
                form.styleName = "plain";
                form.addChild(formItem1);
                form.addChild(formItem2);

                var appControlBar:ApplicationControlBar;
                appControlBar = new ApplicationControlBar();
                appControlBar.dock = true;
                appControlBar.addChild(form);
                addChildAt(appControlBar, 0);

                dataGridColumn1 = new DataGridColumn();
                dataGridColumn1.dataField = "@name";
                dataGridColumn1.headerText = "This is a column with a long title:";
                dataGridColumn1.minWidth = 80;

                dataGridColumn2 = new DataGridColumn();
                dataGridColumn2.dataField = "@price";
                dataGridColumn2.headerText = "Price:";
                dataGridColumn2.headerWordWrap = false;
                dataGridColumn2.minWidth = 20;

                dataGrid = new DataGrid();
                dataGrid.columns = [dataGridColumn1, dataGridColumn2];
                dataGrid.dataProvider = dp.product;
                dataGrid.rowCount = 6;
                dataGrid.verticalScrollPolicy = ScrollPolicy.ON;
                dataGrid.width = 300;
                addChild(dataGrid);
            }

            private function checkBox_change(evt:Event):void {
                dataGridColumn1.headerWordWrap = checkBox.selected;
            }

            private function slider_change(evt:SliderEvent):void {
                dataGrid.rowCount = evt.value;
            }
        ]]>
    </mx:Script>

    <mx:XML id="dp" source="data/products.xml" />

</mx:Application>