世风十三

今天，发现一个Flex的Bug：
当你设置一个DataGrid的 showHeaders="false"，则当你在<mx:DataGridColumn/>中设置backgroundColor样式时会报错：
TypeError: Error #1010: A term is undefined and has no properties.
    at mx.controls::DataGrid/drawColumnBackground()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\controls\DataGrid.as:3012]
    at mx.controls::DataGrid/drawLinesAndColumnGraphics()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\controls\DataGrid.as:3311]
    at mx.controls::DataGrid/drawLinesAndColumnBackgrounds()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\controls\DataGrid.as:3207]
……
查看了DataGrid的源代码，发现是在drawColumnBackground方法中用到了columnHeader对象，而这时可能因为showHeaders="false"而columnHeader没有相应的属性值了。

因为是要写一个最后一列没有边框的DataGrid，所以就继承并改写了DataGrid，另外写了个方法：
         protected function drawColumnBackgroundX(s:Sprite, columnIndex:int, columnX:Number, color:uint, column:DataGridColumn):void {
            var background:Shape;
            background = Shape(s.getChildByName(columnIndex.toString()));

            if(!background) {
                background = new FlexShape();
                s.addChild(background);
                background.name = columnIndex.toString();
            }

            var g:Graphics = background.graphics;
            g.clear();
            g.beginFill(color);

            var lastRow:Object = rowInfo[listItems.length - 1];
//            var columnHeader:DataGridHeader = (s.parent == lockedColumnContent) ? DataGridHeader(lockedColumnHeader) : DataGridHeader(header);

//            var xx:Number = columnHeader.rendererArray[columnIndex].x
            var xx:Number = columnX;
            var yy:Number = rowInfo[0].y;

            // Height is usually as tall is the items in the row, but not if
            // it would extend below the bottom of listContent
            var height:Number = Math.min(lastRow.y + lastRow.height, listContent.height - yy);

            g.drawRect(xx, yy, column.width, listContent.height - yy);
            g.endFill();
        }

同时改写drawLinesAndColumnGraphics(contentHolder:ListBaseContentHolder, visibleColumns:Array, separators:Object)，在其中使用：drawColumnBackgroundX(colBGs, i, xx, Number(bgCol), col);来渲染背景色。